Search

In this work, biopolymer chitosan and natural clay were used to obtain composite materials. The overall aim of this study was to improve the properties (porosity, thermal stability and density) of pure chitosan beads by the addition of clay and to obtain a chitosan-based composite material for the adsorption of heavy metals from an aqueous solution, using Mongolian resources, and to study the adsorption mechanism. The natural clay was pre-treated with acid and heat to remove the impurities. The chitosan and pre-treated clay were mixed in different ratios (8:1, 8:2 and 8:3) for chemical processing to obtain a composite bead for the adsorption of chromium ions. The adsorption of Cr(III) and Cr(VI) was studied as a function of the solution pH, time, temperature, initial concentration of the chromium solution and mass of the composite bead. It was found that the composite bead obtained from the mixture of chitosan and treated clay with a mass ratio of 8:1 and 8:2 had the highest adsorption capacity (23.5 and 17.31 mg·g−1) for Cr(III) and Cr(VI), respectively, in the optimum conditions. The properties of the composite materials, prepared by mixing chitosan and clay with a ratio of 8:1 and 8:2, were investigated using XRD, SEM–EDS, BET and TG analysis. The adsorption mechanism was discussed based on the XPS analysis results. It was confirmed that the chromium ions were adsorbed in their original form, such as Cr(III) and Cr(VI), without undergoing oxidation or reduction reactions. Furthermore, Cr(III) and Cr(VI) were associated with the hydroxyl and amino groups of the composite beads during adsorption. The kinetic, thermodynamic and isothermal analysis of the adsorption process revealed that the interaction between the chitosan/clay composite bead and Cr(III) and Cr(VI) ions can be considered as a second-order endothermic reaction, as such the adsorption can be assessed using the Langmuir isotherm model. It was concluded that the composite bead could be used as an adsorbent for the removal of chromium ions. [ABSTRACT FROM AUTHOR]

Dyes pose a significant environmental hazard due to their widespread use and tenacity in water bodies, resulting in adverse ecological and health effects. Many strategies have been investigated for the removal of dyes, and adsorption has emerged as a viable technique. Biochar-based adsorbents provide a sustainable alternative because of their high adsorption capacity, variable surface characteristics, and widespread availability. Biochar has improved adsorption properties similar to specific surface area, porosity, and total pore volume when mixed with metal nanoparticles due to synergistic interactions. It is crucial to comprehend the adsorption isotherm and kinetic models that control dye adsorption onto biochar because they provide insight into the mechanism and equilibrium behavior, respectively. The adsorption process's viability and energetics are further clarified by thermodynamic studies. Experiments and parameter optimization are guided by computational studies that use methods such as density functional theory (DFT) and response surface methodology (RSM) to optimize adsorption processes by giving insight into the system's relationship between multiple independent variables and multiple response variables and electron structure. This review also highlights the cost-effectiveness and sustainability of biochar/metal nanoparticle composites by discussing techniques for their regeneration and reuse and also explains the adsorption mechanism of dye by biochar/metal nanoparticle composites.

Exploring the ratio of metal centers to organic ligands and the amount of DMF are important to improve the stability and adsorption efficiency of MOF materials as adsorbents. In this work, MIL101(Fe)-Na2CO3 was successfully obtained by modification with formic acid, sodium carbonate, carbon nanotubes, and moieties. The adsorption efficiency of MIL-101(Fe) on Cr(VI) was greatly improved, and the removal efficiency was able to reach 100% in 20 min with a maximum adsorption capacity of 20 mg/g. The inhibition order of the competing anions for the removal of hexavalent chromium was as follows: Cl− < NO3− < SO42−. The analysis of the adsorption thermodynamic model found that the adsorption of MIL101(Fe)-Na2CO3 for Cr(VI) showed spontaneous heat-absorbing and entropy-increasing chemisorption behavior. When using NaOH as the eluent and HCl as the regeneration stabilizer, MIL-101(Fe)-Na2CO3 had good adsorption capacity in multiple cycles. [ABSTRACT FROM AUTHOR]

Contamination of water by toxic dyes is a serious environmental problem. Adsorbents prepared by an environmentally safe route have stood out for application in pollutant removal. Herein, iron oxide–based nanomaterial composed of Fe(III)-OOH and Fe(II/III) bound to proanthocyanidins, with particles in the order of 20 nm, was prepared by green synthesis assisted by extract of açaí (Euterpe oleracea Mart.) berry seeds from an agro-industrial residue. The nanomaterial was applied in the adsorption of cationic dyes. Screening tests were carried out for methylene blue (MB), resulting in an outstanding maximum adsorption capacity of 531.8 mg g−1 at 343 K, pH 10, 180 min. The kinetics followed a pseudo-second-order model and the isotherm of Fritz-Schülnder provided the best fit. Thermodynamic data show an endothermic process with entropy increase, typical of chemisorption. The proposed mechanism is based on the multilayer formation over a heterogeneous adsorbent surface, with chemical and electrostatic interactions of MB with the iron oxide nanoparticles and with the proanthocyanidins. The high adsorption efficiency was attributed to the network formed by the polymeric proanthocyanidins that entangled and protected the iron oxide nanoparticles, which allowed the reuse of the nanomaterial for seven cycles without loss of adsorption efficiency. [ABSTRACT FROM AUTHOR]

In this work, biopolymer chitosan and natural clay were used to obtain composite materials. The overall aim of this study was to improve the properties (porosity, thermal stability and density) of pure chitosan beads by the addition of clay and to obtain a chitosan-based composite material for the adsorption of heavy metals from an aqueous solution, using Mongolian resources, and to study the adsorption mechanism. The natural clay was pre-treated with acid and heat to remove the impurities. The chitosan and pre-treated clay were mixed in different ratios (8:1, 8:2 and 8:3) for chemical processing to obtain a composite bead for the adsorption of chromium ions. The adsorption of Cr(III) and Cr(VI) was studied as a function of the solution pH, time, temperature, initial concentration of the chromium solution and mass of the composite bead. It was found that the composite bead obtained from the mixture of chitosan and treated clay with a mass ratio of 8:1 and 8:2 had the highest adsorption capacity (23.5 and 17.31 mg·g−1) for Cr(III) and Cr(VI), respectively, in the optimum conditions. The properties of the composite materials, prepared by mixing chitosan and clay with a ratio of 8:1 and 8:2, were investigated using XRD, SEM–EDS, BET and TG analysis. The adsorption mechanism was discussed based on the XPS analysis results. It was confirmed that the chromium ions were adsorbed in their original form, such as Cr(III) and Cr(VI), without undergoing oxidation or reduction reactions. Furthermore, Cr(III) and Cr(VI) were associated with the hydroxyl and amino groups of the composite beads during adsorption. The kinetic, thermodynamic and isothermal analysis of the adsorption process revealed that the interaction between the chitosan/clay composite bead and Cr(III) and Cr(VI) ions can be considered as a second-order endothermic reaction, as such the adsorption can be assessed using the Langmuir isotherm model. It was concluded that the composite bead could be used as an adsorbent for the removal of chromium ions.

This study investigates the dyeing effects of chestnut leaf extract on tussah silk and aspires to create bio-colored and ultraviolet-resistant textiles. The results proved that post-mordanting with aluminum potassium sulfate and ferrous sulfate yielded better results than direct dyeing, the color strength value with ferrous sulfate mordant reached 10.9, and the color fastness of tussah silk with post-mordanting was rated above 4. Furthermore, the ultraviolet protection factor values reached 17, 39, 45, and 53 with control, direct dyeing, and post-mordanting with aluminum potassium sulfate and ferrous sulfate, respectively, revealing that the chestnut leaf extract could be a potential ultraviolet protection agent to increase the ultraviolet protection performance on tussah silk. In addition, the adsorption process and thermodynamic characteristics of chestnut leaf extract on tussah silk were examined. The results suggested that the Langmuir isotherm model adequately described the thermodynamic behavior of chestnut leaf extract on tussah silk. The positive enthalpy change indicated that the adsorption process was an endothermic process. [ABSTRACT FROM AUTHOR]

A new hydrogel, based on chitosan crosslinked with 2-chlorophenyl-bis(6-amino-1,3-dimethyluracil-5-yl) methane, (2Clph-BU-Cs), has been successfully created. Various instrumental techniques such as elemental analysis, FTIR, SEM, and XRD were used to prove its structure. Its removal efficiency for anionic Congo red (CR) dye under different conditions for industrial wastewater treatment was studied. For optimizing the conditions to maximize CR dye removal, the impacts of temperature, contact time, pH, and initial concentration of the dye on adsorption capacity were investigated. The removal of the dye was pH-dependent, with a much higher value achieved at pH 4 than at pH 7 and 9. The maximum adsorption capacity of the hydrogel was 93.46 mg g−1. The model of adsorption process was fitted to the pseudo-second-order kinetic model. The intraparticle diffusion demonstrated the multi-step nature of the adsorption process. The thermodynamic results showed that the adsorption process was endothermic because of the positive value of enthalpy (43.70 kJ mol−1). The process of adsorption at high temperatures was spontaneous, according to the values of ∆G0. An increase in randomness was seen in the value of ∆S°. Generally, the investigated hydrogel has the potential to be used as a promising effective reusable adsorbent for industrial wastewater remediation. [ABSTRACT FROM AUTHOR]

Exploring the ratio of metal centers to organic ligands and the amount of DMF are important to improve the stability and adsorption efficiency of MOF materials as adsorbents. In this work, MIL101(Fe)-Na2CO3 was successfully obtained by modification with formic acid, sodium carbonate, carbon nanotubes, and moieties. The adsorption efficiency of MIL-101(Fe) on Cr(VI) was greatly improved, and the removal efficiency was able to reach 100% in 20 min with a maximum adsorption capacity of 20 mg/g. The inhibition order of the competing anions for the removal of hexavalent chromium was as follows: Cl− < NO3− < SO42−. The analysis of the adsorption thermodynamic model found that the adsorption of MIL101(Fe)-Na2CO3 for Cr(VI) showed spontaneous heat-absorbing and entropy-increasing chemisorption behavior. When using NaOH as the eluent and HCl as the regeneration stabilizer, MIL-101(Fe)-Na2CO3 had good adsorption capacity in multiple cycles.

Three sodium polyacrylate copolymers PD0x (Poly acrylic acid-co-sodium 4-vinylbenzenesulfonate or PD01; Poly acrylic acid-co-sodium 4-vinylbenzenesulfonate-co-hydroxyethyl methacrylate or PD02 and Poly methyl methacrylate-co-acrylic acid-co-sodium 4-vinylbenzenesulfonate-co-hydroxyethyl methacrylate or PD03) were synthesized as water-based dispersants for grinding red–brown pigment ZnFe1.2Cr0.8O4 particles prepared by the solid phase method (S-ZnF). The particle size distribution, viscosity of suspensions, and adsorption capacity of dispersants were explored by laser particle size analysis, viscometer, and thermogravimetry (TG), respectively. The application of 2 wt.% dispersant PD02 in the S-ZnF suspension ground for 90 min can deliver a finer product with the narrower particle size distribution. The added dispersant PD02 in the grinding process of the S-ZnF particles exhibits a suitable viscosity of the suspension and generates more hydrogen bonds on the S-ZnF particle surface. The sulfonic acid groups (SO3−) and carboxylic acid groups (-COO−) in the dispersant PD02 can also provide a strong charge density, which is favorable for the dispersion and grinding of the S-ZnF particles in the suspensions. Furthermore, the adsorption behavior of polymeric dispersant PD02 adsorbed on the S-ZnF particles surface was simulated and analyzed by adsorption thermodynamic models and adsorption kinetic models. It is indicated that the adsorption thermodynamic behavior of dispersant PD02 adsorbed on the S-ZnF particles surface follows the Langmuir model, and the adsorption process is endothermic and a random process with increased confusion during the grinding process. In addition, the adsorption kinetics of dispersant PD02 adsorbed on the S-ZnF particles surface are more in line with the pseudo-first-order kinetic models. Therefore, the adsorption process of dispersant PD02 on the S-ZnF particles surface can be considered as a single-surface adsorption process. [ABSTRACT FROM AUTHOR]

Irrigation of carbonate-rich agricultural soils with arsenic (As)-contaminated water leads to the accumulation of As in these soils. In this regard, there is an opportunity to adsorb and fix the As in soil and decrease the As transportation to the plants and subsequently the human food chain. So, the present study aimed to investigate the adsorption–desorption characteristics of As in calcareous soils and the potential of As fixation over time. First, to achieve this purpose, 53 soil samples were gathered from the study site and after the laboratory analysis, the soils were categorized into four groups based on their physicochemical properties. Then, four representative samples of these groups were selected, namely soil 1, soil 2, soil 3, and soil 4. Afterward, the As adsorption–desorption was investigated in a lab-scale batch experiment. Next, the effect of age was assessed by incubating the As-adsorbed soils for 60 days, and to study the impact of temperature, the adsorption was performed at four temperature levels (10, 20, 30, and 40 °C). Finally, the isotherm models were fitted to experimental data, and the amount of loosely and tightly held As was quantified. Results revealed that the As adsorption isotherms were L-type, in which As adsorption increased with the increase of As loading. The double-site Langmuir (DSL) estimated that a limited amount of As was adsorbed on high-energy surfaces and a large amount of As was adsorbed on low-energy surfaces. Desorption results showed that a significant amount of As desorbed immediately; however, the desorption significantly decreased with the increase of age, especially at low equilibrium concentrations. By aging the loosely held As transformed into non-labile forms so that in soils 1, 2, 3, and 4, the fraction of As adsorbed on high-energy surfaces increased from 72.5, 93.2, 63.2, and 123 mg/kg to 167, 141, 70.6, and 196 mg/kg, respectively, and the fraction of As adsorbed on low-energy surfaces decreased from 397, 256, 202, and 317 mg/kg to 182, 238, 173, and 172 mg/kg, respectively (after aging for 60 days). Aging proved to be a promising solution for decreasing As transport into the human food chain and could be employed for crops with longer irrigation cycles. ΔHad values were positive and varied from 9.26 to 13.0 kJ/mol, confirming the endothermic nature of adsorption. ΔGad values were negative and varied from − 18.8 to − 22.8 kJ/mol at all temperatures, demonstrating the spontaneous nature of adsorption. [ABSTRACT FROM AUTHOR]

The adsorption properties of the lanthanum-doped mesoporous silica gel modified with nickel and silver (La–Ni/MC, La–Ag/MC) synthesized by the template method were studied by gas chromatography. The textural characteristics of the obtained materials were studied by the methods of low-temperature nitrogen adsorption-desorption, atomic emission spectroscopy (ICP), X-ray phase analysis (XRD), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM). The thermodynamic characteristics of adsorption (differential heats and entropies) of test organic compounds were obtained by the inverse gas chromatography. It has been established that doping and modification leads to changes in the heats of adsorption for compounds prone to various types of specific interactions. It is shown that mesoporous silica gel doped with lanthanum and modified with nickel exhibits more pronounced adsorption properties with respect to the studied sorbates. [ABSTRACT FROM AUTHOR]

[Display omitted] • SDS is not only a sulfur source, but also plays an additional role in the pores. • High sulfur carbon was prepared by simple hydrothermal reaction of SDS and glucose. • Ultra- microporous and S functionalities determine CO 2 and CH 4 uptake. • Outstanding CO 2 and CH 4 uptake & high selectivity for CO 2 /N 2 and CH 4 /N 2 separation. • The mechanism of activated carbon prepared by KOH and SDS was proposed. Series of sulfur-doped porous carbons were prepared by using glucose as carbon source and sodium dodecyl sulfate as sulfur source to synthesize sulfur-based carbon precursor and KOH as activator. Pore structure parameters and sulfur content of the prepared carbon materials could be facility regulated by controlling the ratio of KOH/sulfur-based carbon precursor and activation temperature, and their adsorptive separation properties towards CO 2 and CH 4 were investigated. Results showed that the higher the ultra-microporous volume and the S content of the prepared sulfur-doped porous carbon were, the larger the CO 2 and the CH 4 adsorption capacity were. The maximum adsorption capacity of CO 2 (6.54 mmol/g, 273.15 K and 101 kPa, hereinafter) and CH 4 (2.98 mmol/g), and the excellent selectivity of CO 2 /N 2 (75.7) and CH 4 /N 2 (22.8) were achieved by ACS-700-2 because of its higher ultra-microporous pore volume and the highest S content. Permeation experiment, cycle stability test and adsorption thermodynamics experiment show that the prepared S-doped porous carbon had good application potential in the separation and enrichment of CO 2 in flue gas and CH 4 in coalbed methane. In addition, the pore formation mechanism of sulfur-doped porous carbon was discussed. [ABSTRACT FROM AUTHOR]

Cationic synthetic dyes are one of the hazards in aqueous solutions that can affect the health of humans and living organisms. In the current work, polyacrylamide (PAM)- g -gelatin hydrogel and modified PAM- g -gelatin hydrogel using activated carbon of Luffa cylindrica (ACL) and ACL/Mg–Fe LDH were applied to eliminate crystal violet (CV), a cationic dye, from water media. The hydrogels were synthesized using free radical polymerization approach, and the hydrogels were characterized using FTIR, XRD, TGA-DTG, BET, SEM, and EDX-Map. The surface area of ACL, ACL/Mg–Fe LDH, PAM-g-gelatin, PAM-g-gelatin/ACL, and PAM-g-gelatin/ACL/Mg–Fe LDH were 99.71, 141.99, 0.74, 1.47, and 1.65 m2/g, respectively, which shows that the presence of ACL and ACL/Mg–Fe LDH improved the area of the hydrogels. The maximum abatement of CV using PAM-g-gelatin (92.81%), PAM-g-gelatin/ACL (95.71%), and PAM-g-gelatin/ACL/Mg–Fe LDH (98.25%) was obtained at pH = 9, temperature 25 °C, 10 mg/L CV, 60 min time, and adsorber dose of 2 g/L (for PAM-g-gelatin) and 1.5 g/L (other samples). The value of thermodynamic factors confirmed that the abatement process is exothermic and spontaneous. The kinetics data followed the pseudo-second kinetic (PSO) model. The Langmuir isotherm model had a more remarkable ability to describe the equilibrium data. The maximum adsorption capacity for PAM-g-gelatin, PAM-g-gelatin/ACL, and PAM-g-gelatin/ACL/Mg–Fe LDH was determined 35.45, 39.865, and 44.952 mg/g, respectively. Generally, the studied hydrogels can eliminate dyes from wastewater and be used as effective adsorbers. • A new polyacrylamide- g -gelatin/ACL/Mg–Fe LDH composite hydrogel was produced. • The hydrogel had an area of 1.65 m2/g and used to remove crystal violet (CV). • The maximum CV abatement (98.25%) was obtained at pH 9 and 10 mg/L CV. • The data followed the pseudo-second-order and Langmuir models (R2 > 0.99). • Textile wastewater was effectively cleaned with hydrogel. [ABSTRACT FROM AUTHOR]

The carbon nanotubes grafted methylene blue molecularly imprinted polymers (CNT-MB-MIPs) were prepared by grafting aminated carbon nanotubes (CNTs) and copolymerized in the presence of template molecules methylene blue (MB), functional monomers, crosslinkers, and initiators. The results from structural analyses indicate that CNTs were successfully grafted onto the molecularly imprinted polymers (MIPs). The adsorption experiments showed that the adsorption capacity can be affected by grafting CNTs. The adsorption capacity of CNT-MB-MIPs on MB can reach 2793 mg g − 1 while the initial concentration of MB was 12 g L − 1 , which was higher than that of MB molecularly imprinted polymers (MB-MIPs). Meanwhile, compared with MB-MIPs, CNT-MB-MIPs had a lower adsorption capacity for iron ions, indicating that CNT-MB-MIPs could inhibit the adsorption of iron ions. Adsorption kinetics study showed that the adsorption mechanism of the polymer for MB was in good agreement with the quasi-second-order kinetics model ( R 2 = 0. 9 9 7 8) and the adsorption mechanism for iron ions was also in good agreement with the Bangham kinetics model ( R 2 = 0. 9 4 7 5). The adsorption isotherm showed that the adsorption process of the two adsorbents was mainly monolayer chemisorption. The remarkable adsorption capacity of CNT-MB-MIPs may be due to the enlargement of adsorption sites on MIPs surface by CNT-NH2 grafting. At the same time, it can inhibit the adsorption of iron ions, because part of the carboxyl groups in CNT-MB-MIPs are bonded by CNTs, led to few carboxyl groups sites left for adsorbing iron ions, thereby the complex between carboxyl groups and iron ions were inhibited. [ABSTRACT FROM AUTHOR]

Geothermal water resources are being exploited widely in many areas to relieve pressure on water resources generally. Excessive Mn2+ concentration in geothermal water will seriously reduce its utilization rate. Therefore, this study investigated the removal of Mn2+ from simulated geothermal water by manganese sand. The Mn2+ removal rate from simulated water with a concentration of 10 mg l−1 by 2 g manganese sand at 298, 323, 343 and 363 K was more than 90%. The removal efficiency of Mn2+ is influenced by adsorbent dosage, adsorbent particle size, initial Mn2+ concentration and competing ions, and less so by a pH of 5–9. A pseudo-first-order kinetic model fits the adsorption data better than a pseudo-second-order model. The pseudo-first-order adsorption rate constants (K1) ranged from 0.14 to 0.5 h−1 as the temperature increased from 298 to 363 K. The Langmuir isotherm model fits the adsorption data better than the Freundlich and Temkin isotherm models. The maximum monolayer adsorption capacities (qm) obtained by the Langmuir isotherm model fitting were 0.91/1.02/1.22/1.23 mg g–1 at 298/323/343/363 K. Thermodynamic studies revealed that the adsorption was endothermic and physical in nature. These findings suggest that the potential of manganese sand for removing Mn2+ in geothermal water is considerable. Thematic collection: This article is part of the Hydrochemistry related to exploration and environmental issues collection available at: https://www.lyellcollection.org/cc/hydrochemistry-related-to-exploration-and-environmental-issues [ABSTRACT FROM AUTHOR]

Three sodium polyacrylate copolymers PD0x (Poly acrylic acid-co-sodium 4-vinylbenzenesulfonate or PD01; Poly acrylic acid-co-sodium 4-vinylbenzenesulfonate-co-hydroxyethyl methacrylate or PD02 and Poly methyl methacrylate-co-acrylic acid-co-sodium 4-vinylbenzenesulfonate-co-hydroxyethyl methacrylate or PD03) were synthesized as water-based dispersants for grinding red–brown pigment ZnFe1.2Cr0.8O4 particles prepared by the solid phase method (S-ZnF). The particle size distribution, viscosity of suspensions, and adsorption capacity of dispersants were explored by laser particle size analysis, viscometer, and thermogravimetry (TG), respectively. The application of 2 wt.% dispersant PD02 in the S-ZnF suspension ground for 90 min can deliver a finer product with the narrower particle size distribution. The added dispersant PD02 in the grinding process of the S-ZnF particles exhibits a suitable viscosity of the suspension and generates more hydrogen bonds on the S-ZnF particle surface. The sulfonic acid groups (SO3−) and carboxylic acid groups (-COO−) in the dispersant PD02 can also provide a strong charge density, which is favorable for the dispersion and grinding of the S-ZnF particles in the suspensions. Furthermore, the adsorption behavior of polymeric dispersant PD02 adsorbed on the S-ZnF particles surface was simulated and analyzed by adsorption thermodynamic models and adsorption kinetic models. It is indicated that the adsorption thermodynamic behavior of dispersant PD02 adsorbed on the S-ZnF particles surface follows the Langmuir model, and the adsorption process is endothermic and a random process with increased confusion during the grinding process. In addition, the adsorption kinetics of dispersant PD02 adsorbed on the S-ZnF particles surface are more in line with the pseudo-first-order kinetic models. Therefore, the adsorption process of dispersant PD02 on the S-ZnF particles surface can be considered as a single-surface adsorption process.

Dyes removal from wastewater of industries is considered the prime demand of the environment. Three trimellitic anhydride isothiocyanate-cross-linked chitosan hydrogels, previously reported as novel antimicrobial agents, were investigated for the first time in this work as adsorbents for Basic Red 12 (BR 12) cationic dye. These hydrogels behave as polyanionic materials. Their adsorption capacity for the BR 12 dye increased significantly with increasing both the temperature, the solution pH and their cross-linking content. Their adsorption fitted to the pseudo-second-order kinetic model. Their adsorption isotherms conform to the Langmuir model suggesting that the adsorption nature is a monolayer having an optimum sorption capability of 38.27 mg g−1 and removal efficiency of 97.38%. The results proved that the adsorption process is remarkably proceeded by chemisorption phenomenon. The data of adsorption thermodynamics indicate that the adsorption is an endothermic process. The regeneration and reuse of the hydrogels were possible. Thus, incorporation of the functionality of the cross-linker into chitosan within the same structure efficiently enhanced its features. It is a good manner for achieving appropriate series of efficient adsorbents which are considered as favorable nominees in the field of basic dyes removal. [ABSTRACT FROM AUTHOR]

Novel Uracil-modified chitosan (UCs) adsorbent has successfully been synthesized through a four-step method during which the amino groups of chitosan have been protected, then epoxy nuclei have been incorporated, afterwards the latter have been opened using 6-amino-1,3-dimethyl uracil, and finally the amino groups have been regained via removing the protection. Its structure was checked using FTIR, XRD and SEM techniques. The adsorption capacity of UCs for anionic Congo Red (CR) dye was studied under various conditions. It decreased significantly with increasing the solution pH value and dye concentration, while increased with increasing temperature. The adsorption of UCs for CR dye at different temperatures, solution pH and dye concentrations fitted to the kinetic model of pseudo-second order and Elovich model. The intraparticle diffusion model showed that the adsorption process involves multi-step process. The isotherm of CR dye adsorption by UCs conforms to the Langmuir isotherm model indicating the monolayer nature of adsorption. The maximum monolayer coverage capacity, qmax, was 434.78 mg g−1. Studying the thermodynamic showed that the adsorption of CR dye onto UCs was endothermic as illustrated from the positive value of enthalpy (21.37 kJ mol−1). According to the values of ΔG°, the adsorption process was spontaneous at all selected temperatures. The value of ΔS° showed an increase in randomness for the adsorption of CR dye by UCs. The value of activation energy was 18.40 kJ mol−1.

Novel Cyanoguanidine-modified chitosan (CCs) adsorbent was successfully prepared via a four-step procedure; first by protection of the amino groups of chitosan, second by insertion of epoxide rings, third by opening the latter with cyanoguanidine, and fourth by restoring the amino groups through elimination of the protection. Its structure and morphology were checked using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The adsorption capacity of CCs for Congo Red (CR) dye was studied under various conditions. It decreased significantly with the increase in the solution pH value and dye concentration, while it increased with increasing temperature. The adsorption fitted to the pseudo-second order kinetic model and Elovich model. The intraparticle diffusion model showed that the adsorption involved a multi-step process. The isotherm of CR dye adsorption by CCs conforms to the Langmuir isotherm model, indicating the monolayer nature of adsorption. The maximum monolayer coverage capacity, qmax, was 666.67 mg g−1. Studying the thermodynamic showed that the adsorption was endothermic as illustrated from the positive value of enthalpy (34.49 kJ mol−1). According to the values of ΔG°, the adsorption process was spontaneous at all selected temperatures. The value of ΔS° showed an increase in randomness for the adsorption process. The value of activation energy was 2.47 kJ mol−1. The desorption percentage reached to 58% after 5 cycles. This proved that CCs is an efficient and a promising adsorbent for the removal of CR dye from its aqueous solution.

Decolorization technology is a critical problem of high-quality chemical recycling and recovery of waste poly(ethylene terephthalate) (PET) textiles. In order to deal with this problem, nitric acid-modified activated carbon (AC-HNO3) was utilized as an adsorbent for removal of C.I. Disperse Red 60 (DR60) from the glycolysis products of waste PET fabrics. The glycolysis product was bis(2-hydroxyethyl) terephthalate (BHET). The pore structure and surface properties of AC and AC-HNO3 samples were characterized by N2 adsorption, differential thermogravimetric analysis (DTG) and elemental analyses (EA). Modification with nitric acid increased the amount of oxygen groups of the activated carbon from 12.3% to 18.0% and enhanced the electrostatic attraction between dye molecules and activated carbon. The average color removal ratio of DR60 on AC-HNO3 increased into 97.6 ± 0.5%, which is better than that on raw AC (85.0 ± 1.6%). Relative whiteness of BHET increased from 40.3 ± 0.9% to 98.3 ± 1.1%. The adsorption kinetics for DR60 on the AC-HNO3 were studied using pseudo-first order and pseudo-second order models and fitted to the latter well (R 2 = 0.9999). To investigate the adsorption equilibrium behavior, Freundlich and Langmuir models were examined. The results showed that the Langmuir model provided better correlation (q max = 163.9 mg/g). The adsorption isotherms at different temperatures were used for the determination of thermodynamic parameters. Based on the data of Δ G 0, Δ H 0 and E a, the adsorption process was physisorption. [ABSTRACT FROM AUTHOR]

In this work, cobalt-aluminum-layered double hydroxide (CoAl) and its bentonite composite (Bent-CoAl) were utilized for adsorption of Cr(VI) from water. Incorporation of bentonite into layers of CoAl resulted in significant improvement in the adsorptive performance with increased BET surface area, without damaging LDH structure. The adsorption process was described by Freundlich isotherm and pseudo-second-order kinetic models. The mechanism of Cr(VI) sorption mainly involved electrostatic and chemical interactions with maximum Cr(VI) sorption value of 211.86 mg/g. This suggests that synergistic effect of bentonite into CoAl provided a superior adsorbent for decontamination of heavy metals. [ABSTRACT FROM AUTHOR]

Diatomite-based X zeolite was obtained and its crystallinity, morphology, and interface properties were investigated by XRD, BET, SEM, EDS, and XRF. The obtained X zeolite possessed a unique meso-microporous structure and showed good ion exchange properties for Cu2+ and Zn2+. The pseudo-second-order model and Langmuir isotherm model can best describe the adsorption kinetics and isotherms of Cu2+ and Zn2+, respectively. The maximal adsorption capacities of X zeolite for Cu2+ and Zn2+ were 146 and 195 mg/g at 323 K, respectively. Meanwhile, the adsorption process for Cu2+ and Zn2+ were chemical adsorption and ion exchange, respectively. Furthermore, the adsorption data turned out to be an endothermic and spontaneous process. Compared with other reported materials, the adsorption capacity of X zeolite synthesized from diatomite was among the highest. Therefore, it could be a promising adsorbent for the disposal of wastewater that contains metal ions.

The chemical cross-linking of carboxymethyl chitosan (O-CM-chitosan), as a method for its modification, was performed using trimellitic anhydride isothiocyanate to obtain novel cross-linked O-CM-chitosan hydrogel. Its structure was proven using FTIR, XRD and SEM. Its adsorption capacity for the removal of Methylene Blue (MB) dye from aqueous solution was studied. The effects of different factors on the adsorption process, such as the pH, temperature and concentration of the dye, in addition to applications of the kinetic studies of the adsorption process, adsorption isotherm and thermodynamic parameters, were studied. It was found that the amount of adsorbed MB dye increases with increasing temperature. A significant increase was obtained in the adsorption capacities and removal percentage of MB dye with increasing pH values. An increase in the initial dye concentration increases the adsorption capacities, and decreases the removal percentage. It was found that the pseudo-second-order mechanism is predominant, and the overall rate of the dye adsorption process appears to be controlled by more than one step. The Langmuir model showed high applicability for the adsorption of MB dye onto O-CM-chitosan hydrogel. The value of the activation energy (Ea) is 27.15 kJ mol−1 and the thermodynamic parameters were evaluated. The regeneration and reuse of the investigated adsorbent was investigated.

In this research, crosslinked nanocomposite (NC) films involving chitosan (CS) and various percentages of nitrogen-doped graphene quantum dot (NGQD) were prepared via ultrasonic acoustic accompanied by adding glutaraldehyde as a crosslinking agent (henceforth nominated as CCS/NGQD NC). The objective of this study is the design of a safe adsorbent of CCS/NGQD NC under easy and low-cost conditions to investigate the mechanisms of Cd(II) ion sorption and find an appropriate model for the kinetics of removal. By comparing adsorption ability of CCS/NGQD NC films 2, 5 and 8 wt% under the same conditions, the CCS NC film with 5 wt% of NGQD was selected as the best mass ratio to investigate the adsorption process. To understand the nature of the sorption behavior, the experimental data were used to calculate pseudo-first-order, pseudo-second-order, and intra-particle diffusion kinetic models, and various isotherm models in linear and nonlinear regression. In addition, some error functions were applied to detect, either linear or nonlinear model is suitable to examine the experimental data and prevent any huge mistakes. The linear Freundlich equation well describes the uptake of Cd(II) ion by CCS film and CCS/NGQD NC film 5 wt%. Based on linear Langmuir, the maximum adsorption capacities of CCS film and CCS/NGQD NC film 5 wt% were 34.46 and 35.00 mg·g−1, respectively. Kinetic analysis indicates that the mechanism of removal is described by nonlinear pseudo-second order model for CCS film and linear pseudo-second order model for the CCS/NGQD NC film 5 wt%. Also, thermodynamic parameters were analyzed in different temperatures. The obtained thermodynamic values prove that Cd(II) ion adsorption on both adsorbents is feasible, spontaneous and endothermic. Unlabelled Image • Quantum dot showed effective role in enhancing of uptake rate of Cd(II) ion by chitosan. • Latest linear and nonlinear forms of isotherm and kinetic adsorption were used. • Linear Freundlich expression was best fitted to the equilibrium data than the nonlinear. • Better interpretation of experimental data was performed by some error analyses. • From the thermodynamic data the adsorption of Cd(II) ion on adsorbents is endothermic. [ABSTRACT FROM AUTHOR]

Core-shell porphyrin-based magnetic nanocomposites with multi-functional groups were synthesized and used as effective adsorbents and crystal nuclei for removing Pb(II) from water. The effect of initial Pb(II) concentration (C 0), equilibrium time and experimental temperature on the adsorption capacity has been investigated. Under the optimized conditions, the removal rate of Pb(II) can reach 84.3% only within 5 min, more efficient than similar adsorbents. In addition, the maximum adsorption capacity of FST is up to 798.34 mg/g, which is much higher than previously reported results for removing Pb(II) in aqueous solution. Furthermore, the adsorption mechanisms were proposed based on the results of field emission scanning electron microscopy (FE-SEM), ultraviolet-visible spectroscopy (UV–vis) and X-ray diffraction tests. The adsorption processes could be well described by pseudo-second-order kinetic model regardless of C 0. However, when C 0 was <19.2 mg/L, the adsorption process was a favorable monolayer interaction, controlled by the coordination between Pb(II) and porphyrin. When the C 0 was at the range of 19.2–512 mg/L, adsorption was multilayer interaction, and the process was controlled by crystallization and limiting solubility. Moreover, density functional theory (DFT) calculations have been used to study the optimal functional group towards Pb(II), which revealed that the adsorbability of tetrapyrrolic core to Pb(II) was better than that of NH, C O and Si O Si in porphyrin. This study provides a facile method for removal of Pb(II) from aqueous solutions and offers theoretical and practical guidance on new adsorbent designs for selective removal of heavy metal ions. Unlabelled Image • A novel and effective adsorbent FST was synthesized for removing Pb(II). • FST exhibits higher adsorption capacity to Pb(II) than reported works. • Adsorption mechanisms were investigated at atomic level. • Optimal functional group was disclosed for the first time. • Proposed method offers theoretical guidance on the development of new adsorbent. [ABSTRACT FROM AUTHOR]

Abstract Due to environmental issues, wastewater treatment is a main concern for most industries and providing access to clean and affordable water is one of the big challenges. Besides, industrial wastewater contains many pollutants, one of the most toxic contaminants is organics. Currently, zeolites are widely used as an adsorbent to remove such pollutants. This study examines a surfactant modified zeolite Y (SMZY), as an applicable solution, to get over this problem. Here, zeolite Y, synthesized from bentonite, is used as an adsorbent basis. Then, it is characterized by XRD, FTIR, BET, SEM, and TGA. Next, it is modified by hexadecyltrimethyl ammonium bromide (CTAB) surfactant in different concentrations. These SMZYs are used to adsorb organic contaminants of an olefin plant wastewater. Based on adsorption capacity evaluated by several isotherms, such as Langmuir, Freundlich, Sips and Dubinin–Radushkevich, total organic carbon (TOC) content of wastewater reduced up to 89%. The optimum modification method and possible mechanism for obtaining this result is presented in the current research. Furthermore, to understand the nature of adsorption process, Van der Waals, hydrophobic, and electrostatic interactions are determined. The results indicate that adsorption process depends on both hydrophobic and electrostatic interactions. Graphical abstract Image Highlights • Zeolite Y was successfully synthesized from bentonite at atmospheric pressure. • Adsorption of organic contents from wastewater depended on the loaded surfactant. • Patchy-bilayer form of surfactant is the best modification. • The best adsorbent has removed almost 89% of organic contents from wastewater. • The forces associated with process were hydrophobic and electrostatic interactions. [ABSTRACT FROM AUTHOR]

Illite-smectite clay is a new mixed mineral of illite and montmorillonite. The ability of nano illite/smectite clay to remove Pb(II) from slightly polluted aqueous solutions has been investigated. The effects of pH, contact time, initial concentration of Pb(II), nano illite/smectite clay dosage, and temperature on the adsorption process were studied. The nano illite/smectite clay was characterized by X-Ray Diffraction (XRD), Fourier transform infrared spectrometry (FTIR), and Scanning electron microscopy (SEM). The results showed that Pb(II) was adsorbed efficiently by nano illite/smectite clay in aqueous solution. The pseudo-second-order kinetic model best described the kinetic of the adsorption, and the adsorption capacity of nano illite/smectite (I-Sm) clay was found to be 256.41 μg·g-1 for Pb(II). The adsorption patterns followed the Langmuir isotherm model. Thermodynamic parameters, including the Gibbs free energy (DG), enthalpy (DH), and entropy (DS) changes, indicated that the present adsorption process was feasible, spontaneous, and endothermic in the temperature range of 298-333 K. [ABSTRACT FROM AUTHOR]

Background and Objectives: Increasing waste tiers production has made the recycling of this solid waste a critical issue in the world. On the other hand, it seems contamination of groundwater to the petroleum pollutant like gasoline is a great threat to the health of societies in developing countries. The main objective of this study was gasoline removal from aquatic environment by waste tire derived activated carbon. Materials and Methods: In this study for preparation of activated carbon from waste tires, KOH was used for chemical activation process. We used argon gas to prevent precursor oxidation . We applied N2 gas and BET isotherm for characterization of the prepared activated carbon texture. Isothermal and kinetic models were used for defining gasoline adsorption characteristic to adsorbent, and thermodynamic studies were used to determine the effect of temperature. Results: Characterization results revealed that SBET and VTOTAL were 111.702m2/g and 0.124cc/g respectively. Langmuir and pseudo-second order models were the best isotherm and kinetic models for prediction of the adsorbent behaviors to adsorb gasoline. The Gibbs free energy changes were negative at all temperatures applied. Conclusion: Produced activated carbon has desired surface area and adsorptive capacity for gasoline adsorption in aquatic environments and it seems preparation activated carbon from waste tiers is cheap, effective and environment friendly.

Illite-smectite clay is a new mixed mineral of illite and montmorillonite. The ability of nano illite/smectite clay to remove Pb(II) from slightly polluted aqueous solutions has been investigated. The effects of pH, contact time, initial concentration of Pb(II), nano illite/smectite clay dosage, and temperature on the adsorption process were studied. The nano illite/smectite clay was characterized by X-Ray Diffraction (XRD), Fourier transform infrared spectrometry (FTIR), and Scanning electron microscopy (SEM). The results showed that Pb(II) was adsorbed efficiently by nano illite/smectite clay in aqueous solution. The pseudo-second-order kinetic model best described the kinetic of the adsorption, and the adsorption capacity of nano illite/smectite (I-Sm) clay was found to be 256.41 μg·g−1 for Pb(II). The adsorption patterns followed the Langmuir isotherm model. Thermodynamic parameters, including the Gibbs free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) changes, indicated that the present adsorption process was feasible, spontaneous, and endothermic in the temperature range of 298–333 K.

A novel method of adsorption of Au(I) from cyanide leaching solution with weak alkaline anion exchange fibre (WAAEF) was studied here. The thermodynamics of Au(I) from cyanide leaching solution by the WAAEF from 288 K to 308K have been investigated. Langmuir, Freundlich and Temkin models were adopted and the results confirmed that the Freundlich model fitted best with the equilibrium data. Thermodynamic calculation indicated that the absorption of Au(I) from cyanide leaching solution by WAAEF was an endothermic process with increased entropy. In the dynamic adsorption process, the optimal operational conditions,i.e. flow rate 670.0 BV⋅h−1, loading density 0.211 g⋅cm−3and pH value 8.89 of the original solution, were obtained. Dynamic analytical analysis depicted that the elution yield could exceed up to 97% using a mixture of 3% H2SO4and 8% (NH2)2CS solution at a flow rate of 100.5 BV⋅h−1. [ABSTRACT FROM AUTHOR]

Gas-phase mercury capture performance of raw activated carbon (R-AC) and bromine modified activated carbon (AC–Br) was evaluated in a fixed-bed reactor. Effect of flue gas temperature on mercury adsorption efficiency was explored. Sorbent characterization was conducted to feature their morphologies correlated to mercury adsorption efficiency. Adsorption kinetic and thermodynamic analysis of fixed-bed experimental results was also carried out to explore the different mercury adsorption mechanisms of R-AC and AC–Br. The results show that vapor mercury adsorption capacity of AC–Br increases with temperature, but R-AC demonstrates opposite results. The bromine ion (Br − ) remains in the mesopore and the surface of R-AC in the form of amorphous during modification process, leading to the reduction of mesopore volume and the increase of micropore volume. The increase of active site (Br − ) on activated carbon improves chemisorption of vapor mercury on AC–Br at 150 °C and 200 °C. The kinetic analysis shows that mercury adsorption on active sites is the adsorption rate controlling step, in which it can be divided into two steps: surface adsorption and intraparticle diffusion adsorption. Vapor mercury adsorption on AC–Br needs more activated energy due to the enhancement of chemisorption. The initial mercury adsorption rate of AC–Br increases with temperature, which is different from that of R-AC. The thermodynamic analysis shows that the adsorption of gas-phase mercury on both R-AC and AC–Br is spontaneous, endothermic and mainly physical in nature enhanced by chemisorption. The bromine modification enhances chemisorption of vapor mercury on AC–Br leading to the increase of complexity degree of mercury adsorption process. [ABSTRACT FROM AUTHOR]

Magnetic vinylphenyl boronic acid microparticles, poly(ethylene glycol dimethacrylate(EG)–vinylphenyl boronic acid(VPBA)) [ m -poly(EG–VPBA)], produced by suspension polymerization and characterized, was found to be an efficient solid polymer for Cr(VI) adsorption. The m -poly(EG–VPBA) microparticles were prepared by copolymerizing of ethylene glycol dimethylacrylate (EG) with 4-vinyl phenyl boronic acid (VPBA). The m -poly(EG–VPBA) microparticles were characterized by N 2 adsorption/desorption isotherms, electron spin resonance (ESR), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), elemental analysis, scanning electron microscope (SEM) and swelling studies. The m -poly(EG–VPBA) microparticles were used at adsorbent/Cr(VI) ion ratios. The influence of pH, Cr(VI) initial concentration, temperature of the removal process was investigated. The maximum removal of Cr(VI) was observed at pH 2. Langmuir isotherm and Dubinin–Radushkvich isotherm were found to better fit the experiment data rather than Fruendlich isotherm. The kinetics of the adsorption process of Cr(VI) on the m -poly(EG–VPBA) microparticles were investigated using the pseudo first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models, results showed that the pseudo-second order equation model provided the best correlation with the experimental results. The thermodynamic parameters (free energy change, Δ G 0 enthalpy change, Δ H 0 ; and entropy change, Δ S 0 ) for the adsorption have been evaluated. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Fe3O4/MgAl-LDH composite with good superparamagnetism was prepared. [•] The magnetic composite adsorbed three red dyes from aqueous solution effectively. [•] The adsorption kinetics, isotherm, thermodynamic and mechanisms were discussed. [•] The composite was quickly separated by magnet before and after adsorption process. [ABSTRACT FROM AUTHOR]

Poly(ethylene glycol dimethacrylate-N-methacryloyl-(L)-tryptophan) [poly(EGDMA-MATrp)] microspheres containing L-tryptophan (average diameter=106-300 μm) were synthesized and characterized; their use as adsorbents in removal of Cr(VI) from aqueous solutions was investigated. The poly(EGDMA-MATRP) microspheres were prepared by copolymerizing of ethylene glycol dimethacrylate (EGDMA) with N-methacryloyl-(L)-tryptophan methyl ester (MATrp). The poly(EGDMA-MATrp) microspheres were characterized by N2 adsorption-desorption isotherms, elemental analysis, scanning electron microscope, and swelling studies. At fixed solid/solution ratio, various factors affecting the adsorption of Cr(VI) ions from aqueous solutions, such as pH, initial concentration, contact time, and temperature, were analyzed. Cr(VI) adsroption kinetic data followed pseudo-second-order kinetics. Experimental isotherms of Cr(VI) ions were successfully fit to both the Langmuir and the Dubinin-Radushkevich isotherm models. Thermodynamic aspects of the adsorption process, such as Gibbs free energy, enthalpy, and entropy changes, were investigated. [ABSTRACT FROM AUTHOR]

Background and Objectives: Increasing waste tiers production has made the recycling of this solid waste a critical issue in the world. On the other hand, it seems contamination of groundwater to the petroleum pollutant like gasoline is a great threat to the health of societies in developing countries. The main objective of this study was gasoline removal from aquatic environment by waste tire derived activated carbon. Materials and Methods: In this study for preparation of activated carbon from waste tires, KOH was used for chemical activation process. We used argon gas to prevent precursor oxidation . We applied N2 gas and BET isotherm for characterization of the prepared activated carbon texture. Isothermal and kinetic models were used for defining gasoline adsorption characteristic to adsorbent, and thermodynamic studies were used to determine the effect of temperature. Results: Characterization results revealed that SBET and VTOTAL were 111.702m2/g and 0.124cc/g respectively. Langmuir and pseudo-second order models were the best isotherm and kinetic models for prediction of the adsorbent behaviors to adsorb gasoline. The Gibbs free energy changes were negative at all temperatures applied. Conclusion: Produced activated carbon has desired surface area and adsorptive capacity for gasoline adsorption in aquatic environments and it seems preparation activated carbon from waste tiers is cheap, effective and environment friendly. [ABSTRACT FROM AUTHOR]

Cadmium is a toxic metal widely used in industry and it enters the environment from electroplating, smelting, alloy manufacturing, pigments, plastics, cadmium-nickel batteries, fertilizers, pesticides, mining, pigments and dyes, textile operations, and refining industries. Considering the harmful effects of cadmium, it is necessary to remove cadmium from liquid wastes at least to the limit accepted by regulations. The present study describes removal of cadmium from aqueous solutions using bacteria-modified red mud waste material. Batch adsorption experiments have been performed as a function of pH, contact time, temperature, and adsorbent dosage. The optimum results were obtained at pH 4.0, contact time of 60 min, temperature of 30°C, and an adsorbent dose of 1 mg/mL. The adsorption data was correlated with Langmuir and Freundlich adsorption models. The maximum adsorption capacity obtained from Langmuir adsorption model was 83.034 mg/g. The kinetic processes of cadmium adsorption on bacteria-modified red mud were described by applying pseudo- first-order and pseudo-second-order rate equations. The kinetic data for the adsorption process obeyed pseudo-second-order rate equations. Various thermodynamic parameters, such as ΔG°, ΔH°, and ΔS° were calculated and the negative value of ΔG° obtained indicate that the process was spontaneous, and the positive value of ΔH° confirms the reaction to be endothermic, and the positive value of ΔS° shows that the decrease in the degree of freedom of the adsorbed species. The bacteria-modified red mud investigated in this study exhibited a high potential for the removal of cadmium from aqueous solutions. [ABSTRACT FROM AUTHOR]

Abstract: Desalination, other than the natural water cycle, is hailed as the panacea to alleviate the problems of fresh water shortage in many water stressed countries. However, the main drawback of conventional desalination methods is that they are energy intensive. In many instances, they consumed electricity, chemicals for pre- and post-treatment of water. For each kWh of energy consumed, there is an unavoidable emission of Carbon Dioxide (CO2) at the power stations as well as the discharge of chemically-laden brine into the environment. Thus, there is a motivation to find new direction or methods of desalination that consumed less chemicals, thermal energy and electricity. This paper describes an emerging and yet low cost method of desalination that employs only low-temperature waste heat, which is available in abundance from either the renewable energy sources or exhaust of industrial processes. With only one heat input, the Adsorption Desalination (AD) cycle produces two useful effects, i.e., high grade potable water and cooling. In this article, a brief literature review, the theoretical framework for adsorption thermodynamics, a lumped-parameter model and the experimental tests for a wide range of operational conditions on the basic and the hybrid AD cycles are discussed. Predictions from the model are validated with measured performances from two pilot plants, i.e., a basic AD and the advanced AD cycles. The energetic efficiency of AD cycles has been compared against the conventional desalination methods. Owing to the unique features of AD cycle, i.e., the simultaneous production of dual useful effects, it is proposed that the life cycle cost (LCC) of AD is evaluated against the LCC of combined machines that are needed to deliver the same quantities of useful effects using a unified unit of $/MWh. In closing, an ideal desalination system with zero emission of CO2 is presented where geo-thermal heat is employed for powering a temperature-cascaded cogeneration plant. [Copyright &y& Elsevier]

Abstract: Effect of the granulation process onto the thermodynamic and kinetic sorption parameters of two basic dyes (Basic Yellow 28-BY 28 and Basic Green 4-BG 4) was evaluated in the present work. The charge surface properties of the surfactant-modified aluminium-pillared clay (CTAB-Al-Mont-PILC) particles were not modified, and the isoelectric point remains constant after high shear wet granulation. The Gibbs free energy of both BY 28 and BG 4 sorption was negative and decreased with the granulation; the endothermic nature of the sorption process was confirmed by the positive values of ΔH°. Adsorption kinetics of the two dyes, studied at pH 6 and 150mgL−1, follow the pseudo-first order kinetic model with observed rate constants of 2.5–4.2×10−2 min−1. The intraparticle diffusion model, proposed by Weber and Morris, was applied, and the intraparticle plots revealed three distinct sections representing external mass transfer, intraparticle diffusion and adsorption/desorption equilibrium. Diffusion coefficients, calculated from the Boyd kinetic equation, increased with the granulation and the particle size. Pseudo-first order kinetic constants, intraparticle diffusion rate constants and diffusion coefficients were determined for two other initial concentrations (50 and 100mgL−1) and include in a statistical study to evaluate the impact of granulation and initial concentration on the kinetic parameters. Kruskal–Wallis tests, Spearman’s rank order correlation and factor analysis revealed a correlation between (i) the diffusion coefficients and granulation, and between (ii) the intraparticle diffusion rate constants and initial concentration. [Copyright &y& Elsevier]

A modified suspension polymerization was used for the preparation of the mesoporous magnetic-poly(divinylbenzene-co-vinylimidazole) (m-poly(DVB-VIM)) microbeads in size 53-212 [an of average diameter. The specific surface area and the DVB/VIM mol ratio of the microspheres were determined as 29.47 m²/g and 1:4 mol/mol with Fe3O4, respectively. The physicochemical studies of adsorption of Ni(II) ions from aqueous solutions such as pH, initial concentration, amount of mesoporous m-poly(DVB-VIM) microbeads, contact time, and temperature onto the m-poly(DVB-VIM) microspheres were carried out. The maximum adsorption capacities of the m-poly(DVB-VIM) microspheres towards Ni(II) ions were determined as 13.51, 20.14, 21.00 and 23.62 mg/g at 277 K, 298 K, 318 K, and 338 K, respectively. The dynamic and equilibrium adsorption behaviours of the system were adequately described by the pseudo-second-order kinetic and the Langmuir isotherm models, respectively. Various thermodynamic parameters, such as the Gibbs' free energy change (ΔG°), the standard enthalpy change (ΔH°) and the standard entropy change (ΔS°) were also determined. Morever, after use in the adsorption, the m-poly(DVB-VIM) microbeads with paramagnetic property was separated from the via the applied magnetic force. These results indicate that the material studied could be used as a purifier for the removal of Ni(II) ions from water and wastewater under magnetic field. [ABSTRACT FROM AUTHOR]

The magnetic-poly(divinylbenzene-1-vinylimidazole) [m-poly(DVB-VIM)] microbeads (average diameter 53-212 μm) were synthesized and characterized; their use as adsorbent in removal of Cr(VI) ions from aqueous solutions was investigated. The m-poly(DVB-VIM) microbeads were prepared by copolymerizing of divinylbenzene (DVB) with 1-vinylimidazole (VIM). The m-poly(DVB-VIM) microbeads were characterized by N adsorption/desorption isotherms, ESR, elemental analysis, scanning electron microscope (SEM) and swelling studies. At fixed solid/solution ratio the various factors affecting adsorption of Cr(VI) ions from aqueous solutions such as pH, initial concentration, contact time and temperature were analyzed. Langmuir, Freundlich and Dubinin-Radushkvich isotherms were used as the model adsorption equilibrium data. Langmuir isotherm model was the most adequate. The pseudo-first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models were used to describe the adsorption kinetics. The apparent activation energy was found to be 5.024 kJ mol, which is characteristic of a chemically controlled reaction. The experimental data fitted to pseudo-second-order kinetic. The study of temperature effect was quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy and entropy changes. The thermodynamic parameters obtained indicated the endothermic nature of adsorption of Cr(VI) ions. Morever, after the use in adsorption, the m-poly(DVB-VIM) microbeads with paramagnetic property were separeted via the applied magnetic force. The magnetic beads could be desorbed up to about 97% by treating with 1.0 M NaOH. These features make the m-poly(DVB-VIM) microbeads a potential candidate for support of Cr(VI) ions removal under magnetic field. [ABSTRACT FROM AUTHOR]

This study is aimed at the synthesis and characterization of the mesoporous magnetic-poly(divinylbenzene-1-vinylimidazole)[m-poly(DVB-VIM))microbeads(average diameter = 53–212 µm); their application as adsorbent in the removal of Cu(II) ions from aqueous solutions was investigated. The mesoporous m-poly(DVB-VIM) microbeads were prepared by copolymerizing of divinylbenzene (DVB) with 1-vinylimidazole (VIM). The mesoporous m-poly(DVB-VIM) microbeads were characterized by N2 adsorption/desorption isotherms, ESR, elemental analysis, scanning electron microscope (SEM), and swelling studies. At fixed solid/solution ratio the various factors affecting adsorption of Cu(II) ions from aqueous solutions such as pH, initial concentration, amount of mesoporousm-poly(DVB-VIM)) microbeads, contact time, and temperature were analyzed. Langmuir, Freundlich, and Dubinin-Radushkvich isotherms were used the model adsorption equilibrium data. The Langmuir isotherm model was the most adequate. The pseudo first-order, pseudo-second-order, Ritch-second-order, and intraparticle diffusion models were used to describe the adsorption kinetics. The experimental data fitted to pseudo second-order kinetic. The study of temperature effect was quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy changes. Morever, after the use in adsorption, the mesoporous m-poly(DVB-VIM) microbeads with paramagnetic property was separated via the applied magnetic force. These features make the mesoporous m-poly(DVB-VIM) microbeads a potential candidate for support of Cu(II) ions removal under magnetic field. [ABSTRACT FROM PUBLISHER]

Abstract: The feasibility of chitosan and cross-linked chitosan beads as efficient adsorbents for the removal of Acid Blue 25 (AB 25) and Acid Red 37 (AR 37) from aqueous solution was studied by using batch adsorption techniques. Glutaraldehyde (GLA) and sulphuric acid were employed as cross-linking reagents. The effect of process parameters like pH, agitation period, agitation rate and concentrations of dyes on the extent of AR 37 and AB 25 adsorption by chitosan and cross-linked chitosan beads was investigated. The best interpretation for the equilibrium data was given by the Langmuir isotherm, while the pseudo-second-order kinetic model could best describe the adsorption of these acid dyes. Thermodynamic parameters such as enthalpy change (ΔH°), free energy change (ΔG°) and entropy change (ΔS°) were estimated and adsorption process was spontaneous and exothermic. The desorbed chitosan, chitosan–GLA and chitosan–H2SO4 beads can be reused to adsorb the acid dyes. Results also showed that chitosan, chitosan–GLA and chitosan–H2SO4 beads were favourable adsorbers. [Copyright &y& Elsevier]