Search

This study employed simple polystyrene-coated magnetite nanoparticles (PS@MNPs)–assisted batch adsorption process for the removal of two antidepressant active ingredients (amitriptyline HCl and sertraline HCl) from hospital wastewater. Dominant parameters of the adsorption process including pH, adsorbent amount, and contact period were optimized through the univariate approach to enhance the adsorption efficiency. Upon reaching optimum adsorption conditions, equilibrium experiments were performed by spiking the adsorbates in hospital wastewater in the concentration range of 100–2000 μg/L. The concentrations of the adsorbates in the effluent were calculated using the matrix-matching calibration strategy to enhance the accuracy of quantification. A validated switchable solvent-based liquid phase microextraction (SS-LPME) method was employed to enrich the two active pharmaceutical ingredients (APIs) prior to sensitive determination with GC-MS (gas chromatography-mass spectrometry). The equilibrium data were mathematically modeled employing the Langmuir and Freundlich adsorption isotherm models. The isotherm constants were calculated, and the results showed that both the isotherm models fitted well with the experimental data. The efficient and simple batch adsorption strategy reported in this study was successfully employed to remove amitriptyline HCl and sertraline HCl from hospital wastewater at low concentrations. [ABSTRACT FROM AUTHOR]

The main objective of this study was to optimize the adsorption process of methylene blue on a natural, low-cost adsorbent, Leonurus cardiaca L. biomass powder, in order to maximize dye removal efficiency from aqueous solutions. For this purpose, the Taguchi method was used based on an L27 orthogonal array design considering six controllable factors at three levels. The percentage contribution of each factor was computed using analysis of variance (ANOVA). The optimal adsorption conditions were established. The experimental data from equilibrium and kinetic studies were modelled using specific equilibrium isotherms and kinetic models. Thermodynamic parameters were calculated in order to determine the main adsorption mechanism. The obtained results showed that the ionic strength is the factor that most influences dye adsorption (percentage contribution 72.33%), whereas the adsorbent dose had the least impact. The Sips isotherm and the general kinetic model most accurately characterized the process. The maximum adsorption capacity 103.21 (mg g−1) indicated by the Sips isotherm and the equilibrium time (40 min) were better compared to the values obtained for other bio-adsorbents used for methylene blue adsorption. The main mechanism involved in the adsorption is physisorption, while chemisorption only contributes marginally to the process. [ABSTRACT FROM AUTHOR]

The present study investigates the feasibility of adsorption method for the removal of Di-n-butyl phosphate from sodium carbonate solution on adsorbents such as XAD-4 and XAD-7. The fundamental aspects of equilibrium and kinetics of adsorption have been studied. The experimental equilibrium data were fitted well with Sips isotherm, and maximum solid uptake capacity for monolayer coverage (qm) was found to be 0.363 × 10−3 mol/g and 0.385 × 10−3 mol/g for XAD-4 and XAD-7, respectively. The adsorption kinetics was well described by the pseudo-first-order model, and estimated first-order rate constant values were found to be 0.041 min−1 for XAD-4 and 0.027 min−1 for XAD-7. The transport mechanism of solute from the bulk solution to adsorbent was described in detail with suitable mathematical model, and experimental kinetic data were superimposed on numerically solved concentration profiles to calculate external mass transfer coefficient (kf) and effective diffusivity (De). The values of kf and De were estimated as 4.632 × 10−7 m/s and 8.849 × 10−13 m2/s, respectively, for XAD-4, whereas for XAD-7, the values were found to be 2.132 × 10−6 m/s and 1.389 × 10−12 m2/s. XAD-7 is found to have slightly better adsorption capacity and transport characteristics than XAD-4. [ABSTRACT FROM AUTHOR]

Even in the current period, ecologists and industrialists still need help removing heavy metals from their sources, such as industrial wastes and wastewater. This work aimed to determine the appropriate mass for metal adsorption utilising groundnut shells to remove Pb and Cd ions from industrial effluent. The heavy metal adsorption rate was also analysed as a function of pH, absorbent mass, contact duration, initial metal ion concentration, and temperature. According to the results, the best forms for the adsorption of Pb2+ and Cd2+were a pH of 6.0, a biomass weight of 0.5 g, a temperature of 65°C, an initial concentration of metal of less than 100 mg/dm3, and 30 minutes contact time. The research found that variations in these parameters, above or below their ideal range, influenced the absorption rate of Pb2+ and Cd2+ by groundnut shell absorbent. Analysis of the isotherms showed that the Langmuir isotherm was the best match. The adsorption process followed the pseudo-second-order kinetics. It was determined that groundnut shells could be employed as a cost-efficient and eco-friendly acceptable adsorbent in treating wastewater containing toxic metals. [ABSTRACT FROM AUTHOR]

In this study, facile synthesis of α-Fe2O3 biocomposite was mediated by cassava starch as a soft template. Batch mode evaluated its sorption behavior for fluoride removal from aqueous media. Characterization studies using analytical techniques confirmed the existence of porous α- Fe2O3 biocomposite with heterogeneous surfaces having a varied affinity for fluoride. The sorption process was optimized using central composite design (CCD) in response surface methodology (RSM) with a good model prediction (R2 = 0.9066). A study of the interaction effect showed the synergy of process variables on fluoride removal with the result's intensity indicated by the nature of contour plot curvature. Based on the RSM optimization, an optimum fluoride removal efficiency of 85.26 % can be achieved at an initial fluoride concentration of 55 mg/L, α- Fe2O3 biocomposite dose of 0.55 g, pH of 7.5, and contact time of 95 min. Sorption equilibrium data were well modeled by Freundlich isotherm (0.9916), indicating multilayer sorption on a heterogeneous surface of the sorbent with a varied affinity for fluoride. Presence of co-existing anions reduced fluoride removal efficiency in the order PO43− > HCO3− > SO42− > NO3− > CƖ− . At the same time, its kinetics was better modeled by pseudo-second-order kinetics (R2 = 0.9764), showing that the sorption process is rate-limiting. The sorption thermodynamics study showed that the process was spontaneous, exothermic, and entropy-driven physisorption. Hence, the results signify that the green synthesized α- Fe2O3 biocomposite could be a potential sorbent for sustainable defluoridation.

This study aims to investigate the kinetics, isotherms, and thermodynamics of methylene blue (MB) dye adsorption from aqueous solution onto activated carbon prepared from orange peel waste (PO). This material was chemically treated with sulfuric acid, pyrolyzed, and activated in microwave apparatus under nitrogen flow. The resulting activated carbon was supported using cobalt transition metal by a wet impregnation process at different cobalt (Co) contents; the optimum condition was achieved at cobalt impregnations of 20 wt.%. The supported carbon Co20 wt.%-POAC catalyst was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, and Brunauer-Emmett-Teller surface area analysis. The results show that the equilibrium was reached at 270 min with an adsorption capacity of 27 mg·g-1; the Langmuir isotherm was the best model that describes the experimental data. Besides, the pseudo-first-order adsorption model best depicts the adsorption kinetics of the MB by Co20 wt.%-POAC. Thermodynamic analysis shows that the standard Gibb's free energy change (G) has negative values, confirming, therefore, the feasibility and spontaneity of the process. The changes in enthalpy (H°) and entropy (S°) were found to be -2,011 J·mol-1 and18.9 J·K-1·mol-1, respectively. Finally, our results revealed that grafting cobalt onto the surface of the orange peel-activated carbon improves its adsorption capacity, and hence its efficiency in removing MB from wastewater. [ABSTRACT FROM AUTHOR]

Hexavalent chromium (Cr VI) has mutagenic and carcinogenic properties and causes severe health and environmental effects. The chromium's adsorption equilibrium in aqueous media, its mechanisms, and different lignocellulosic wastes have been studied by many researchers. In this way, this paper provides a systematic, updated, and critical overview of Cr (IVI) adsorption by lignocellulosic waste adsorbent. Besides, analyzing the Cr (VI) problems in the aquatic environment addressed to lignocellulosic waste and its properties as adsorbent. Also, it was made a deep revision about important topics such as chemical regeneration and Cr (VI) recovery, characterization techniques, and interfering factors effects (e.g., pH, dosage). In addition, it was studied carefully the adsorption phenomena through several mathematical models of kinetics and isotherms and analyzed the thermodynamics results reported by an important number of research papers. Through this review, it was observed that the lignocellulosic wastes adsorption capacities usually range from 0.32 to 403.23 mg g−1, the adsorbent percentage removal after regenerating cycle ranged between 26.5 and 98.69%, and a greater performance of removing Cr (VI) occurs at pH range 1–6. The pseudo-second-order and Langmuir models were the models that presented the best adjustment of the experimental data for Cr (VI) adsorption, and the thermodynamic nature was spontaneous and endothermic for most cases. Further studies about lignocellulosic waste adsorbents lifecycle, stability, large-scale production, and production cost analysis are still necessary to determine the stability and efficacy of lignocellulosic wastes adsorbents in real effluent treatment. [ABSTRACT FROM AUTHOR]

This study describes a new strain of Staphylococcus sciuri as a novel bacterium for Cr(VI) removal. Dried cells of the bacterium showed complete removal of 30 mg/l Cr(VI) within 9 h at 40 °C and pH 2.0. The experimental data in the Cr(VI) concentration range of 30-100 mg/l fitted well with the pseudo-second order kinetic model and Langmuir isotherm (R² = 0.9724 and maximum adsorption capacity of 120.48 mg/g). The rate of Cr(VI) adsorption was best described by a Boyd plot and the intraparticle diffusion model. X-ray photoelectron spectroscopy suggested that S. sciuri used carbon and oxygen functional groups for binding Cr(VI). The quick removal of Cr(VI) in this study supports application of S. sciuri to reduce Cr(VI) environmental risk. [ABSTRACT FROM AUTHOR]

Batch adsorption experiments were carried out to study the removal of the toxic Methylene Blue Dye (MBD) from synthetic aqueous solutions using the nanoparticles form of Arthrospira platensis NIOF17/003. The adsorption capacity of the adsorbent for MBD was investigated using different amounts of A. platensis nanoparticles at different contact times, temperatures, pH, and MBD initial concentrations in the synthetic aqueous solution. In addition, A. platensis nanoparticles were characterized using Electron Microscopy (SEM), Brunauer–Emmett–Teller (BET), Fourier Transform Infrared (FTIR), and Ultraviolet spectra (UV) techniques. The optimum removal of MBD was found at a concentration of 0.4 g A. platensis nanoparticles. A. platensis nanoparticles remove 93% of MBD in 5 min (under agitation conditions at 150 rpm). The highest adsorption capacity was found by the Langmuir model to be 58.8 mg g−1. It is an endothermic process with spontaneity increasing with temperature. The probable mechanism for the adsorption is chemisorption via surface-active charges in the initial phase, which is followed by physical sorption by occupying pores of A. platensis. MBD adsorption by A. platensis follows pseudo-second-order kinetics. The Freundlich and Langmuir models fit well with the experimental data. The adsorption experiments suggested that the regeneration of the adsorbents was possible for repeated use, especially regarding MBD up to 65.8% after three cycles, which proves it can be easily recycled. In conclusion, the nanoparticles of A. platensis have a significant adsorption potential in the removal of MBD from effluent wastewater. [ABSTRACT FROM AUTHOR]

Abstract This article describes how selectively anionic organic molecules could be removed from aqueous medium using naturally available gypsum (GS) adsorbent. Gypsum (CaSO4.2H2O) shows strong interactions with anionic dye molecules while it dos not show any affinity towards cationic dye molecules. We have shown the removal efficiency of gypsum taking chlorazole yellow (anionic dye) and methylene blue (cationic dye) as examples of adsorbates. The GS has been to be even more effective than activated carbon in attaining chlorazole yellow (CY) removal. Three well-known kinetic equations e.g. pseudo-first-order, pseudo-second order and intraparticle diffusion were exploited to interpret the experimental data. Results show best fitting with second order kinetic process with excellent regression coefficient (r 2 = 0.99) for the adsorption process. The equilibrium data were analyzed exploiting some adsorption isotherm models. It was apparent that the Freundlich isotherm model superbly fitted for CY dye adsorption process. And the maximum adsorption capacity, Q m, was obtained as 12.85 mg g−1 at room temperature. The negative values of Gibb’s free energy change (ΔG o) suggests that the CY dye molecule adsorption process is spontaneous in nature. Moreover, negative enthalpy change (ΔH o) indicates the exothermic nature of the adsorption process. The outcome could be exploited where anionic organic molecules are required to be separated, selectively.

The dried form of the brown seaweed Sargassum latifolium was tested for its ability to remove toxic Methylene Blue Dye (MBD) ions from aqueous synthetic solutions and industrial wastewater effluents. In a batch adsorption experiment, different initial concentrations of MBD (5, 10, 20, 30, and 40 mg L−1), sorbent dosages (0.025, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5 g L−1), contact time (5, 10, 15, 30, 60, 120 min), pH (3, 5, 8, 10, and 12), and temperature (30, 40, 50, 60 °C) were observed. Dried powder of S. latifolium was characterized before and after adsorption of MBD using different techniques, such as FTIR, SEM, UV visible spectral examination, and BET techniques. The BET surface area suggests the formation of S. latifolium was 111.65 m2 g−1, and the average pore size was 2.19 nm. The obtained results showed that at an MBD concentration of 40 mg L−1, the adsorption was rapid in the first 5, 10, and 15 min of contact time, and an equilibrium was reached in about 60 and 120 min for the adsorption. At the optimum temperature of 30 °C and the adsorbent dose of 0.1 g L−1, approximately 94.88% of MBD were removed. To find the best-fit isotherm model, the error function equations are applied to the isotherm model findings. Both Tempkin and Freundlich isotherm models could appropriate the equilibrium data, as well as the pseudo 2nd order kinetics model due to high correlation coefficients (R2). Thermodynamic and Freundlich model parameters were assessed and showed that the mechanism of the sorption process occurs by an endothermic and physical process. According to the results of the experiments, S. latifolium is a promising environmentally friendly approach for eliminating MBD from the aqueous solution that is also cost-effective. This technology could be useful in addressing the rising demand for adsorbents employed in environmental protection processes. [ABSTRACT FROM AUTHOR]

Pollution of water resources with various organic and inorganic pollutants is one of the biggest challenges of the present age. These infections seriously threaten human health and the lives of plants and animals. To minimize the mischievous effects of polluted water, technology-based smart treatment methods are necessary for sustainable equipping of drinking water. Application of (AAC-co-AM)-g-MCC hydrogels for the percentage removal of dye Methyl volute MV, from aqueous solutions have been studied. The synthesized (AAC-co-AM)-g-MCC hydrogels was described via FTIR, Thermogravimetric analysis (TGA), and UV-visible spectroscopy. The experiments held out in batch method effect of the factor like the solution of pH, initial concentration dye, and solution of temperature on the removal percentage of dye was studied. Contact time was done in 120 min. The data appear that an amount of 0.08 g (AAC-co-AM)-g-MCC hydrogels showed maximum removal percentage capacity of dye (100 mg L-1). Maximum adsorption of MV dye was attained at pH 6.2. It was further proven the adsorption dye onto (AAC-co-AM)-g-MCC hydrogels followed the isotherm Langmuir while the kinetics studies detect that each adsorption method was pseudo-second-order. The thermodynamic factors like enthalpy (ΔHo), change in free energy (ΔGo), and entropy (ΔSo) were determined, and the values negative of ΔGo indicated that the method of removal was spontaneous at wholly values of temperatures. Further, the values of ΔHo indicated the endothermic nature of the method of removal. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) has recently gained plenty of attention as an effective adsorbent for gold recovery from leaching solutions, primarily due to its larger surface area compared to activated carbon (AC). In this study, the adsorption behavior of gold glycinate complex (Au gly 2 −) on GO surface was investigated using equilibrium isotherm and kinetic studies for the first time. The optimal conditions for adsorption were determined using an experimental design software (DX-13) based on the response surface method (RSM). These conditions were found to be a pH of 10.5, GO dosage of 0.6 g L−1, gold concentration of 6 mg L−1, and contact time of 10 h, resulting in the adsorption percentage of 74.2% and adsorption capacity of 7.4 mg g−1. The equilibrium isotherm studies indicated that the adsorption process adhered to the Freundlich isotherm model. Additionally, the results of the kinetic study revealed that the pseudo-second-order model exhibited a stronger correlation with the experimental data compared to other kinetic models. Surface analysis studies using Fourier transform infrared (FTIR) spectrometer, X-ray diffraction (XRD), and scanning electron microscope with energy dispersive X-ray (SEM-EDX) spectroscopy demonstrated that the remarkable recovery of Au gly 2 − was mainly attributed to the presence of oxygen containing functional groups on the GO surface. • The optimum conditions of Au gly 2 − adsorption on graphene oxide (GO) were found. • Adsorption capacity and adsorption percent were 7.4 mg g−1 and 74.2%, respectively. • The adsorption process followed the Freundlich isotherm and pseudo-second order kinetic model. • Chemical interaction of Au gly 2 − on GO followed a multilayer heterogeneous and reversible adsorption. • Adsorption of Au gly 2 − was related to the porous structure, and the oxygenous functional groups on GO surface. [ABSTRACT FROM AUTHOR]

[Display omitted] • Water adsorption by porcelain stoneware spray-dried powder is investigated. • Porcelain stoneware powder has low hygroscopicity with minor temperature impact. • New approach to estimate diffusion coefficients using sorption kinetics data. • Intragranular pores likely 13% saturated with water in industrial storage conditions. [ABSTRACT FROM AUTHOR]

Batch adsorption experiments were carried out to study the removal of the toxic Methylene Blue Dye (MBD) from synthetic aqueous solutions using the nanoparticles form of Arthrospira platensis NIOF17/003. The adsorption capacity of the adsorbent for MBD was investigated using different amounts of A. platensis nanoparticles at different contact times, temperatures, pH, and MBD initial concentrations in the synthetic aqueous solution. In addition, A. platensis nanoparticles were characterized using Electron Microscopy (SEM), Brunauer–Emmett–Teller (BET), Fourier Transform Infrared (FTIR), and Ultraviolet spectra (UV) techniques. The optimum removal of MBD was found at a concentration of 0.4 g A. platensis nanoparticles. A. platensis nanoparticles remove 93% of MBD in 5 min (under agitation conditions at 150 rpm). The highest adsorption capacity was found by the Langmuir model to be 58.8 mg g−1. It is an endothermic process with spontaneity increasing with temperature. The probable mechanism for the adsorption is chemisorption via surface-active charges in the initial phase, which is followed by physical sorption by occupying pores of A. platensis. MBD adsorption by A. platensis follows pseudo-second-order kinetics. The Freundlich and Langmuir models fit well with the experimental data. The adsorption experiments suggested that the regeneration of the adsorbents was possible for repeated use, especially regarding MBD up to 65.8% after three cycles, which proves it can be easily recycled. In conclusion, the nanoparticles of A. platensis have a significant adsorption potential in the removal of MBD from effluent wastewater.

The dried form of the brown seaweed Sargassum latifolium was tested for its ability to remove toxic Methylene Blue Dye (MBD) ions from aqueous synthetic solutions and industrial wastewater effluents. In a batch adsorption experiment, different initial concentrations of MBD (5, 10, 20, 30, and 40 mg L−1), sorbent dosages (0.025, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5 g L−1), contact time (5, 10, 15, 30, 60, 120 min), pH (3, 5, 8, 10, and 12), and temperature (30, 40, 50, 60 °C) were observed. Dried powder of S. latifolium was characterized before and after adsorption of MBD using different techniques, such as FTIR, SEM, UV visible spectral examination, and BET techniques. The BET surface area suggests the formation of S. latifolium was 111.65 m2 g−1, and the average pore size was 2.19 nm. The obtained results showed that at an MBD concentration of 40 mg L−1, the adsorption was rapid in the first 5, 10, and 15 min of contact time, and an equilibrium was reached in about 60 and 120 min for the adsorption. At the optimum temperature of 30 °C and the adsorbent dose of 0.1 g L−1, approximately 94.88% of MBD were removed. To find the best-fit isotherm model, the error function equations are applied to the isotherm model findings. Both Tempkin and Freundlich isotherm models could appropriate the equilibrium data, as well as the pseudo 2nd order kinetics model due to high correlation coefficients (R2). Thermodynamic and Freundlich model parameters were assessed and showed that the mechanism of the sorption process occurs by an endothermic and physical process. According to the results of the experiments, S. latifolium is a promising environmentally friendly approach for eliminating MBD from the aqueous solution that is also cost-effective. This technology could be useful in addressing the rising demand for adsorbents employed in environmental protection processes.

This study employed simple polystyrene-coated magnetite nanoparticles (PS@MNPs)-assisted batch adsorption process for the removal of two antidepressant active ingredients (amitriptyline HCl and sertraline HCl) from hospital wastewater. Dominant parameters of the adsorption process including pH, adsorbent amount, and contact period were optimized through the univariate approach to enhance the adsorption efficiency. Upon reaching optimum adsorption conditions, equilibrium experiments were performed by spiking the adsorbates in hospital wastewater in the concentration range of 100-2000 μg/L. The concentrations of the adsorbates in the effluent were calculated using the matrix-matching calibration strategy to enhance the accuracy of quantification. A validated switchable solvent-based liquid phase microextraction (SS-LPME) method was employed to enrich the two active pharmaceutical ingredients (APIs) prior to sensitive determination with GC-MS (gas chromatography-mass spectrometry). The equilibrium data were mathematically modeled employing the Langmuir and Freundlich adsorption isotherm models. The isotherm constants were calculated, and the results showed that both the isotherm models fitted well with the experimental data. The efficient and simple batch adsorption strategy reported in this study was successfully employed to remove amitriptyline HCl and sertraline HCl from hospital wastewater at low concentrations., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

In this study, the effectiveness of lala clam (Orbicularia orbiculata) shell, a fishery waste, as an adsorbent for removal of Cd(II), Cu(II) and Pb(II) ions from contaminated water was evaluated by characterization and adsorption studies. The characterization study was performed using Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray (EDX) Spectroscopy and Fourier Transform Infrared (FTIR) Spectroscopy techniques. The effects of solution pH (pH 1.0 to 6.0), adsorbent dosage (0.125 to 0.750 g) and initial adsorbate concentration (10 to 200 mg/L) on adsorption capacity of lala clam shell were studied. The capability of lala clam shell to remove metal ions from aqueous solution was assessed in both single- and mix-metal systems. The adsorption equilibrium data were fitted to Freundlich and Langmuir isotherm models. At an optimum solution pH of 6.0 and initial metal ion concentration of 200 mg/L, the maximum adsorption capacity (Qmax) values of Cd(II), Cu(II) and Pb(II) ions were determined as 66.66, 64.94 and 100.00 mg/g, respectively. The removal performance of lala clam shell (63.80 to 93.79%) for metal ions from battery manufacturing wastewater was comparable to that of three commercial activated carbons derived from olive tree wood (73.01 to 94.83%), coconut shell (68.10 to 95.17%) and bamboo (69.33 to 94.48%), which are commonly used for water treatment in Libya, Malaysia and Indonesia, respectively. The results obtained from this study suggest that lala clam shell exhibits a great potential to be used as an effective alternative to expensive adsorbents for water treatment.

Presence of arsenic in groundwater, eventually in drinking water, has been recognised as a serious community health problem, due to its high toxic nature. Therefore, its removal is highly essential. Chitosan-based adsorbents have been widely used in water treatment in the present scenario due to their abundance and cost-effectiveness. However, there are some problems hindering its practical use, such as low tensile strength and low solubility in acidic mediums. Thus, in this work, to enhance the adsorption capacity of chitosan for the removal of As (V), it has been modified by grafting with monomer HEMA and SSS using gamma radiation. Modified chitosan was characterised by SEM and FTIR spectroscopy. In grafted and ungrafted chitosan, maximum adsorption capacity was found to be (16.8) mg/g and 1.78 (mg/g) using the 0.1 g of adsorbent dose at pH 3–4 in 35 min, and initial As (V) concentration of 60 mg/L. Isotherm study reveals the adsorption process followed by Langmuir isotherm model for both grafted and ungrafted chitosan. Kinetic study suggested that grafted chitosan followed pseudo second order whereas chitosan followed first order kinetics. The thermodynamics indicated that the adsorption process of modified chitosan for As (V) was endothermic and spontaneous in nature. [ABSTRACT FROM AUTHOR]

In this study date pits of two types of date-palm trees (Phoenix Dactylifera L.), in Saudi Arabia were used as bio-sorbents for heavy metals (e.g. lead and copper) from aqueous solutions. Investigation of equilibrium time and the effect of different concentrations of metals were performed. Adsorption capacity of bio-sorbents increases with increasing concentration of metal ions. Maximum adsorption capacity at room temperature of Sukkari date pits was 17.53 mg g-1 and 9.86 mg g-1 for lead and copper ions, respectively. Whereas, Khalas date pits showed maximum adsorption capacity at 14.1 mg g-1 and 7.91 mg g-1 for lead and copper ions, respectively at room temperature. Equilibrium isotherm models, (Langmuir and Freundlich models), were used for analysis of equilibrium experimental results. these models describe the experimental data well. [ABSTRACT FROM AUTHOR]

The study evaluated the effectiveness of an aquatic plant, Canna indica to remove 2,4,6-Trichlorophenol (TCP) from aqueous solution in a hydroponic set-up. The effects of TCP initial concentration (50–250 mg/L) and solution pH (4–9) on TCP biosorption were investigated. The removal efficiency increased with days and initial concentrations. The optimum removal was obtained at pH 4.0. The equilibrium data obtained were analysed by Langmuir, Freundlich, Temkin, Elovich and Dubinin-Radushkevich isotherm models. The equilibrium time was found to be 20 days. The Langmuir and Freundlich model gave the best correlation with the experimental data. According to Langmuir model, the maximum monolayer biosorption capacity of C. indica for TCP was found to be 52.08 mg/g, at 25 ± 2°C. The adsorption was found to follow the pseudo-first-order kinetics. The intraparticle diffusion model revealed that intraparticle diffusion is not the sole rate-limiting step for the biosorption process. Thermodynamic parameter such as standard free energy (ΔGo) was −2537.697 kJ/mol. This showed that the biosorption process was highly spontaneous and proceeded mainly by chemisorption process. C. indica used in this study is eco-friendly, widely available and offers greater potential for wastewater treatment for removal of chlorinated pollutants such as TCP from aqueous solutions. [ABSTRACT FROM AUTHOR]

• VPSA cycle can reduce the feed pressure from ∼18 bar to 6 bar. • H 2 with high purity (>99.99%) and recovery (>92%) can be separated from COG by VPSA. • The effect of vacuum and compression on specific power consumption is comparable. • The partial pressure form LDF mass transfer model is used in mass conservation. • The flow direction of the pressure equalization step affects the mass transfer zone. Hydrogen is a major component of coke oven gas (COG) and can be used in gas-based direct reduction iron processes to help the steel industry achieve the carbon peaking and carbon neutrality goals. However, the high compression power consumption is the main drawback of the current PSA cycle since the COG needs to be compressed from atmospheric pressure to ∼18 bar to achieve a hydrogen production with purity >99.9% and recovery < 85%. Here in this study, we experimentally demonstrate by using a 4-bed 12-step lab-scale VPSA rig filled with activated carbon RB3 and can obtain a hydrogen product with a purity of 99.67% and a recovery of 91.97% at a feed pressure of only 5.17 bar. We then constructed a non-isothermal non-adiabatic VPSA model using our in-house code and validated the model against experimental breakthrough and VPSA cycles. Parametric optimization produced a H 2 product of 99.995% purity and 92.29% recovery at a slightly increased adsorption pressure of 6 bar and a vacuum pressure of 0.02 bar with 10.21 mol.H 2 /kg.ads/hr productivity and 7.09 kJ/mole.H 2 specific power. We also confirmed that light product purge at vacuum pressure can effectively improve the H 2 purity and the gas flow direction of the pressure equalization step has a significant effect on the mass transfer front. Our research presents the success of low-pressure hydrogen production from COG, which will greatly accelerate the transformation of COG utilization and promote the decarbonization of the iron and steel industry. [ABSTRACT FROM AUTHOR]

This article describes how selectively anionic organic molecules could be removed from aqueous medium using naturally available gypsum (GS) adsorbent. Gypsum (CaSO4.2H2O) shows strong interactions with anionic dye molecules while it dos not show any affinity towards cationic dye molecules. We have shown the removal efficiency of gypsum taking chlorazole yellow (anionic dye) and methylene blue (cationic dye) as examples of adsorbates. The GS has been to be even more effective than activated carbon in attaining chlorazole yellow (CY) removal. Three well-known kinetic equations e.g. pseudo-first-order, pseudo-second order and intraparticle diffusion were exploited to interpret the experimental data. Results show best fitting with second order kinetic process with excellent regression coefficient (r2 = 0.99) for the adsorption process. The equilibrium data were analyzed exploiting some adsorption isotherm models. It was apparent that the Freundlich isotherm model superbly fitted for CY dye adsorption process. And the maximum adsorption capacity, Qm, was obtained as 12.85 mg g−1 at room temperature. The negative values of Gibb's free energy change (ΔGo) suggests that the CY dye molecule adsorption process is spontaneous in nature. Moreover, negative enthalpy change (ΔHo) indicates the exothermic nature of the adsorption process. The outcome could be exploited where anionic organic molecules are required to be separated, selectively. [ABSTRACT FROM AUTHOR]

This study focuses on the modification of lightweight expanded clay aggregate (LECA) with sulfuric acid, potassium hydroxide, and sulfuric acid-potassium hydroxide to enhance the removal efficiency of the highly hazardous herbicide (paraquat) from the aqueous solution. The modification results showed that samples activated with sulfuric acid before KOH yielded higher removal efficiency (70.8%) than those activated with acid or base (25.6% and 35.8%, respectively). The paraquat uptake mechanism by LECA was investigated using XRD, XRF, FTIR, FESEM, BET, and zeta potential measurements. Batch adsorption tests were conducted under different conditions using LECA and acid-base-modified LECA. The results indicated the maximum removal efficiency for PQ at 240 min contact time, adsorbent dose of 3.5 g L−1, and pH 9 was achieved with the acid-base treated sample. Experimental data were evaluated with different isothermal, thermodynamic, and kinetic models. The pseudo-second-order model with a correlation coefficient of R2 > 0.99 was congruent with experimental results for LECA and acid-base-activated LECA through kinetic investigations. The highest adsorption capacities for the LECA and acid-base-activated LECA samples, respectively, were 6.12 mg g−1 and 21.23 mg g−1 according to the Langmuir equilibrium isotherm, which offered greater agreement with the experimental results. A negative standard enthalpy change (−21.09 kJ mol−1) and Gibbs free energy change for PQ uptake at 15, 25, and 35 °C indicated an exothermic and spontaneous process. Reusability studies confirmed that the treated adsorbent could successfully remove paraquat even after four regeneration cycles. [Display omitted] • Acid and base treatments of LECA were performed for PQ adsorption. • Acid-base-activated LECA significantly increased PQ removal. • Electrostatic interactions were the predominant uptake mechanism of PQ. • The Langmuir isotherm best described the PQ equilibrium data. • The pseudo-second-order model could be covered more experimental points. [ABSTRACT FROM AUTHOR]

Abstract A comparison of the linear and non-linear regression method in selecting the optimum isotherm among three most commonly used adsorption isotherms (Langmuir, Freundlich, and Redlich–Peterson) was made to the experimental data of fluoride (F) sorption onto Bio-F at a solution temperature of 30 ± 1 °C. The coefficient of correlation ( $$r^{2}$$ r 2 ) was used to select the best theoretical isotherm among the investigated ones. A total of four Langmuir linear equations were discussed and out of which linear form of most popular Langmuir-1 and Langmuir-2 showed the higher coefficient of determination (0.976 and 0.989) as compared to other Langmuir linear equations. Freundlich and Redlich–Peterson isotherms showed a better fit to the experimental data in linear least-square method, while in non-linear method Redlich–Peterson isotherm equations showed the best fit to the tested data set. The present study showed that the non-linear method could be a better way to obtain the isotherm parameters and represent the most suitable isotherm. Redlich–Peterson isotherm was found to be the best representative ( $$r^{2}$$ r 2 = 0.999) for this sorption system. It is also observed that the values of $$\beta$$ β are not close to unity, which means the isotherms are approaching the Freundlich but not the Langmuir isotherm.

In this study, activated carbon biomass was prepared from pistachio hull (PiH-AC). The PiH-AC was used for removal of methylparaben (MP) and propylparaben (PP) from aqueous media. The biomass was fully characterized using Fourier transform-infrared spectroscopy, field emission-scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Brunauer-Emmett-Teller surface morphology. The important parameters including pH of the solution, adsorbent dosage, ionic strength, contact time, initial solution concentration, and temperature were investigated. Furthermore, the process was fitted with adsorption isotherms, kinetics, and thermodynamic models to validate and predict the adsorption nature and mechanism. The Langmuir adsorption isotherm and pseudo-second-order kinetic models were best fitted to the experimental data. Langmuir isotherm was predicted monolayer pattern for selected parabens sorption with appropriate adsorption capacity of 55 and 50 mg g-1 for MP and PP, respectively. The value of free energy (Ea = ~2.45 kJ mol-1) suggests a physisorption mechanism for selected parabens uptake onto the PiH-AC. [ABSTRACT FROM AUTHOR]

The adsorption of Basic Blue 41 (BB41), Methylene Blue (MB) and Basic Red 18 (BR18), three known basic dyes, was studied in shaped mesoporous adsorbent MCM-41. The granules were obtained by extrusion of the powder adsorbent and were analyzed by nitrogen adsorption, SEM–EDS, XRD, mercury porosimetry and helium picnometry. Adsorption equilibrium isotherms, kinetics, and breakthrough curves were performed with the selected adsorbent and dyes. The experimental results indicated that the Sips model better describes the equilibrium than the Langmuir and Freundlich isotherm models. Additionally, the co-adsorption equilibrium of two dyes was well predicted by the extended form of the Sips model. The kinetics results showed that the adsorption of Basic Blue 41 onto the selected adsorbent is faster than with the other studied dyes. The obtained adsorbed equilibrium amounts through the breakthrough curves were 308 mg g−1, 55 mg g−1 and 106 mg g−1 for the Basic Blue 41, Methylene Blue and Basic Red 18 dyes, respectively. The dye is concentrated during regeneration step, since the volume of regenerating solution, eluted during the regeneration, is considerably lower (about two orders of magnitude) when compared with the volume of effluent treated until the breakthrough point. This fact demonstrates the feasibility of a potential adsorption based process to treat dyed effluents, with the shaped MCM-41. [ABSTRACT FROM AUTHOR]

Phosphate, which can cause eutrophication of the aquatic environment, can be effectively removed by an adsorption process using calcium-containing adsorbents. In this study, Ca-carbon foam was prepared by a simple method that entailed addition of Ca during the manufacturing process of carbon foam, and the phosphate removal characteristics of the prepared foam were analyzed using kinetic, equilibrium isotherm, and artificial neural network (ANN) models. The phosphate adsorption capacity decreased with an increase in the solution pH from 3.05 to 6.99. Furthermore, phosphate adsorption increased with increasing time, and the kinetic data were found to be well described by a pseudo-second- order model. The Freundlich isotherm provided the best fit of the equilibrium data, which indicates multilayer adsorption of phosphate on the Ca-carbon foam. The phosphate adsorption capacity as a function of three operational parameters—solution pH, initial phosphate concentration, and time—was well predicted by an ANN model (R² > 0.993), and the optimal ANN for the process of phosphate adsorption on Ca-carbon foam had a 3–20–1 structure with 20 hidden layers. The solution pH was the most influential operational parameter out of all the examined parameters. The results of these analyses are expected to be useful in designing the process of phosphate adsorption from aqueous solutions. [ABSTRACT FROM AUTHOR]

The high concentration of Fe3+ ions present in ammonium phosphate solutions have a significant effect on product quality and product morphology. Herein, hybrid adsorbents fluor(calcium silicate)/activated carbon (FCS/AC) combined with fluor(calcium silicate) (FCS) and activated carbon (AC) were prepared, characterized, and applied in the removal of Fe3+ ions from ammonium phosphate solutions. FCS/AC held both advantages of FCS and AC indicating a significant adsorption for Fe3+ ions. The adsorption kinetics, isotherms and thermodynamics of Fe3+ onto FCS/AC were investigated. The effect of solution pH, initial Fe3+ concentration, temperature and contact time on the adsorption of Fe3+ onto FCS/AC were also investigated. Desorption-resorption experiments of FCS/AC for Fe3+ ions were examined by the batch method using different eluents. The results showed that FCS/AC was an excellent, low cost and reusable adsorbent for the removal of Fe3+ ions from ammonium phosphate solutions, and the adsorption process appeared to follow the pseudo-second-order kinetic model and Langmuir isotherm model with a maximum Fe3+ adsorption of 15.41 mg/g. Various thermodynamic parameters such as △ G 0, △ H 0 and △ S 0 were calculated indicating the feasibility of the process and spontaneous nature of the adsorption. [ABSTRACT FROM AUTHOR]

• Al-substituted hydroxyapatite was grown in-situ on porous wood charcoal (Al-HApC). • Granular composite adsorbent showed remarkable fluoride uptake capacity (105 mg/g). • The adsorption mechanism was identified as chemisorption. • The adsorbent was reused for five cycles without any loss in efficiency. • Fixed-bed column experiment showed 1415 bed volume at breakthrough. In this study, aluminium substituted hydroxyapatite (Al-HAp) was synthesized in-situ on granular commercial wood charcoal at room temperature for fluoride removal from groundwater. Granular size (0.5–3.0 mm) of the carbon particles was selected considering the practical application of the final adsorbent in a packed-bed column filter. The adsorbent was characterized thoroughly. The Al-HAp phase was precipitated inside the pore channel as well as on the surface of highly porous wood charcoal matrix. The adsorbent had surface area of 442 m2/g and pH zpc value was 5. The maximum fluoride adsorption capacity at 303 K was achieved as 105 mg/g which is the highest for any granular adsorbent reported till date for adsorption of fluoride. Batch studies were used to deduce the effective role of pH, temperature and ion selectivity on adsorption efficiency. The reusability of the media was tested upto five cycles after consecutive regeneration with 1 M NaOH. Using the developed media, continuous column run experiments were conducted at different operating conditions, viz., bed volume, flow rate and feed concentration. The maximum number of bed volume was obtained as 1415 for a 30 cm bed height with flow rate 10 L/day and feed concentration of 3 mg/L. A fundamental mass transport model based on pore-diffusion was used to simulate breakthrough behavior in fixed-bed column runs with the synthetic and real contaminated groundwater. The relevant model parameters, namely, fixed bed mass transfer coefficient (k fb), effective pore diffusivity (D p) and the coefficient of axial dispersion (E z) were estimated. [ABSTRACT FROM AUTHOR]

• Adsorption mechanisms of methylene blue onto EDTAD-modified magnetic baker's yeast (EMB) were deeply studied. • EMB showed super-paramagnetic characteristic of nano-Fe 3 O 4 for isolation and recovery and good adsorption capacity of EDTAD for cationic dye. • Specific surface area of EMB was 94.972–499.85 m2/g which was around twice bigger than that of MB. Magnetic baker's yeast (MB) was prepared using glutaraldehyde cross-linking method and chemical modification with ethylenediaminetetraacetic dianhydride (EDTAD). The fabricated EDTAD-modified magnetic baker's yeast (EMB) was then employed to remove methylene blue. Comparative adsorption of methylene blue by EMB and MB was systematically investigated with respect to pH, contact time, initial concentration and reaction temperature. The mechanism of methylene blue adsorption by EMB and MB was investigated by SEM, FTIR and Special surface area using methylene blue method. The results revealed that Fe 3 O 4 nanoparticles were steadily cross-linked/incorporated with baker's yeast biomass and the EDTA was modified on the surface of the magnetic baker's yeast. The equilibrium adsorption data were fitted better by Langmuir isotherm, and the specific surface areas were 42.953–226.07 m2/g for MB and 94.972–499.85 m2/g for EMB, respectively. Kinetic studies suggested that the pseudo-second-order model was suitable to describe the adsorption process. Thermodynamic studies indicated that the adsorption was feasible, spontaneous and endothermic. The recovery efficiencies were above 80% by using 0.1 M HCl. [ABSTRACT FROM AUTHOR]

The potential of raw date pits as a natural, widely available and low-cost agricultural waste has been studied in order to adsorb cationic dyes from an aqueous solution. Date pits were characterized by FTIR, SEM, BET, and XRD analysis. To optimize removal of two industrial dyes, basic red 2 (BR2) and methyl violet (MV), from aqueous solution using date pits, response surface methodology (RSM) is employed. Tests were carried out as per central composite design (CCD) with four input parameters namely contact time, temperature, initial concentration of adsorbate, and pH. Second-order polynomial model better fits experimental data for BR2 and MV and optimum values were then determined. In the optimum conditions, kinetic study was conducted and the pseudo-second-order model was found the best fitted model compared to pseudo-first-order model. Moreover, it was shown that intraparticle diffusion was not the sole controlling step and could be associated with other transfer resistance. On other hand, equilibrium isotherms were obtained for BR2 and MV and their maximum adsorption capacities were 92 and 136 mg g−1 respectively. Two-parameter isotherm models like Langmuir, Temkin, Freundlich, Dubinin–Radushkevich, and Halsay were investigated to fit equilibrium data. Three error functions of residual root mean square error, chi-square statistic, and average relative error were used to comfort us in the selected models, which were actually Dubinin–Radushkevich and Langmuir for BR2 and Frendlich, Temkin, and Halsay for MV. [ABSTRACT FROM AUTHOR]

Abstract Introduction: The Lead causes severe damage to several systems of the body, especially to bony tissues. Until now, several low-cost biosorbents have been studied for removal of heavy metal ions from aqueous solutions. In the present study, carbonized pomegranate peels modified with Fe2+ and Fe3+ ions and then it was investigated for removal of Pb(II) ions from aqueous solution. Materials and methods: the washed granola of pomegranate peel was separately socked with FeCl3 and FeCl2 solutions for 24 h. Then, the granules were carbonized at 400 ºC for 3 h in a programmable furnace in the atmosphere of nitrogen. The adsorption experiments were carried out for two types of iron-modified carbons by batch adsorption using one variable at a time procedures. Results: The optimum conditions were found as contact time 90 min, initial concentration 50 mg/l, and adsorbent dose, 1.00 g/100 ml solution. Maximum removal efficiency was calculated as 84% and 89% for Fe3+ and Fe2+ impregnated pomegranate peel carbons respectively. Conclusion: The iron treatment pomegranate peel carbons modified their surfaces for adsorption of heavy metals. The results showed that chemical modification of the low-cost adsorbents originating from agricultural waste has stood out for metal removal capabilities.

Abstract Introduction: Textile industry is regarded as one of the largest producers of dye and organic compounds, and Methylene Blue is the most commonly used dye material. In the present study, peanut shell powder was used as a low-cost adsorbent for removal of Methylene blue dye from aqueous solutions. Methods: In this experimental study, effect of operating parameters including pH (2-12), reaction time (5-210 min), adsorbent dosage (0.1-1 g/l) and initial dye concentration (10-120 mg/l) were assessed on dye removal from synthetic wastewater. Moreover, the adsorption behavior of dye was evaluated by Freundlich and Langmuir isotherms. Results: Maximum removal efficiency of methylene blue was achieved at optimal pH of 11, reaction time of 75 min, adsorbent dosage of 8 g/l and initial dye concentration of 10 mg/l. With increasing dye concentration from 10 to 100 mg/l, removal efficiency was decreased from 99.5% to 96.46%. The obtained data demonstrated that adsorption process of Methylene blue using peanut shell powder was well fitted with Langmuir isotherms (R2=0.894). Conclusion: Based on the results of the current study, the peanut shell seems to have an appropriate ability in Methylene blue dye removal from aqueous solution, and textile industry wastewater.

Abstract The characterized 1,8-(3,6-dithiaoctyl)-4-polyvinyl benzenesulphonate (dpvbs) resin was used as an effective sorbent for aqueous Hg removal. The adsorbed Hg on dpvbs at the optimum conditions and the synthesized Hg-dpvbs complex were characterized utilizing EDS, XPS, BET and FT-IR. The spectral data for both samples are identical showing that Hg(II) is bonded to dpvbs through sulfur and oxygen atoms. The XPS data indicated that Hg is adsorbed as Hg((NO) 3) 2.The surface morphology of dpvbs before and after sorption processes was studied utilizing SEM and AFM. The thermal stability and thermodynamic parameters were estimated showing an endothermic behavior with less order transition state. Batch adsorption tests were conducted to identify the optimum conditions at which dpvbs have the highest mercury capacity. The resin has the maximum capacity of 435.13 mg g−1 resin (98.95%) and distribution coefficient of 249.36. The adsorption kinetic data fitted best with the pseudo-second-order model. Upon studying the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models, the equilibrium data fitted well with Freundlich isotherm. Relying on the value of E D–R , the mechanism of adsorption process is proposed as physisorption. The modified resin was applied for the removal of metal ions from marine water, utilizing column system and showed high sorption capacity. Graphical abstract Unlabelled Image Highlights • Morphology change upon Hg(II)-dpvbs formation • The versatility of AFM, XPS and SEM to understand the Hg(II)-dpvbs interaction • Optimum pH and Sorption capacity towards Hg(II) on the resin surface • The pseudo-second order model best fits the experimental kinetic data. • Ability of modified resin, dpvbs to remove metal ion from marine water [ABSTRACT FROM AUTHOR]

Codiaeum variegatum stem powder (CVSP) was used as a low cost, readily available and biodegradable sorbent for decontamination of crude oil from aqueous solution. CVSP was characterized by the FTIR, SEM and BET techniques. The physical characterization of the crude oil showed light crude. Equilibrium isotherm of crude oil uptake was analyzed by the Langmuir, Feundlich, Tempkin, Flory-Huggins and Scatchard models. The Langmuir isotherm gave best fit with regression of 0.995 indicating a homogenous CVSP surface involving monolayer sorption of crude oil, supported by the Scatchard model analysis. The maximum monolayer uptake capacity of CVSP for crude oil was established and compared to other reported sorbents. [ABSTRACT FROM AUTHOR]

In this study, different amount of hydroxyapatite (HAP) was embedded into polyethersulfone (PES) matrix to prepare adsorptive mixed matrix membranes (MMMs). All fabricated membranes were characterised based on functional groups, morphology, overall porosity, water content, hydrophilicity and pure water flux. The relationship of equilibrium and kinetics of bovine serum albumin (BSA) adsorption onto fabricated membrane in a batch system was performed. The BSA adsorption equilibrium data is best described by Freundlich isotherm model followed by Langmuir isotherm model. The kinetics of the adsorption is well presented by pseudo-second-order kinetic model and followed by pseudo-first-order kinetic model. Among all membranes, fabricated PES/HAP adsorptive MMM (K4) produced with 60 wt% HAP shows the best characteristic of membrane with higher water content, porosity and hydrophilicity, demonstrating the higher average pure water flux, jw of 29.12 m² l-1 h-1 ± 0.6 m² l-1 h-1, adsorption capacity, qe of 26.54 (g BSA.g membrane-1) and adsorption kinetic rate, k2 of 0.814 (h-1). The reusability of K4 membrane shows the most effective regeneration compare than other membrane. The results suggested that the PES/HAP adsorptive MMM can be effectively applied for the adsorption of BSA from aqueous solution and can offer high potential merit for application in membrane adsorption process. [ABSTRACT FROM AUTHOR]

For the first time the feasibility of using an alkaline wastewater coming from the pulp and paper industry as an activator, partially (50 vol%) replacing commercial sodium hydroxide, in the production of cork-based activated carbons was evaluated. The activated carbons showed the highest value of specific surface area ever reported for cork-based activated carbons (1670 m 2 /g), surpassing several other commercial and waste-based ones. These eco-friendly cork and paper waste-based activated carbons were then evaluated as methylene blue adsorbent materials. The influence of contact time, methylene blue initial concentration and adsorbent amount on the methylene blue removal efficiency by the activated carbons was studied. Extremely fast (>99.9% removal in 5 min) and efficient methylene blue adsorption (uptake of 350 mg/g) by the cork and paper waste-based adsorbents was achieved, which demonstrates the huge potential of these innovative adsorbents. These activated carbons were produced using two unexplored industrial by-products (alkaline wastewater and cork) and, therefore, may be an inexpensive source of activated carbons, which can be used for the effective removal of dyes from wastewaters. Furthermore, despite the very large surface area and high removal efficiency this is not a nano material (being around 30–50 μm in size), its capabilities being due to its unique cork-derived microstructure, and hence it can be handled and removed/filtered much more easily than nanocarbons, and without any associated health or environmental risks. [ABSTRACT FROM AUTHOR]

Cadmium is the toxic metal selected for adsorption in this study and adsorbent of interest was activated carbons prepared from Bauhinia Purpurea leaves as a plant biomass. Batch experimental studies conducted for the given adsorbent imparted that the experimental data were fitted very well with the Freundlich isotherm for the Cadmium adsorption process. The sorption kinetic studies for a given adsorbent indicated that the adsorption tends to follow the pseudo-second order. The suitability of kinetic models followed in the order by Second - order kinetic model > First - order model >Elovich model > Intra-particle diffusion model. The mean adsorption energy E value of Cadmium adsorption was decreased with increasing isothermal temperature (303-323K) from 1.936 to 1.79 kJ/mole. It was observed that the scope of an ordinary free energy credited to physical adsorption and the force of attraction between the adsorbate and adsorbent is very weak, therefore this type of adsorption can be easily reversed by heating or by decreasing the pressure. The characterization of metal-adsorbent interactions before and after adsorption was studied using SEM, FTIR and XRD techniques. FTIR spectrum of raw activated carbon of Bauhinia Purpurea leaves reveals that there were a large number of hydroxyl and carboxyl groups present on the surface of the adsorbent, which possibly reacted with metal ions in aqueous solution. [ABSTRACT FROM AUTHOR]

• Amorphous aluminosilicates have been prepared by coprecipitation at room temperature as low-cost ion exchangers. • Amorphous aluminosilicates show higher cation exchange capacity (CEC) than a synthetic mordenite and a natural zeolite. • The effect of the presence of K+ as competing cation on the ammonium removal efficiency was stronger than that of Na+. • Amorphous aluminosilicates can be regenerated with a KCl solution and reused for the ammonium removal. The efficient removal of ammonium cation, one of the main causes of the eutrophication of water sources, has been achieved by using amorphous aluminosilicates as low-cost ion exchangers. The materials with a Si/Al ratio that varied from 1 to 5 were prepared by the coprecipitation method just by mixing an acidic aluminium sulphate solution with a basic sodium silicate solution, and the products were characterized by XRD, SEM and 27Al MAS NMR spectroscopy. All the amorphous solids presented a higher cation exchange capacity (CEC) than a synthetic mordenite (Si/Al = 9.5) and a natural zeolite (Si/Al = 4.6). The ammonium uptake was investigated as a function of contact time and initial ammonium concentration; additionally, the presence of Na+ and K+ as coexisting cations in the solutions was also evaluated. Langmuir and Freundlich models were applied to describe the data obtained in the ammonium exchange isotherms. The amorphous aluminosilicate with Si/Al = 3 was regenerated with a KCl aqueous solution and was reused 5 times keeping a stable removal efficiency. The reusability of the amorphous aluminosilicate combined with the superior cation exchange capacity manifests the promising use of this type of materials as ion exchangers to remove ammonium cations from wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, the effectiveness of lala clam (Orbicularia orbiculata) shell, a fishery waste, as an adsorbent for removal of Cd(II), Cu(II) and Pb(II) ions from contaminated water was evaluated by characterization and adsorption studies. The characterization study was performed using Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray (EDX) Spectroscopy and Fourier Transform Infrared (FTIR) Spectroscopy techniques. The effects of solution pH (pH 1.0 to 6.0), adsorbent dosage (0.125 to 0.750 g) and initial adsorbate concentration (10 to 200 mg/L) on adsorption capacity of lala clam shell were studied. The capability of lala clam shell to remove metal ions from aqueous solution was assessed in both single- and mix-metal systems. The adsorption equilibrium data were fitted to Freundlich and Langmuir isotherm models. At an optimum solution pH of 6.0 and initial metal ion concentration of 200 mg/L, the maximum adsorption capacity (Qmax) values of Cd(II), Cu(II) and Pb(II) ions were determined as 66.66, 64.94 and 100.00 mg/g, respectively. The removal performance of lala clam shell (63.80 to 93.79%) for metal ions from battery manufacturing wastewater was comparable to that of three commercial activated carbons derived from olive tree wood (73.01 to 94.83%), coconut shell (68.10 to 95.17%) and bamboo (69.33 to 94.48%), which are commonly used for water treatment in Libya, Malaysia and Indonesia, respectively. The results obtained from this study suggest that lala clam shell exhibits a great potential to be used as an effective alternative to expensive adsorbents for water treatment. [ABSTRACT FROM AUTHOR]

In the present work we performed a comparative study on the removal of organic dye by fly ash based geopolymer (FA-G) and metakaolin based geopolymer (M-G). The mineralogical and textural analyses of samples were characterized using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). XRD and SEM confirmed the formation of new geopolymer composites by geopolymerization reaction. The FTIR analysis showed that the adsorbents with good MB adsorption performance can be prepared from rich aluminosilicate materials. The effect of contact time, initial dye concentration, pH of solution and temperature were evaluated by batch test for purification of aqueous solution contaminated by dyestuff. The kinetic adsorption data were analyzed by pseudo-first-order, pseudo-second-order and intraparticle diffusion models. The experimental data were evaluated using the linear forms of the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. The best condition for maximum dye removal was found at high pH. The mechanism of kinetic adsorption by two adsorbents was described by pseudo-second-order model. Adsorption isotherms revealed that the adsorption followed a Langmuir model for adsorbents and the maximum dye adsorption capacity as predicted by Langmuir isotherm was 37.04 mg/g for FA-G and 43.48 mg/g for MK-G. On the whole, the experimental results showed that the innovative adsorbents are suitable for the effective treatment of aqueous solution contaminated with organic dye. [ABSTRACT FROM AUTHOR]

In the present study, the efficacy of razor clam shell to remove Cd(II), Cu(II) and Pb(II) ions from aqueous solutions was investigated. A series of adsorption tests were carried out as a function of solution pH, adsorbent dosage and initial metal concentration. The performance of razor clam shell to sequester Cd(II), Cu(II) and Pb(II) from single- and multi-metal adsorption systems was also assessed in details. The adsorption of three metal ions studied was more favourable at low acidic pH media. The Freundlich and Langmuir isotherm models were employed to correlate the adsorption equilibrium data. Based on isotherm data, the adsorption affinity of metal ions towards razor clam shell was in the order of Pb(II) > Cd(II) > Cu(II), with maximum adsorption capacities of 357 mg/g, 103 mg/g and 98 mg/g for Pb(II), Cd(II) and Cu(II) ions, respectively. In addition, the dimensionless separation factor (RL) values indicate the adsorption of Cd(II), Cu(II) and Pb(II) onto razor clam shell was favourable. The adsorption efficiency of the proposed adsorbent was compared with olive tree derived activated carbon, a commercial adsorbent for water treatment in Libya. Fourier Transform Infrared (FTIR) Spectrometer, Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX) Spectrometer were used to characterise the physicochemical properties of razor clam shell as well as to elucidate adsorption mechanisms involved. Overall, results from this study highlight the feasibility of razor clam shell, a fishery waste based material, as an alternative low-cost adsorbent for remediation of polluted water. [ABSTRACT FROM AUTHOR]

The wastes of Myoporum laetum and Livistona chinensis leaves were utilized for removal of malachite green dye (MG) from solution. The highest removal for dye was observed with M. laetum biomass at pH: 6, temperature: 35 °C, biomass dose: 0.3 g L-1 and contact time: 120 min. The different concentrations of MG (5-35%) were highly removed by M. laetum (99.28% to 79.31%, respectively) as compared with L. chinensis (95.48-69.67%, respectively) at the optimum conditions. The sorption data were represented by Langmuir, Freundlich and Temkin isotherms. Adsorption was established well with isotherms of Langmuir and Freundlich. The study of thermodynamic suggested that the adsorption reaction was endothermic and the sorption of dye onto the biomass proceed in the forward direction and greatly promising process. The removal of dye was characterized by FT-IR analyses and the results confirmed that the groups responsible for the process of dye binding were hydroxyl or amino, and carboxylate or amide. The M. laetum cell wall showed a great porosity which permits the passage of dye molecules. The M. laetum biomass was more efficient than that of L. chinensis. The efficiency of the plant waste for a decolorizing solution containing dye, their abundance in nature and less processing requirements may lead to the emergence of low-cost adsorbents. [ABSTRACT FROM AUTHOR]

The removal of Pb2+, Cd2+, and Hg2+, which act as endocrine disruptors, from aqueous solutions was performed using a NaP1-type zeolite synthesized from a hazardous aluminum waste. The effects of parameters such as pH, contact time, adsorbent dose, initial cation concentration, and coexisting cations on the adsorption efficiency and capacity of the adsorbent were evaluated. Single-cation adsorption was found to be a fast process well described by the pseudo-second-order kinetic model. Equilibrium was reached in the first 15 min achieving high removal efficiencies: 98.9%, 93.3%, and 99.3% for Pb2+, Cd2+, and Hg2+, respectively. The removal of the metal cations could occur via a homogeneous and physical adsorption process that was satisfactorily described by the Sips isotherm. The maximum adsorption capacities, obtained from the Sips isotherm model, were 245.75, 4.43, and 0.22 mg/g for Pb2+, Cd2+, and Hg2+, respectively. In multi-cation adsorption, the zeolite presented the greatest affinity for Pb2+ (due to its smallest cationic size) compared with Cd2+ and Hg2+. The Pb2+ removal efficiency remained practically constant in presence of Hg2+ and Cd2+, reaching efficiencies near 100% at very low contact times (<5 min). Thus, this zeolite could become an alternative adsorbent to eliminate heavy metals from waters. A synergic effect on the environmental protection could be achieved: the end-of-waste condition of a hazardous waste as well as the water decontamination. [ABSTRACT FROM AUTHOR]

Background and purpose: Dyes are one of the main pollutants in the various industrial wastewaters. Therefore, the aim of this study was to assess the biosorption of acid red 18 dyes from aqueous solutions by brown macroalgae biomass “Sargassum glaucescens.” Materials and Methods: This research was a lab study. S. glaucescens was used as an adsorbent to remove acid red 18. The effect of various parameters such as pH, initial dyes concentration, adsorbent dose and equilibrium contact time were evaluated in batch adsorption. The dye concentration was measured in the wavelength of 506 nm by spectrophotometer. Results: The results showed that the equilibrium time of biosorption was 120 min. Increasing of contact time and adsorbent dose and initial dye concentration can lead to increasing of the removal efficiency. The maximum adsorption capacity of the dye was at pH: 6 respectively. It was found that the data fitted to Freundlich better than Langmuir isotherms of adsorption model. Conclusion: The S. glaucescens biomass had a satisfactory quality in dye adsorption. It can be used as an effective, inexpensive adsorbents for the dye adsorption from textile wastewater or similar industries.

The application of microwave activated Acacia nilotica leaves (MVM) and chemically activated A. nilotica leaves (CVM) for the removal of crystal violet (CV) from aqueous solution was studied in a batch system. Equilibrium sorption isotherms and kinetics were investigated. The applicability of the Langmuir model for CV onto CVM and MVM was proved by the high correlation coefficient and non-linear regression such as, residual root mean square error (RMSE), chi-square (χ2), sum of the square of the errors (ERRSQ), composite functional error (HYBRD), derivative of Marquardt’s percent standard deviation (MPSD), average relative error (ARE), sum of absolute error (EABS) and average percentage error (APE). The adsorption of CV onto CVM and MVM follows pseudo-second-order kinetic model with intraparticle diffusion is one of the rate-limiting steps. The adsorption capacity of MVM is greater than CVM. The preparation of MVM is agreeing with the principles of green chemistry. Therefore, the eco friendly adsorbent MVM is expected to be the environmentally and the economically feasible adsorbent for the removal of CV from aqueous solution.

The use of cheap and eco friendly adsorbents prepared from freely and abundantly available Acacia nilotica leaves have been investigated by batch methods. Microwave treated A. nilotica leaves (MVM) are more effective than chemically treated A. nilotica leaves (CVM) for the removal of rhodamine B (RH B) from aqueous solution. The effect of initial pH, contact time and initial dye concentration of RH B onto CVM and MVM has been investigated. The applicability of the linear form of Langmuir model to CVM and MVM was proved by the high correlation coefficients R2 = 0.9413 and 0.9681 for RH B adsorption. The R2 values were greater than 0.994 for all RH B concentrations, which indicates the applicability of the pseudo-second-order kinetic model. The recycling ability of MVM is greater than CVM. The preparation of MVM does not require an additional chemical treatment step and it attains rapid equilibrium. Hence it is agreeing with the principles of green chemistry and less time is required to possess high adsorption of RH B. Therefore, the eco friendly adsorbent MVM is expected to be environmentally and economically feasible for the removal of RH B from aqueous solutions.

The present study investigates the possibility of using low cost agriculture waste as doum-palm seed coat for the removal of nickel ions from aqueous solutions. Two activated carbons had been prepared from raw doum-palm seed coat (DACI and DACII); as well, the raw material was used as an adsorbent (RD). Batch adsorption experiments were performed as a function of pH of solution, initial nickel ions concentration, dose of adsorbent and contact time. Adsorption data were modeled using Langmuir, Freundlich, Temkin and D–R Models. Different error analysis conforms that the isotherm data followed Freundlich models for all adsorbents. Adsorption kinetic data were tested using pseudo-first order, pseudo-second order and Elovich model. Adsorption mechanism was investigated using the intra-particle diffusion model. Diffusion coefficients were calculated using the film and intraparticle diffusion models. Kinetic studies showed that the adsorption of Ni2+ ions onto RD, DACI and DACII followed pseudo-second order kinetic model, and indicates that the intra-particle diffusion controls the rate of adsorption but it is not the rate limiting step.