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In this work, locally available tea wastes were used as precursors for the development of cost-effective bio-sorbent materials for heavy metal removal from wastewater. Chemical and thermal treatments to prepare magnetic/non-magnetic tea waste-based adsorbents were discussed and correlated their properties with corresponding Cr(VI) adsorption capacity. These bio-sorbents were thoroughly characterized by FT-IR, PXRD, N2 adsorption-desorption surface area techniques and Cr adsorption performance was investigated in batch reactor under different conditions such as adsorbent dosage, initial Cr concentration, solution pH and contact time. Careful bleaching steps, incorporation of magnetic iron nanoparticles and judicious temperature treatments of tea wastes resulted in high performing biosorbents with a complete removal of Cr at a dosage of 0.25 g/mL of the solution. Cr adsorption on these tea waste-based bio-sorbents were found to be fitting to a pseudo 2nd order kinetics.

Application of Pistacia atlantica Leaves Powder as Natural Material To Remove Nitrate and Phosphate Ions From Domestic Wastewater by Characterization, Bio-removal, and Phytotoxicity StudiesObaida Alhajali1* , Adnan Ali-Nizam1 , Rasha Almostafa2 1Damascus University, Department of Plant Biology, Damascus, Syria.2International University for Science and Technology, Department of General and Analytical Chemistry, Syria. Abstract: Description of Pistacia leaves powder using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Energy-dispersive X-ray spectroscopy (EDX), specific surface area according to nitrogen adsorption (SBET) and methylene Blue (MB), and point of zero charge determination (pHpzc). A series of batch adsorption tests were conducted to study effect of various factors (plant powders dose, contact time, temperature, pH) on the percentage of nitrate and phosphate removal from domestic wastewater. The adsorption kinetics, regeneration ability test of plant powder, and phytotoxicity tests for treated water and spent powder on germination were studied. Results of SBET analysis showed that Pistacia leaves powders have a low surface area and microscopic pores, SEM images revealed rough surfaces with uneven cavities, EDX analysis showed that there are high percentages of carbon and oxygen, good percentages for nitrogen, and few percentages of potassium, calcium, magnesium, phosphorous, sulfur and chlorine, and FTIR analysis showed that there are more than five distinct absorption peaks. The maximum value of nitrate and phosphate removal was 76.47% and 52.20%, respectively, at powder dose of 2 g/L, temperature 25 °C, and pH 5, and the percentage of nitrate and phosphate removal increased with increasing contact time until equilibrium was reached after 120 min for nitrate and 180 min for phosphate, and It was found that adsorption of ions follows kinetics of reaction from pseudo-second-order model, and powders can be Regeneration and used for two successive cycles with a slight decrease in removal efficiency. Germination tests on Lepidium sativum indicate no phytotoxicity. That is, Pistacia leaves powder is one of the natural products that are effective in removing nitrate and phosphate from domestic wastewater.

In this study, the Response Surface Method statistically optimized Pb(II) adsorption on activated carbon prepared using corn husk. The full central composite design was the statistical method selected for optimization using adsorption capacity as a response factor. The quadratic model best explained the process. Adsorption parameters optimized were solution pH, contact time, temperature, and adsorbent dose. The respective optimum values were 4.5, 64 min, 50°C, and 0.4 g L-1. Adsorption isotherm and kinetics studies evaluated the data obtained at different temperatures using different isotherm and kinetics models. The non-linear curve fitting method determined the model with the best fit. Freundlich’s model best accommodated the isotherm data, whereas the pseudo-second-order kinetic model best modeled the kinetics data. Weber-Morris intraparticle diffusion model revealed the existence of multiple rate-controlling processes. The activation energy for the adsorption of Pb(II) ions was 30.17 kJ mol-1. The thermodynamics studies showed that the process was an entropy-driven endothermic process. Gibb’s free energy (ΔG) values were negative at the studied temperatures, and the spontaneity increased with the increase in temperature. The enthalpy (ΔH) and entropy change (ΔS) was 43.78 kJ mol-1 and 154.2 J mol K-1. The study concluded that the statistical method simplified the optimization of the adsorption process and produced an efficient adsorbent from corn husk.

The aim of the present study was to assess the adsorption potential of a natural adsorbent Oxalis pes-caprae L. for the removal of azo-dye solophenyl red 3BL (SR 3BL) from textile effluents. The adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The effect of various parameters on the efficiency of the adsorption was studied. The optimum was found with the contact time of 35 minutes, pH of 6, and temperature of 25 °C. The equilibrium experimental data were fitted with the Langmuir, Freundlich, and Temkin models. Experimental data were well described with the Langmuir isotherm indicating monolayer adsorption. Pseudo-first-order, pseudo-second-order, and Elovich kinetic models were used to evaluate the adsorption kinetics. The adsorption kinetics was found to follow closely the pseudo-first-order kinetic model. Thermodynamics studies revealed that the adsorption process was spontaneous and exothermic. This work is licensed under a Creative Commons Attribution 4.0 International License.

The fluorine content of groundwater exceeds the standard in most areas of China. In this study, the self-made mesoporous carbon electrode combined with the ion exchange membrane was used to form a ...

Aims The adsorption of lead ions from aqueous solution by macroporous Ca-alginate-lignin (MCAL) beads immobilized with Clostridium tyrobutyricum and free strains was evaluated. Methods and Results The effects of different factors including pH, adsorption time, adsorbent dosage and initial concentration of lead ions were explored. Different characterization methods were used to evaluate the adsorption process of lead ions. Meanwhile, the adsorption kinetics models and adsorption isotherm models were applied. The fitting results showed that the adsorption behaviour of C. tyrobutyricum immobilized in MCAL beads and free strains was better described by the pseudo-second-order kinetic model and the adsorption process followed the Langmuir isotherm model. The maximum biosorption of lead ions by C. tyrobutyricum immobilized in MCAL beads and free strains was 144.9 and 106.4 mg/g respectively. Conclusions The C. tyrobutyricum immobilized in MCAL beads proved to be practicable and had better adsorption effects on lead ions compared with the free strains. Significance and Impact of the Study The paper demonstrated a new insight and strategy for the effective treatment of lead ions from aqueous solutions by the novel function of C. tyrobutyricum.

The aim of this study was to develop an adsorbent from coffee husk, residue from the coffee industry by different activation methods and to evaluate its application in the treatment of effluent containing synthetic Ponceau 4R dye. The activations were with phosphoric acid and zinc chloride, then the samples were characterized in terms of physical and chemical composition, structure and morphology, thermal behavior and kinetic and thermodynamic study. Regarding the characterization of the material, the activation with phosphoric acid showed porous morphology and a high surface area (429.7 m2 g-1) and with the kinetic study it was possible to obtain an equilibrium time of 60 min and dispersion according to Elovich kinetics (R2 = 0.96 and RMSE < 0.24). According to the experimental design, the adsorptive capacity can be evaluated with the significant result (qe = 19.87 mg g-1) under the conditions of 90 min of the adsorption process and at the concentration of 2 g L-1 of adsorbent. In relation to the equilibrium study the Langmuir model fit the data with coefficient of determination of R2 = 0.84. Finally, the Ponceau 4R dye adsorption process using coffee husks as an activated carbon was thermodynamically favorable through the negative Gibbs free energy and positive entropy (+0.022 kJ mol-1 K-1). Therefore, the use of coffee husk as activated carbon proved to be a favorable material for Ponceau 4R dye adsorption.

In this article, triton X-100 (TX-100) adsorption was evaluated by using of graphene oxide-saponin (GO-SA) nanocomposite as an adsorbent. GO was synthesized by the Hummer method and then modified by saponin to prepare GO-SA nanocomposite. The characteristics of GO-SA adsorbent were performed by the scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform-infrared spectrophotometry (FTIR), X-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET). The response surface methodology (RSM) using Design–Expert software and one factor at a time method (OFAT) were applied for optimization of pH of sample solution, amounts of adsorbent and contact time. Kinetic models are scrutinized and the outcomes depict the adsorption of TX-100 onto the GO-SA nanocomposite followed by the pseudo-first-order kinetic model. Also, to evaluate the adsorption mechanism, Dubinin–Radushkevich (D-R), Langmuir, Temkin and Freundlich were appraised and the outcomes demonstrate that the adsorption of TX-100 governed by the Langmuir isotherm with a maximum adsorption capacity of 179 mg g−g. Finally, the proposed adsorbent was successfully applied for the removal of TX-100 in different water samples.

Cashmere is byword for soft, luxury, and expensive stylish clothes. Objective and quantitative methods to identify and possibly quantify recycled cashmere are crucial to discourage adulteration of high-quality virgin cashmere with cheaper recycled fibers. Available analytical methods for the identification of recycled and virgin fibers are currently confined to subjective assays. This work investigates objective and reliable methodologies to quantify the amount of recycled cashmere in blend with virgin one, based on the different dye absorption capacity of recycled and virgin fibers. Pure virgin and recycled cashmere fibers were stained with different amounts of C.I. Direct Red 7 in different conditions, and the exhaust dyebaths were analyzed by UV-visible Spectroscopy in order to quantify the residual unabsorbed dye. Then, the method was applied to blends of different proportions of virgin and recycled cashmere with a correlation of R2 = 0.95.

A N, S, P-codoped and oxidized porous carbon (CS－COOH) was prepared by carbonization of poly(cyclotriphosphazene-co-4,4’-sulfonyldiphenol), followed by KOH activation and oxidation with HNO3. The CS－COOH was used as an adsorbent for U(VI) in aqueous solutions. TEM, SEM, XPS and FTIR were used to characterize the microstructures of CS－COOH before and after adsorption. Results indicate that there is an optimal pH value of 6 for U(VI) adsorption. The adsorption kinetics and isotherm are fitted well by the pseudo-second-order model and the Langmuir model, respectively. The maximum adsorption capacity determined by the Langmuir model at 298 K and a pH value of 6 is 402.9 mg g−1. The CS－COOH has an excellent reusability with a 70% capacity retention of the original value after five adsorption-desorption cycles. The high U(VI) adsorption capacity is mainly attributed to the carboxyl, and P ans S groups by the formation of the UO22+(COO−)2 complex, U－O－P and U－O－S bonds.

This paper focuses on the removal of methylene blue by adsorption using a mixture of titaniferous sand and attapulgite. The different adsorbents were characterized by X-ray fluorescence spectroscopy and their different parameters such as pH, zero charge potential, and specific surface area were determined. The experiments performed were optimized and modeled by a full 2-level and 4-factor design. The four factors are the ratio of titaniferous sand and attapulgite, the concentration of methylene blue, pH, and time. These vary from 4 to 19, 20 to 100 mg/L, 2 to 9, and 30 to 150 min respectively. The study of the effects of the different factors showed that the effect of methylene blue concentration and pH significantly influence the adsorption capacity and removal efficiency of the dye. The optimum parameters (adsorbent ratio, adsorbate concentration, pH and time) obtained for the adsorption capacity through the desirability function are: 19, 100mg/L, 9 and 150min. Those obtained for the yield are: 4, 100mg/L, 9, 150min. The pseudo second order adsorption kinetics gave an equilibrium adsorption capacity qe (calculated) = 7.6863 mg/g which is almost equal to that obtained experimentally qe (exp) = 7.3562 mg/g. This shows that the pseudo second order kinetic model is the adequate mathematical model to describe the methylene blue adsorption phenomenon on the mixture of titaniferous sand and attapulgite. The thermodynamic study showed that the methylene blue adsorption reaction is exothermic, non-spontaneous, and the degree of disorder of the particles at the adsorbing surface decreases.

The efficiency of surface modified nanoscale zerovalent iron (nZVI) composite by cashew nut shell (CNS) was tested for the removal of cadmium ions from the aqueous solutions. 2 g/l CNS-nZVI was efficient for 98% removal. The adsorption capacity was 35.58 mg/g. The Freundlich isotherm (R2 = 0.9769) and the pseudo-second order adsorption kinetics data fitted well. This proved CNS-nZVI has a high removal efficiency for Cd(II) from aqueous solutions.

Model of second-order (SO) adsorption kinetics from solutions was described and verified for the adsorption of phenol/lead (II) on samples of natural coal and activated carbon. The model was compar...

Removal of color from dye-bearing water has been a bothering task from the health point of view and in the aesthetic sense as well. Finding out the effectiveness of Remazole Red RGB dye removal is the aim of the present work using banana stem, an agricultural waste, as an activated carbon. The preparation of the banana stem activated carbon was done in the laboratory by carbonization followed by activation. To assess the impact of varied exploratory variables such as pH of adsorbate, contact time, initial dye concentration and dosage of adsorbent on the removal of Remazole Red RGB dye from aqueous solution adopting batch studies were performed. The Freundlich and Langmuir isotherm models were used to predict the adsorption capacity of adsorbent at equilibrium conditions, the kinetic parameters were also determined. The concentration of dye remaining in the system was measured using a UV visible spectrometer. The batch test resulted in the removal of the maximum of 87% of dye when the dye concentration was 2 mg/L, at an adsorbent dose of 0.5 gm/L and dye pH 4 in 35 minutes. It is established from the studies that the equilibrium data suited excellently both Freundlich and Langmuir isotherms. The maximum adsorption capacity of 14.28 mg/L was established from the Langmuir isotherm model. To state the sorption kinetics, pseudo-first-order and pseudo-second-order kinetic models were evaluated. The intraparticle diffusion model was checked for the adsorption data and it was observed that intraparticle diffusion is not the only rate-limiting step. The regression analysis results indicated that the linear regression model gave the best results. The above detection exhibits that banana stems can be used productively for the removal of color from dye-containing wastewater.

In this paper, porphyrin-based cationic conjugated network (PCCN) nanosheets were synthesized, and its adsorption for TcO4−/ReO4− was investigated. This material was stacked with AB dislocation, with an aperture of 1.2 nm. The Re(VII)/Tc(VII) adsorption kinetics of PCCN is extremely fast, and the adsorption capacity is relatively large, the selective order is ReO4− > NO3− > Cl−. XPS and DFT revealed that the exchange of Cl− on PCCN with ReO4−, while the hydrophobic pore of PCCN are the keys to improve adsorption selectivity. It could be used to remove Tc from groundwater around nuclear facilities.

The use of natural dyes for the dyeing of naturally-derived fibres is of economic and cultural importance in many countries and there is thus ongoing research interest in this area. In the current ...

Discharges from industrial and agricultural processes into water bodies can result in the accumulation of heavy metals such as Cu(II) in the sediment via various physical and chemical interactions. While there are many studies of the adsorption of heavy metals by sediment, few have considered the effects of hydrodynamic conditions. Here, the adsorption of Cu(II) by sediments under different hydrodynamic conditions was studied using a particle entrainment simulator. The sediment samples were obtained from the Poyang Lake basin in China. Models describing pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion kinetics and the Langmuir, Freundlich, Temkin and Dubin Radushkevich adsorption isotherms were used to evaluate the adsorption of Cu(II) by the sediments under different hydrodynamic conditions. The results showed that adsorption equilibrium for Cu(II) by the sediment was attained within 4 hours and increased with increasing shear stress; the kinetics were consistent with pseudo-second-order and Elovich models, indicating that chemical processes were involved in adsorption; the adsorption isotherms could be described by the Langmuir and Freundlich models. Changes in the sediment shear stress had little effect on the maximum adsorption capacity and values ranged from 0.9425 to 1.0634 mg/g. The results indicated that the adsorption sites for Cu(II) in soil were heterogeneous.

In the present study, the algae Undaria pinnatífida has been investigated as a biological adsorbent for the elimination of pollutants from surface waters, specifically heavy metals. Operational parameters were optimized in batch phytoremediation experiments. Adsorption equilibrium isotherm models were also investigated and adsorption kinetics were evaluated. Maximum adsorption capacities were observed at 0.008 mg / L at 0.064 mg / L of Cd and for the second sample the adsorption capacity was calculated at 0.007 mg / L at 0.055 mg / L of Cd both in a time of 24 hours, together With removal efficiencies, they reached 72% and 92.7% for the remediation of the Rio Grande water, respectively. These results are important in the development of zero-cost, algal-based pollutant removal technology in water treatment. En el presente estudio, se ha investigado la algas Undaria pinnatífida, como adsorbente biológico para la eliminación de contaminantes de aguas superficiales, específicamente metales pesados. Los parámetros operativos se optimizaron en experimentos de fitorremediación por lotes. También se investigaron los modelos de isoterma de equilibrio de adsorción y se evaluó la cinética de adsorción. Se observaron capacidades máximas de adsorción en 0.008 mg/L a 0.064 mg / L de Cd y para la segunda muestra la capacidad de adsorción se calculó en 0.007 mg/L a 0.055 mg / L de Cd ambas en un tiempo de 24 horas, junto con las eficiencias de remoción se alcanzaron al 72% y 92.7% para la remediación del agua del río grande, respectivamente. Estos resultados son importantes en el desarrollo de tecnología de eliminación de contaminantes de costo cero basada en algas en el tratamiento de aguas.

Thousands of anthropogenic materials (e.g., micropollutants, MPs) are discharged to surface and groundwaters daily and their wide distribution potentially threatens ecological and human health. Granular activated carbon (GAC) is a widely used adsorbent to remove MPs, but with several deficiencies such as slow adsorption kinetics and hindered performance by natural organic macromolecules (NOM). Here, we detail the synthesis of a novel adsorbent, three-dimensional (3D), stacking-resistant, crumpled graphene oxide balls (CGBs) and their adsorbent properties by using eight persistent MPs under relevant environmental conditions. CGBs displayed 4–8 times greater adsorption capacity than GAC for seven of the eight MPs on a surface area equivalent basis. Kinetic experiments show that seven of eight MPs in a mixture reach >90 % removal efficiency after 15 min contact time (compared to 5–10 % removal of GAC). CGB adsorption performance was also tested as a function of varying NOM concentration, with other realistic environmental conditions of pH, ionic strength, water hardness, and alkalinity, to demonstrate that CGB adsorption of MPs is not adversely affected by NOM even at high concentrations and is stable over a range of field conditions. These findings demonstrate that CGBs are potentially a powerful adsorbent for micropollutant removal in complex aqueous environments.

The adsorption of locust bean gum (LBG) onto Northern Bleached Softwood Kraft (NBSK) pulp improved paper tensile and burst strength and lowered refining energy by strengthening inter-fibre bonding. Adsorption kinetics and isotherms were investigated to develop a fundamental understanding of the adsorption mechanism. The adsorption rate followed pseudo-second-order kinetics and the activation energy was 99.34 kJ·mol−1, suggesting chemisorption. The adsorption rate constant increased rapidly with temperature from 25 to 45 °C (k = 1.93 to 24.03 g·mg−1·min−1), but the amount adsorbed at equilibrium decreased (qe = 1.91 to 0.48 mg·g−1 o.d. fibre). LBG adsorption to NBSK at 25 °C was consistent with the Langmuir adsorption model for LBG n = 5.00, and the equilibrium constant Kf = 2.57 mg·g−1·(mg·L−1)−1/n at 25 °C. Favorable adsorption conditions for negatively charged LBG were identified: 25 °C for 10 min, low dosage level ( 150 r.p.m.), acidic or neutral conditions (pH 2–7) without salt addition. Graphic abstract

Nickel hydroxide (Ni(OH)2 ) is a promising electrocatalyst for the 5-hydroxymethylfurfural oxidation reaction (HMFOR) and the dehydronated intermediates Ni(OH)O species are proved to be active sites for HMFOR. In this study, Ni(OH)2 is modified by platinum to adjust the electronic structure and the current density of HMFOR improves 8.2 times at the Pt/Ni(OH)2 electrode compared with that on Ni(OH)2 electrode. Operando methods reveal that the introduction of Pt optimized the redox property of Ni(OH)2 and accelerate the formation of Ni(OH)O during the catalytic process. Theoretical studies demonstrate that the enhanced Ni(OH)O formation kinetics originates from the reduced dehydrogenation energy of Ni(OH)2 . The product analysis and transition state simulation prove that the Pt also reduces adsorption energy of HMF with optimized adsorption behavior as Pt can act as the adsorption site of HMF. Overall, this work here provides a strategy to design an efficient and universal nickel-based catalyst for HMF electro-oxidation, which can also be extended to other Ni-based catalysts such as Ni(HCO3 )2 and NiO.

Recent studies on the removal of pollutants via adsorption include the use of carbon-based adsorbents, due to their high porosity and large surface area; however, such materials lack photoactive properties. This study evaluates the synergistic effect of integrated mesoporous carbon xerogel (derived from resorcinol formaldehyde) and titanium dioxide (TiO2) for combined adsorption and photodegradation application. The complex formed between carbon xerogel and TiO2 phase was investigated through FTIR, proving the presence of a Ti-O–C chemical linkage. The physicochemical properties of the synthesised adsorbent–photocatalyst were probed using FESEM, BET analysis and UV–Vis analysis. The kinetics, equilibrium adsorption, effect of pH, and effect of adsorbent dosage were investigated. The expansion of the absorbance range to the visible range was verified, and the corresponding band gap evaluated. These properties enabled a visible light response when the system was exposed to visible light post adsorption. Hence, an assistive adsorption–photodegradation phenomenon was successfully executed. The adsorption performance exhibited 85% dye degradation which improved to 99% following photodegradation. Further experiments showed the reduction of microorganisms under visible light, where no microbial colonies were observed after treatment, indicating the potential application of these composite materials.

This work explains a novel method of producing activated carbon using laser treatment. Acrylic coated glass samples were developed by padding a glass non-woven sheet in 30% acrylic fibre solution (PAN solution) from waste acrylic bathmats. Samples were then dried and cured at different temperatures. After curing, stabilisation was performed at 230 °C with a heating rate of 50 °C hr-1. Infrared laser irradiation was performed on the stabilised web using a commercial pulsed infrared laser for carbonisation. The resultant acrylic glass carbon composite (AGCC) was characterised with the help of x-ray diffraction analysis, energy dispersive w-ray, and a scanning electron microscope to determine the increase in crystallinity as well as the percentage of carbon and surface roughness of the carbon glass composites. The adsorption capacity of the activated carbon (AC) glass composite prepared was determined by changing process inputs like the concentration of dye, the amount of AC glass composite, the agitation speed and pH. The results were analysed through different adsorption isotherms. It was established that the Freundlich model can more effectively describe results due to the development of heterogeneous surface characteristics. The kinetics of adsorption were studied using first order and second order models.

The design and preparation of multifunctional adsorbent for practical wastewater treatment is still an enormous challenge. To remove multiple metal ions from wastewater, we developed a broad-spectrum metal ions trap named UIO-67-EDTA by incorporation of ethylenediaminetetraacetic acid into robust UIO-67. The adsorption experiments for 15 kinds of heavy metal ions including hard acid (Mn2+, Ba2+, Al3+, Cr3+, Fe3+), borderline acid (Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Sn2+, Bi2+), soft acid (Ag+, Cd2+, Hg2+), and two kinds of dissolved minerals (Mg2+, Ca2+) show that the trap is very effective both in batch adsorption processes and breakthrough processes. At a pH value of 4.0, the removal efficiency for all metal ions was over 98% within 10 min, and the maximum static adsorption capacity for the representative metal ions Cr3+, Hg2+and Pb2+ was up to 416.67, 256.41, and 312.15 mg g−1, respectively. The adsorption kinetics fitted well with the pseudo-second-order model, indicating that the chemical adsorption was the rate-determining step in the adsorption process. Meanwhile, the material showed high stability and recyclability, the removal efficiency for the three representative metals was still maintained over 93% after five consecutive adsorption cycles. HIGHLIGHTS Fabrication of a broad-spectrum heavy metal ion trap possessing strong chelating groups with high-density active binding sites; Serving as an extremely efficient adsorbent for multifarious and complex metal ions purification; High stability together with recyclability offering a potential possibility for practical applications.

Selenium is one of the necessary nutrients for the growth and development of animals and humans. Improving the activation of selenium in soil is an important way to increase the selenium content in...

In this study, we report the adsorption process of Congo Red (CR) dye by calcined Layered Double Hydroxide (ZAC) at 550°C. The urea hydrolysis method was applied to produce highly crystalline Zn2Al-LDH. Samples characterisation was carried out by X-ray diffraction (XRD), Thermogravimetric/differential thermal analysis (TG/DTA), and Fourier transform infrared spectroscopy (FTIR). The results show that the adsorption of CR on calcined ZnAl-LDH was accompanied by the reconstruction of the layered structure. The ZAC showed higher adsorption efficiency versus other adsorbent under investigation and optimum conditions of contact time, adsorbent dose, pH and temperature were found to be 50 min, 0.02 g, 7 and 318 K, respectively. Isotherm studies show that the Langmuir isotherm model was appropriate to describe the CR adsorption data compared with Freundlich and Temkin isotherm models, with a higher correlation coefficient (R2 > 0.99) and maximum adsorption capacity of 406.5 mg/g. The thermodynamic parameters revealed that the adsorption process was spontaneous, endothermic, and governed by chemisorption. To further facilitate the recovery process in CR adsorption, we test the feasibility of applying ZnAl-LDH and its calcined product at 550°C entrapped in alginate beads. Experimental results indicate that alginate-coated ZAC beads, which exhibited remarkable adsorption performance, were more stable and require less effort to pull and separate than the alginate/ZnAl-LDH composite beads.

Objectives : The adsorption characteristics of Fe, Cd, and Mn in aqueous solution using zeolite and FeS media were investigated by the adsorption isotherm and kinetic model analysis.Methods : The adsorption characteristics of the heavy metals (Fe, Mn, Cd) were investigated using Langmuir or Freundlich adsorption isotherm. The analysis of pseudo-first or pseudo-second order reaction was also attempted to evaluate the rate limiting factor such as molecular diffusion or chemical adsorption on the absorbents.Results and discussion : The adsorption of the heavy metals on the zeolite and FeS media was more suitable for the Langmuir adsorption isotherm, representing that mono-layer absorption on the surface and no interaction between the absorbed solutes. The order of adsorption preference to zeolite was Fe > Cd > Mn, whereas the order of adsorption preference to FeS media was Cd > Fe > Mn. The adsorption kinetics of zeolite and FeS media were more suitable for pseudo-secondary reactions than for pseudo-primary reaction.Conclusions : The absorption capacity of FeS media for the heavy metals (Fe, Cd and Mn) in aqueous solution was higher than that of zeolite. The adsorption pattern was suitable for the Langmuir adsorption isotherm, and has kinetic characteristic by chemisorption.

The fishing industry produces waste such as viscera, which is an environmental problem for many countries. Obtaining protein from these wastes are useful for the food industry. In this study, the chemical composition, amino acid profile, solubility, digestibility and thermal properties of Yamú protein isolate (PI) and its hydrolysates obtained by enzymatic hydrolysis were characterized. The hydrolysates (0.05, 0.1, 0.5, 1 and 2% w/v) were mixed with a sodium alginate-based solution to form an edible coating solution (ECS). Antioxidant capacity antimicrobial activity, Zeta potential (ζ) and adsorption kinetics properties were determined. PI contains 88% (w/w) protein showing better solubility, digestibility and thermal stability properties. The hydrolysate concentrations with DPPH inhibitory ECS were 0.1 and 0.5% (w/v). The kinetic properties of ECS showed good stability and excellent adsorption. These results suggest that this Yamú protein has high nutritional potential as an ingredient for the production of functional foods.

Prim-O-glucosylcimifugin, cimifugin and 5-O-methylvisamminoside are three major chromone derivatives of Saposhnikovia divaricata that have many pharmacological activities, such as anti-inflammatory and antitumor activities. In the present work, an effective method for the simultaneous separation of prim-O-glucosylcimifugin, cimifugin and 5-O-methylvisamminoside with high purities was established using HPD-300 resin coupled with preparative high-performance liquid chromatography. The adsorption kinetics curves of the three compounds on the HPD-300 resin were studied and found to fit well according to the pseudo-second-order equation. The adsorption isotherm results indicated that the adsorption process of the three compounds was exothermic. After a one-run treatment with the resin, the contents of prim-O-glucosylcimifugin, cimifugin and 5-O-methylvisamminoside increased from 0.29%, 0.06% and 0.37% to 13.07%, 2.83% and 16.91% with recovery yields of 76.38%, 78.25% and 76.73%, respectively. Finally, the purities of the three compounds were found to reach more than 95% after further separation using preparative high-performance liquid chromatography. The method developed in this study was effective and could simultaneously separate three chromones from Saposhnikovia divaricate. The experimental results also showed that the HPD-300 resin is suitable for the separation of chromone derivatives. This article is protected by copyright. All rights reserved.

Zeolite is a class of microporous crystalline materials widely used in heterogeneous catalysis. Over the past decades, theoretical simulations, particularly those based on first principles calculations, have advanced significantly the understandings on zeolite, from structure to adsorption kinetics and to catalytic reactivity. The machine learning (ML) methods developed in recent years further boost the ability of theory for unraveling the interplay between the synthetic conditions and the zeolite structure and functionality. This short review overviews the theoretical insights into the role of zeolite framework in zeolite stability and catalysis revealed from atomic simulation in recent years. We will mainly focus on two key aspects: (i) the theory on zeolite stability, including the templating effect of structure directing agents and the zeolite bonding pattern analysis; (ii) the confinement effect of zeolite pores that affects the catalytic conversion of molecules in zeolite. The future directions of theoretical simulation are also discussed.

In our research, a type of cyclodextrin-based polycarboxylic acid polymer (BTCA-β-CD) was prepared by cross-linking β-cyclodextrin (β-CD) and 1,2,3,4-butanetetracarboxylic acid (BTCA) with a green and facile methods, and the adsorption performance of radionuclides such as U(VI) and Eu(III) were systematically studied through batch testing. The results revealed that the obtained maximum adsorption values of BTCA-β-CD for U(VI) and Eu(III) ions were 175.6 and 165.4 mg/g, respectively. The adsorption kinetics on both adsorbents followed pseudo-second-order model. A plausible adsorption mechanism was explored by related characterization, verifying the carboxyl and hydroxyl groups of the polymer work together as adsorption sites.

Waste chicken feathers are the ideal precursor for the production of low-cost N-enriched biochar. KOH-modified N-enriched biochar (KNB) containing 15.92 wt% N was successfully prepared using waste chicken feathers. The adsorption kinetics results showed that KNB had rapid Cd (2 h) and Pb (1 h) adsorption rates. The Cd and Pb adsorption capacities of KNB (the values of KF were 22.324 (Cd) and 119.654 (Pb) mg1−(1/n)·L1/n·g−1) were 7.07 and 26.52 times higher than those of the original biochar based on the adsorption isotherm results. The KNB was stable at pH 3–6 and had stronger co-adsorption capacities in double-ion systems. Based on the adsorption experiments and various characterization methods, we concluded that the primary Cd and Pb adsorption mechanisms of KNB involved electrostatic interactions, cation-π interactions, complexation, and K+ exchange. The precipitation mechanism could partially account for Pb adsorption but not for Cd adsorption. KOH modification enhanced the electronegativity of biochar and then increased the electrostatic attraction. Surface O- and N-containing functional groups were involved in Cd and Pb adsorption. Graphitic-N, oxidised-N, and O C O were the main active adsorption groups, the relative contents of which increased after KOH modification, thus increasing the Cd and Pb adsorption performance. Therefore, KNB can be used as a fast and highly efficient adsorption agent to remove Cd and Pb from wastewater containing either Cd and Pb or a combination of these two metals.

A model has been proposed for gas transfer through a composite polymer membrane taking into account the influence of adsorption kinetics on the surfaces of a selective layer. An analytical expression has been obtained that describes the gas transfer with regard to a finite adsorption rate and is consistent with the corresponding experimental data on gas permeability. It has been shown that the effect of the finite adsorption rate on the gas transfer increases with a decrease in the thickness of the selective polymer layer and should be taken into account along with diffusion, when describing and analyzing the transfer through composite membranes with active layers thinner than 1 μm. It has been found that, at comparable rates of adsorption and diffusion, the permeability of a composite membrane is governed by the thickness of the selective layer and the surface porosity of a support, thus being in consistent with experimental data on gas transfer through composite membranes.

Drinking water contamination by fluoride component (F-) is considered as a main public problem in Basra city. The current study highlights on the removal of (F-) from drinking water using effective and low cost materials namely, banana shell and new technical that prepared from orange shell loaded with Zirconyl chloride solutions (Z-r4 (O-H)8 (H2-O)16] Cl8 (H2-O)12) to develop active adsorption sites for fluoride . High removal efficiency of 94.4 was achieved using fixed bed column loaded (Zc-dejr) under optimum operating conditions, 15.1 ppm of feed concentration, 4.5 pH of feed solution and 4 cm of bed depth. Result of breakthrough profile showed that Thomas was coincided well with the experimental data. Two model, Pseude first order and Pseudo second order where used for finding the mechanism of adsorption kinetics for fluoride (F-) removal by two-bio adsorbents. The result showed that the external adsorption besides to the intra-particle diffusion contributes to the rate influential step. Lagmaier model gives the better result model for the two adsorbents then Temkin isotherm model (TIM). The final concentration of fluoride in treated water with the banana shell adsorbent was 1 mg/l, and with the new solution (Z-r4 (O-H)8(H2-O)16] Cl8 (H2-O)12 ) was 0.5 mg /l which is acceptable with the standard World Health Organization (WHO). http://dx.doi.org/10.30572/2018/kje/090301

It has been observed that 2,4-dichlorophenol (2,4-DCP) possesses great environmental concern for its high ecotoxicity and ubiquitousness. Adsorption is one of the simplest methods to remove the 2,4...

In this study, multi-walled carbon nanotube (MWCNTs)-SiO2 composite adsorbents MWCNTs-SiO2-2, MWCNTs-SiO2-4, MWCNTs-SiO2-6 (CS2, CS4, CS6) with molar percentages of MWCNTs of 38%, 52%, and 66% were synthesized using the sol-gel method. The effects of the MWCNT content, temperature (30−60°C), water vapor concentration (1%−5%), and the number of cycles on the adsorption capacity of toluene were studied, and an adsorption kinetics analysis was performed. The results showed that the adsorption capacity for toluene at 30−60°C was AC (activated carbon)

The interactions of DNA with lysozyme in the surface layer were studied by performing infrared reflection–absorption spectroscopy (IRRAS), ellipsometry, surface tensiometry, surface dilational rheology, and atomic force microscopy (AFM). A concentrated DNA solution was injected into an aqueous subphase underneath a spread lysozyme layer. While the optical properties of the surface layer changed fast after DNA injection, the dynamic dilational surface elasticity almost did not change, thereby indicating no continuous network formation of DNA/lysozyme complexes, unlike the case of DNA interactions with a monolayer of a cationic synthetic polyelectrolyte. A relatively fast increase in optical signals after a DNA injection under a lysozyme layer indicates that DNA penetration is controlled by diffusion. At low surface pressures, the AFM images show the formation of long strands in the surface layer. Increased surface compression does not lead to the formation of a network of DNA/lysozyme aggregates as in the case of a mixed layer of DNA and synthetic polyelectrolytes, but to the appearance of some folds and ridges in the layer. The formation of more disordered aggregates is presumably a consequence of weaker interactions of lysozyme with duplex DNA and the stabilization, at the same time, of loops of unpaired nucleotides at high local lysozyme concentrations in the surface layer.

Three types of precursor microparticles based on glycidyl methacrylate, hydroxyethyl methacrylate and one of the following three crosslinking agents (mono-, di- or triethylene glycol dimethacrylate) were prepared using the suspension polymerization technique. The precursor microparticles were subsequently used to obtain three types of hybrid microparticles. Their synthesis took place by grafting sodium hyaluronate, in a basic medium, to the epoxy groups located on the surface of the precursor microparticles. Both types of the microparticles were characterized by: FTIR spectroscopy, epoxy groups content, thermogravimetric analysis, dimensional analysis, grafting degree of sodium hyaluronate, SEM and AFM analyses, and specific parameters of porous structures (specific surface area, pore volume, porosity). The results showed that the hybrid microparticles present higher specific surface areas, higher swelling capacities as well as higher adsorption capacities of antimicrobial drugs (metronidazole). To examine the interactions between metronidazole and the precursor/hybrid microparticles the adsorption equilibrium, kinetic and thermodynamic studies were carried out. Thus, it was determined the performance of the polymer systems in order to select a polymer–drug system with a high efficiency. The release kinetics reflect that the release mechanism of metronidazole in the case of hybrid microparticles is a complex mechanism characteristic of anomalous or non-Fickian diffusion.

Water pollution by dyes is a huge environmental problem; there is a necessity to produce new decolorization methods that are effective, cost-attractive, and acceptable in industrial use. Magnetic cyclodextrin polymers offer the advantage of easy separation from the dye solution. In this work, the β-CD-EPI-magnetic (β-cyclodextrin-epichlorohydrin) polymer was synthesized, characterized, and tested for removal of the azo dye Direct Red 83:1 from water, and the fraction of non-adsorbed dye was degraded by an advanced oxidation process. The polymer was characterized in terms of the particle size distribution and surface morphology (FE-SEM), elemental analysis (EA), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), infrared spectrophotometry (IR), and X-ray powder diffraction (XRD). The reported results hint that 0.5 g and pH 5.0 were the best conditions to carry out both kinetic and isotherm models. A 30 min contact time was needed to reach equilibrium with a qmax of 32.0 mg/g. The results indicated that the pseudo-second-order and intraparticle diffusion models were involved in the assembly of Direct Red 83:1 onto the magnetic adsorbent. Regarding the isotherms discussed, the Freundlich model correctly reproduced the experimental data so that adsorption was confirmed to take place onto heterogeneous surfaces. The calculation of the thermodynamic parameters further demonstrates the spontaneous character of the adsorption phenomena (ΔG° = −27,556.9 J/mol) and endothermic phenomena (ΔH° = 8757.1 J/mol) at 25 °C. Furthermore, a good reusability of the polymer was evidenced after six cycles of regeneration, with a negligible decline in the adsorption extent (10%) regarding its initial capacity. Finally, the residual dye in solution after treatment with magnetic adsorbents was degraded by using an advanced oxidation process (AOP) with pulsed light and hydrogen peroxide (343 mg/L); >90% of the dye was degraded after receiving a fluence of 118 J/cm2; the discoloration followed a pseudo first-order kinetics where the degradation rate was 0.0196 cm2/J. The newly synthesized β-CD-EPI-magnetic polymer exhibited good adsorption properties and separability from water which, when complemented with a pulsed light-AOP, may offer a good alternative to remove dyes such as Direct Red 83:1 from water. It allows for the reuse of both the polymer and the dye in the dyeing process.

Carbon capture from large sources and ambient air is one of the most promising strategies to curb the deleterious effect of greenhouse gases. Among different technologies, CO2 adsorption has drawn widespread attention mostly because of its low energy requirements. Considering that water vapor is a ubiquitous component in air and almost all CO2-rich industrial gas streams, understanding its impact on CO2 adsorption is of critical importance. Owing to the large diversity of adsorbents, water plays many different roles from a severe inhibitor of CO2 adsorption to an excellent promoter. Water may also increase the rate of CO2 capture or have the opposite effect. In the presence of amine-containing adsorbents, water is even necessary for their long-term stability. The current contribution is a comprehensive review of the effects of water whether in the gas feed or as adsorbent moisture on CO2 adsorption. For convenience, we discuss the effect of water vapor on CO2 adsorption over four broadly defined groups of materials separately, namely (i) physical adsorbents, including carbons, zeolites and MOFs, (ii) amine-functionalized adsorbents, and (iii) reactive adsorbents, including metal carbonates and oxides. For each category, the effects of humidity level on CO2 uptake, selectivity, and adsorption kinetics under different operational conditions are discussed. Whenever possible, findings from different sources are compared, paying particular attention to both similarities and inconsistencies. For completeness, the effect of water on membrane CO2 separation is also discussed, albeit briefly.

This study investigated the preparation of super sand substance and used it as an effective adsorbent for the removal of two different dyes methylene blue (basic) and methyl orange (acidic). The initial concentration range of dyes that were used in the adsorption process was (50−200) ppm with a temperature range (20−35) °C, the surface characteristics of graphite, graphene oxide, and coated sand were investigated by AFM test. Three adsorption kinetics models were applied to the experimental data in this study, pseudo−first order, pseudo−second order, and interparticle diffusion model. The result was showed that the experimental data corresponded with pseudo−second order kinetic model with confidence level R2= 0.99.

Adsorption isotherms of Ni (II) and Cu (II) ions by alumino-silicates, modified with N, N'-bis (3-triethoxysilylpropyl) thiocarbamide (BTM-3), and HCl, were obtained. The adsorption kinetics of heavy metal ions is studied, using the kinetic pseudo-first and pseudo-second order models. It is shown that, when alumino-silicates are modified, the rate and energy of adsorption increase. It is established that the kinetics of the adsorption of the studied ions is best described by a pseudo-second order model. The maximum value of the adsorption rate constant of 33.7∙10-5 g/ (mmol min) corresponds to nickel (II) ions for alumino-silicates, modified with HCl. The maximum value of the adsorption rate constant value of 2.91∙10-5 g/ (mmol min) for alumino-silicates, modified with BTM-3, corresponds to Cu (II) ions.

Mesoporous MgO is a promising candidate for CO₂ capture. In this study, MgO pellets were activated via hydration and the effects of the process on the texture, structures, and CO₂ adsorption properties of the pelletized MgO adsorbents were systematically studied. Two adsorption kinetics models were used to investigate the CO₂ adsorption kinetics of the pelletized MgO adsorbents. Simultaneously, their kinetic parameters and the influence of adsorption temperatures were determined. It was found that a 3D, flaky, inter-connected network structure appeared after hydration. The hydration process significantly improved the pore structure of the adsorbent and thereby improved the CO₂ adsorption capacity and equilibrium rate constant. The increase in CO₂ adsorption capacity was attributed to the development of their structure rather than the reaction of Mg(OH)₂ with CO₂. The results of a kinetics study showed that a pseudo-second-order model was suitable for predicting the entire adsorption process. Meanwhile, the equilibrium kinetics rate constant of CO₂ capture increased with adsorption temperature, but the initial adsorption rate was mainly related to the texture and structures of the adsorbents. Consequently, hydration by steam or liquid water was deemed an effective method for improving the adsorption performance of MgO pellets, and the hydrated adsorbents were suitable for use in practical CO₂ capture.