Solute Adsorption Research Articles

Adsorption of Methyl Red and Methylene Blue on Carbon Bioadsorbents Obtained from Biogas Plant Waste Materials.

In this study, biocarbon was obtained from the waste material corn digest. Carbon adsorbents were obtained by physical activation of the precursor with CO2. Detailed physicochemical characterization of the biocarbon was carried out using low-temperature nitrogen adsorption/desorption, Boehm titration, zero-charge point (pHpzc) and iodine number. In addition, the sorption capacity of the biocarbon agents towards an aqueous solution of methylene blue and methyl red was determined, and the kinetics of the adsorption process were determined. The biocarbon adsorbents were characterized by an average developed specific surface area covering the range from 320 to 616 m2/g. The sorption capacity of the biocarbon adsorbents against methylene blue ranged from 40 mg/g to 146 mg/g, and for methyl red it covered the range from 31 mg/g to 113 mg/g. It was shown that the efficiency of organic dye removal by the obtained biocarbons depends on the initial concentration of the adsorbate solution, its mass, shaking rate, adsorbent-adsorbate contact time and temperature. The results obtained from the Langmuir and Freundlich kinetic models showed that the Langmuir model is the most suitable model for describing the adsorption of the studied pollutants on biocarbon. In turn, the adsorption kinetics of dyes is described according to the pseudo-second-order model. Adsorption studies also showed that as the process temperature increases, the removal efficiency of methylene blue and methyl red increases.

Abalone shell-based magnetic macroporous hydroxyapatite microspheres with good reusability for efficient dye adsorption

Azo dye methyl orange (MO) and shell rotting cause great environmental pollution. Most of the common dye adsorbents are difficult to produce, not environmentally friendly and it is always difficult to utilize the shell resources effectively. In this study, shell-based economical and environmentally friendly magnetic hydroxyapatite microsphere adsorbents (Fe3O4 @SiO2/HAP) were developed for the removal of MO from simulated wastewater by sol-gel and hydrothermal synthesis methods. The effects of solution pH, initial concentration, adsorption time and system temperature on the adsorption effect were investigated, and the repeat recovery performance was explored. The equilibrium adsorption data follow the Freundlich isotherm and pseudo-second-order kinetic curves, and the analysis indicates that the adsorption process is spontaneously exothermic. The adsorption capacities of MO were up to 94.48% and 88.94%, under the acidic environment of pH = 4, respectively, and had good recycling performance. The results provide a high-value utilization pathway for waste shell resources and focus on the removal of azo dyes. This is expected to provide new development ideas for the environmental hazards caused by acid dye wastewater discharged into rivers and oceans, as well as the problems of soil pollution and resource waste caused by weathering and corrosion of shells.

Synthesis and characterization of the sea urchin-like γ-AlOOH/Fe3O4@SiO2 nanosorbent with ultra-high performance of Congo red removal

To manifest the benefits of nanosorbents in microstructure, the strong magnetism of Fe3O4 nanospheres is fully utilized to realize the rapid solid–liquid separation of adsorbent and aqueous solution. A sea urchin-like magnetic composite nanosorbent with a hierarchical structure was successfully manufactured by a simple and efficient liquid-phase hydrothermal synthesis method. Furthermore, its graded structure can sufficiently enhance the porosity and Zeta potential value of the material to increase the adsorption site and adsorption force between the material and CR molecular. The synthesized nanosorbent was then explored by a series of material physical and chemical characterization tools. It can be illustrated that the adsorbent is a strong magnetic composite nanomaterial with uniform particle size distribution and high dispersion, and is based on Fe3O4@SiO2 smooth nanoparticles as the inner core and γ-AlOOH as the shell. The saturation adsorption capacity reached 4534.57 mg g−1 with due expedition (under the adsorbent mass of 50 mg, CR mass concentration of 1500 mg/L, temperature of 25 °C and solution pH value of 3), whereas the γ-AlOOH of 925.34 mg g−1, Fe3O4 of 41.25 mg g−1 and Fe3O4@SiO2 of 93.21 mg g−1. After eight cycles of adsorption tests, the saturation capacity could still maintain 94.46% of the original adsorption capacity. Moreover, the adsorbent could be recovered by a simple applied magnetic field and the whole adsorption process conforms to the Pseudo-second kinetic model and the Langmuir isotherm model. Therefore, the sea urchin-like magnetic composite nanomaterials with a graded structure synthesized in this study could be widely utilized as a potential adsorbent material for CR removal.

A comparative study of electrodeposition and sodium dithionite reduction for recovering gold in gold-rich solution from the adsorption of thiosulfate solution by ion exchange resin

A comparative study was performed on electrodeposition and sodium dithionite reduction for recovering gold in the gold-rich solution from the adsorption of thiosulfate solution by ion exchange resin. Using electrodeposition method, gold started to deposit when the potential was lower than −100 mVHg/HgO. The rise of Cl− concentration improved gold deposition while the increases of SO32− and S2O32− concentrations were unbeneficial to gold deposition. When the solution was deposited at the optimum potential of −600 mVHg/HgO for 5 h, the gold deposition percentage reached 99.33 %. With sodium dithionite reduction method, the gold reduction percentage achieved 100 % after only 5 min as S2O42− dosage was eight times of the theoretical amount. The increases of SO32− and S2O32− concentrations hindered gold reduction while the augment of Cl− concentration had no obvious effect. Overall, sodium dithionite reduction method has the advantages of shorter reaction time, higher gold recovery percentage, better solution stability and lower recovery cost, and thus it has a broader industrial application prospect.

Magnetic Adsorbent Fe3O4/ZnO/LC for the Removal of Tetracycline and Congo Red from Aqueous Solution.

Zeolitic imidazolate frameworks (ZIFs) can be used as an adsorbent to efficiently adsorb organic pollutants. However, ZIF nanoparticles are easy to form aggregates, hampering the effective and practical application in practical adsorption. In this study, the ZIF-8 was successfully loaded onto lignocellulose (LC) to further produce ZnO/LC by in situ growth method and hydrothermal treatment, and then Fe3O4 nanoparticles (Fe3O4 NPs) were loaded onto ZnO/LC to prepare magnetic Fe3O4/ZnO/LC adsorbent for removing tetracycline (TC) and congo red (CR) pollutants from aqueous solution. The adsorption properties of the adsorbent were systematically analyzed for different conditions, such as adsorbent dosage, solution pH, contact time, temperature and initial concentration. The experimental data were fitted using adsorption kinetic and isotherm models. The results showed that the pseudo-second-order model and Sips model were well fitted to the adsorption kinetic and adsorption isotherm, respectively. The adsorption capacities of TC and CR reached the maximum value of 383.4 mg/g and 409.1 mg/g in experimental conditions. The mechanism of the removal mainly includes electrostatic interaction, hydrogen bonding and π-π stacking. This novel adsorbent could be rapidly separated from the aqueous solution, suggesting its high potential to remove pollutants in wastewater.

Facile Synthesis of Catechol-Containing Polyacrylamide Copolymers: Synergistic Effects of Amine, Amide and Catechol Residues in Mussel-Inspired Adhesives.

The straightforward synthesis of polyamide-derived statistical copolymers with catechol, amine, amide and hydroxy residues via free radical polymerization is presented. In particular, catechol, amine and amide residues are present in natural mussel foot proteins, enabling strong underwater adhesion due to synergistic effects where cationic residues displace hydration and ion layers, followed by strong short-rang hydrogen bonding between the catechol or primary amides and SiO2 surfaces. The present study is aimed at investigating whether such synergistic effects also exist for statistical copolymer systems that lack the sequence-defined positioning of functional groups in mussel foot proteins. A series of copolymers is established and the adsorption in saline solutions on SiO2 is determined by quartz crystal microbalance measurements and ellipsometry. These studies confirm a synergy between cationic amine groups with catechol units and primary amide groups via an increased adsorptivity and increased polymer layer thicknesses. Therefore, the free radical polymerization of catechol, amine and amide monomers as shown here may lead to simplified mussel-inspired adhesives that can be prepared with the readily scalable methods required for large-scale applications.

Extended X-ray Absorption Fine Structure Revealed the Mechanism of Arsenate Removal by the Fe/Mn Oxide-Based Composite under Conditions of Fully Saturated Sorption Sites.

Molecular mechanism of arsenate removal by a promising inorganic composite based on Fe/Mn oxides and MnCO3 was studied under the rarely investigated conditions of fully saturated sorption sites (characteristic of dynamic sorption, such as water treatment plants) at the pH of 4/6/7/8 using As K-edge extended X-ray absorption fine structure (EXAFS)/X-ray absorption near-edge structure (XANES), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR). Comparison of arsenic speciation in the initial adsorbate solution (calculated by Visual MINTEQ) and after sorption (determined by As 3d XPS) allowed the interpretation of the initializing forces of the interfacial processes. Contribution of various solid phases of this composite anion exchanger to the removal of arsenate was disclosed by examining the Fe 2p3/2 and Mn 2p3/2 XPS spectra supported by FTIR. As K-edge EXAFS simulation not only proved the chemisorptive binding of aqueous As(V) anions to the Fe/Mn oxide-based adsorbent but also demonstrated the presence of a variety of sorption sites in this complex structured porous material, which became available step-wise upon an increasing pressure on the interface with high arsenate loading during the long-term sorption process. The type of inner-sphere complexation of As(V) on the saturated surface discovered by As K-edge EXAFS modeling was a function of pH. Analysis of EXAFS fitting data resulted in suggestion of a methodological idea on how the EXAFS-derived coordination numbers can be used to distinguish the localization of adsorbed ions (surface versus structure emptiness). This work also provides more insights into the superiority of composite adsorbents (compared to the materials based on individual compounds) in terms of their capability to adapt/change the molecular sorption mechanism in order to inactivate (remove) more toxic aqueous anions.

Ultrahigh adsorption capacity of a new metal sieve-like structure nanocomposite-based chitosan-graphene oxide nanosheet coated with poly-o-toluidine for the removal of Acid Red dye from the aquatic environment

This article describes an easy and simple method to remove a toxic Acid Red dye from aqueous solution. Ternary poly(O-toluidine)/graphene oxide/chitosan P(OT)/GO/CS nanocomposites (NCs) were fabricated by an oxidative polymerization technique to remove Acid Red (A.R.) dye from aqueous solutions using solid-phase extraction. The P(OT)/GO/CS NCs exhibit a metal sieve-like structure consisting of GO nanosheets and a core shell-shell porous structure, which provides several adsorption sites and channels for the transport of dye molecules. FTIR, XRD, RAMAN, TEM, SEM, BET, and TGA-DTG investigations were carried out on NCs. To investigate the removal effectiveness of the NCs using adsorbent dose, pH and solution temperature, shaking time, and ionic strength. Experimental adsorption findings, utilizing 15 mg of solid-phase NCs, can remove the majority of the A.R. dye in 75 min at pH 2.0 with an adsorption efficiency and an adsorption capacity of 99.6% and 169.5 mg/g, respectively. The pseudo-second-order kinetic model best captures the adsorption process of A.R. dye on the NC solid phase, according to experimental data. Thermodynamically, the removal process was endothermic, spontaneous, and associated with increasing randomness. Finally, NCs were tested by removing A.R. dye from real samples. NCs removed A.R. dye from aqueous solutions for four cycles.

Efficient simultaneous phosphate and ammonia adsorption using magnesium-modified biochar beads and their recovery performance

Phosphate and ammonia as important sources of eutrophication in water bodies, their removal and recovery are crucial for environmental management. In this study, magnesium-modified biochar beads (Ca/MgBC) capable of adsorbing PO3–4 and NH+4 simultaneously were prepared, the size of the biochar materials was successfully enlarged to realize recycling. Ca/MgBC has excellent simultaneous adsorption properties, compared to single PO3–4 or NH+4 solution, the adsorption capacity of PO3–4 was increased almost twice and that of NH+4 was increased almost 1.5 times in simultaneous adsorption solution. The Qmax,PO3–4 was 253.95 mg/g and Qmax, NH+4 was 177.25 mg/g. Characterization results indicated that struvite crystallization was the main adsorption mechanism of PO3–4 and NH+4 in the simultaneous solution, which was also the reason for the promotion effect of simultaneous adsorption. Besides, ion exchange, surface precipitation and electrostatic attraction were also the other mechanisms for the adsorption. NP-loaded Ca/MgBC has a better slow-release potential of N and P under neutral condition. The adsorbed saturated Ca/MgBC still had good removal effects on seven common soil heavy metals (Cd, Hg, Cu, Pb, Cr, Zn and Ni). These results suggest that Ca/MgBC is a kind of promising adsorbent for phosphate and ammonia with safe, green, and sustainable properties, and offers the possibility of soil fertilization and remediation for carbon neutrality.

Assessment of g‒Mg3N2 membrane performance for efficient removal of dioxane contaminant from wastewater: DFT‒MD simulation treatments

We implemented DFT calculations for gas phase and DFT‒MD simulations for ambient conditions to evaluate the efficient performance of g‒Mg3N2 monolayer in 1,4‒dioxane removal from wastewater. The geometries, interaction energies, and interaction nature of the adsorbed dioxane and H2O molecules on the Mg3N2 surface were investigated. It was found that the interaction of H2O exceeds that of dioxane by twelve though, the two adsorbates follow rather a similar trend in the adsorption process. The AIM analysis was carried out to investigate the nature of bonding for adsorbed dioxane/H2O on the Mg3N2 surface. Furthermore, DFT‒MD simulation shows that dioxane tends to adsorb on the Mg3N2 nanosheet in the presence of water molecules at ambient conditions, making the Mg3N2 potentially suitable adsorbent for dioxane adsorption in aqueous solution. This exploration presents a foundation for the capability of computational study for predicting the adsorption and remediation of organic contaminants from wastewater.

Coexisting ions and long-chain per- and polyfluoroalkyl substances (PFAS) inhibit the adsorption of short-chain PFAS by granular activated carbon

We assessed the competitive adsorption between long-chain and short-chain PFAS and the impact of coexisting ions to understand the mechanisms leading to the early breakthrough of short-chain PFAS from granular activated carbon (GAC) filters. Three pairs of short-chain and long-chain PFAS representing different functional groups were studied using GAC (Filtrasorb 400) in batch systems. In bisolute systems, the presence of long-chain PFAS decreased the adsorption of short-chain PFAS by 30–50% compared to their single solute adsorption capacity (0.22–0.31 mmol/g). In contrast to the partial decrease observed in bisolute systems, the addition of long-chain PFAS to GAC pre-equilibrated with short-chain PFAS completely desorbed all short-chain PFAS from GAC. This suggested that the outermost adsorption sites on GAC were preferentially occupied by short-chain PFAS in the absence of competition but were prone to displacement by long-chain PFAS. The presence of inorganic/organic ions inhibited the adsorption of short-chain PFAS (up to 60%) but had little to no impact on long-chain PFAS, with the inhibitory trend inversely correlated with Kow values. Study results indicated that the displacement of short-chain PFAS by long-chain PFAS and charge neutralization are important mechanisms contributing to the early breakthrough of short-chain PFAS from GAC systems.

The study of the removal of penconazole fungicide from surface water using carboxymethyl tragacanth-based hydrogel grafted with poly (acrylic acid-co-acrylamide)

In this study, a polymeric adsorbent based on carboxymethyl tragacanth (CMT) grafted by poly acrylic acid-co-acrylamide (AAc-co-AAm) synthesized by radical polymerization for the first time was used to remove the fungicide penconazole (PEN) or Topas 20% from surface water. The parameters of solution pH, adsorption isotherm, and adsorption kinetics of PEN were studied by the synthetic adsorbent. The surface morphology and functional groups of CMT-g-poly (AAc-co-AAm) were confirmed by XRD, SEM and FT-IR techniques. Adsorption of PEN on CMT-g-poly (AAc-co-AAm) follows the Freundlich and pseudo-second-order models. The significant maximum adsorption capacity of the synthesized polymer was found to be 196.08 mg/g. The synthetic adsorbent had good reproducibility in PEN removal for up to 5 cycles. CMT-g-poly (AAc-co-AAm) is a cost-effective and non-toxic adsorbent for the decontamination of surface water from pesticides.

Cerium(IV) chitosan-based hydrogel composite for efficient adsorptive removal of phosphates(V) from aqueous solutions

The excess presence of phosphate(V) ions in the biosphere is one of the most serious problems that negatively affect aqueous biocenosis. Thus, phosphates(V) separation is considered to be important for sustainable development. In the presented study, an original cerium(IV)-modified chitosan-based hydrogel (Ce-CTS) was developed using the chemical co-precipitation method and then used as an adsorbent for efficient removal of phosphate(V) ions from their aqueous solutions. From the scientific point of view, it represents a completely new physicochemical system. It was found that the adsorptive removal of phosphate(V) anions by the Ce-CTS adsorbent exceeded 98% efficiency which is ca. 4-times higher compared with the chitosan-based hydrogel without any modification (non-cross-linked CTS). The best result of the adsorption capacity of phosphates(V) on the Ce-CTS adsorbent, equal to 71.6 mg/g, was a result of adsorption from a solution with an initial phosphate(V) concentration 9.76 mg/dm3 and pH 7, an adsorbent dose of 1 g/dm3, temperature 20 °C. The equilibrium interphase distribution data for the Ce-CTS adsorbent and aqueous solution of phosphates(V) agreed with the theoretical Redlich-Peterson and Hill adsorption isotherm models. From the kinetic point of view, the pseudo-second-order model explained the phosphates(V) adsorption rate for Ce-CTS adsorbent the best. The specific effect of porous structure of adsorbent influencing the diffusional mass transfer resistances was identified using Weber-Morris kinetic model. The thermodynamic study showed that the process was exothermic and the adsorption ran spontaneously. Modification of CTS with cerium(IV) resulted in the significant enhancement of the chitosan properties towards both physical adsorption (an increase of the point of zero charge of adsorbent), and chemical adsorption (through the presence of Ce(IV) that demonstrates a chemical affinity for phosphate(V) anions). The elaborated and experimentally verified highly effective adsorbent can be successfully applied to uptake phosphates(V) from aqueous systems. The Ce-CTS adsorbent is stable in the conditions of the adsorption process, no changes in the adsorbent structure or leaching of the inorganic filling were observed.

Synchronous stabilization of Pb, Zn, Cd, and As in lead smelting slag by industrial solid waste

In order to prevent heavy metal (HM) pollution from lead smelting slag (LSS) to the surrounding environment, this work investigated the feasibility, influencing factors, and mechanisms of using industrial solid waste such as fly ash (FA), oil sludge pyrolysis residue (PR), and steel slag (SS) as remediation amendments. The results demonstrated that the stabilization process was influenced by the material dosage, water content, and LSS particle size. Compared to single materials, the combination amendment PR2FA1 (with a mass ratio of PR to FA as 2:1) exhibited the best stabilization effect, simultaneously reducing the leaching concentrations of As, Zn, Cd, and Pb in LSS to 0.032, 0.034, 0.002, and 0.014 mg/L, respectively. The pH value of the leachate remained between 8 and 9, which met the requirements of surface water quality class IV (GB3838–2002). Through morphological analysis, microscopic characterization, and simulated solution adsorption experiments, it was determined that the stabilization process of HMs was controlled by various mechanisms, including electrostatic attraction, physical adsorption, ion exchange, and chemical precipitation. PR2FA1 had more active components, and its fine-porous structure provided more active sites, resulting in good stabilization performance for As, Zn, Cd, and Pb. Furthermore, cost analysis showed that PR2FA1, as an environmentally friendly material, could generate profits of 157.2 ¥/ton. In conclusion, the prepared PR2FA1 not only addressed the HMs pollution from lead smelting slag to the surrounding environment but also achieved the safe and resourceful disposal of hazardous waste-oil sludge. Its excellent performance in stabilizing HMs and cost-effectiveness suggested promising commercial applications.

Elaboration of the new heterostructure of NiAl2O4/kaolin and its photocatalytic activity towards methyl green under solar light irradiation

Nanosized spinel NiAl2O4 was successfully supported on kaolin, natural support, by impregnation method; then tested as photocatalyst towards organic pollutant. The catalyst was characterized by IR spectroscopy, XR diffraction, BET, reflectance and XPS techniques. The photocatalytic tests were followed by UV-Vis spectroscopy for degradation of Methyl Green (MG) solution (C0=50 mg/L) under sunlight irradiation. The maximum adsorption (91.56 mg/g) of MG dye solution was observed for NiAl2O4 at an equilibrium time of 240 min; nevertheless, for NiAl2O4/kaolin, the equilibrium time was only 150 min for an adsorbed quantity equal to 45.78 mg/g. Some parameters influencing the dye adsorption were optimized. The fitting of the adsorption data for the Methyl green follows the Langmuir isotherm model. This new nanocomposite of NiAl2O4/kaolin exhibited excellent photocatalytic activity, which can degrade MG dye; mainly after adding the hole sensors (H2O2), within 90 min under sunlight irradiation.

Column studies on the removal of chromium, lead, and Arsenic (Cr6+, Pb+2, and As3+) ions using graphene coated iron oxide (GCIO) as efficient nanoadsorbents

The efficient graphene coated iron oxide (GCIO) nanoadsorbent was prepared for removal of various ions, viz., Cr(VI), Pb(II), and As(III), by coating graphene onto the iron oxide surfaces taken as a base material. The as-prepared nanoadsorbent was further characterized by several analytical techniques such as Fourier transform infrared (FTIR) spectroscopy, energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Raman spectroscopy, Differential scanning calorimetry (DSC), and Zeta-potential measurements, respectively. These techniques provided valuable information about the nanoadsorbent and confirmed the interactions between Cr6+, Pb2+, and As3+ ions and the nanoadsorbent. The effect of concentration of adsorbate solution, contact time between adsorbate–adsorbent, and flow rate of adsorbate were studied using a sensitive, simple, and selective spectrophotometric method that enabled quantification of Cr6+, Pb+2, and As3+ ions, respectively. Various modeling of breakthrough curves was applied for monitoring progress of the adsorption process and the results showed that the three metal ions followed second order kinetic model thus confirming that GCIO is an excellent, effective, and economic adsorbent.

Two metal-organic frameworks based on tetracarboxylic ligand exhibiting high performance for gas adsorption and separation

Developing porous materials for purification of acetylene is of great significance, but remains challenging. Currently, the use of metal-organic frameworks (MOFs) for gas adsorption separation has received substantial research interest. Herein, based on the tetracarboxylic acid ligand H4TPTA ([1,1':3′,1″-terphenyl]-4,4′,4″,6′-tetracarboxylic acid), two MOFs (ErTPTA and CdTPTA) constructed by trinuclear cluster secondly building units (SBUs) have been successfully synthesized. They are three dimensional (3D) framework with 1D rhomboid channels, demonstrating a (4,8)-connected scu network. A series of gas adsorption tests were performed and the both compounds exhibited outstanding gas selective adsorption performance. Accordingly, the ideal adsorption solution theory (IAST) is used to simulate the adsorption selectivity, the selectivity of CdTPTA for CO2/CH4 is 11.85 (0.5:0.5) and 17.02 (0.05:0.95), and for C2H2/CH4 is 11.81 (0.5:0.5); the selectivity of ErTPTA for C2H2/CO2 is 4.45 (0.5:0.5).

Atomistic modeling of Mg-Al-Zn solid–liquid interfacial free energy

In this study anisotropic solid–liquid interfacial energy, γ, of Mg-Al-Zn system is evaluated based on capillary fluctuation method. To investigate effects of temperature and solute compositions on γ, five simulation cases, Cases I-V, are designed and divided into two group, Group I consist of Cases I-III for evaluation on solute compositions, while Group II consist of Cases I, IV and V for evaluation on temperatures. Interfacial energy stiffness of six differently oriented interfaces is evaluated, average interfacial energy, γ0, and anisotropic parameters of the interfaces are obtained. This study determined melting point of Mg as 964 ± 5 K, which matches the standard value of 923 K. Evaluation on γ0, and γ in high symmetric orientations γBasal, γPrismaticIA and γPrismaticIIA suggests, for Cases I-V, lower γ0 values within 15.74–18.19 mJ/m2 compared with elemental Mg could be related with the insufficiency of selected interatomic potential to describe the solid–liquid interface, and relation of γBasal>γPrismaticIIA>γPrismaticIA was identified. Comparisons within Group I indicate the increase of relative average equilibrium composition, c¯i/c¯j, will improve solute adsorption of element i on interface, which causes γ0 , γBasal, γPrismaticIA and γPrismaticIIA to decrease. As for Group II, temperature increase will result in decline of γ0 , γBasal, γPrismaticIA and γPrismaticIIA, similar trend was found in Al-Sm alloy systems. Primary dendrite growth orientations for Cases I-V were determined as [0001], analysis shown increase in either temperature or c¯i/c¯j stabilize this preference further towards [0001].

Agricultural Solid Wastes Based Adsorbent Materials in the Remediation of Heavy Metal Ions from Water and Wastewater by Adsorption: A Review.

Adsorption has become the most popular and effective separation technique that is used across the water and wastewater treatment industries. However, the present research direction is focused on the development of various solid waste-based adsorbents as an alternative to costly commercial activated carbon adsorbents, which make the adsorptive separation process more effective, and on popularising the sustainable options for the remediation of pollutants. Therefore, there are a large number of reported results available on the application of raw or treated agricultural biomass-based alternatives as effective adsorbents for aqueous-phase heavy metal ion removal in batch adsorption studies. The goal of this review article was to provide a comprehensive compilation of scattered literature information and an up-to-date overview of the development of the current state of knowledge, based on various batch adsorption research papers that utilised a wide range of raw, modified, and treated agricultural solid waste biomass-based adsorbents for the adsorptive removal of aqueous-phase heavy metal ions. Metal ion pollution and its source, toxicity effects, and treatment technologies, mainly via adsorption, have been reviewed here in detail. Emphasis has been placed on the removal of heavy metal ions using a wide range of agricultural by-product-based adsorbents under various physicochemical process conditions. Information available in the literature on various important influential physicochemical process parameters, such as the metal concentration, agricultural solid waste adsorbent dose, solution pH, and solution temperature, and importantly, the adsorbent characteristics of metal ion removal, have been reviewed and critically analysed here. Finally, from the literature reviewed, future perspectives and conclusions were presented, and a few future research directions have been proposed.

Novel magnetic polyethersulfone-polyethyleneimine-based microbeads for removal of lead ions from water: Kinetics and thermodynamics

In this study, a novel magnetic microbead adsorbent (M−PES−PEI) was made using magnetic iron oxide (MNPs), polyethersulfone (PES), and polyethyleneimine (PEI)to remove the lead ions (Pb2+) from drinking water. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR) methods were used to analyze the M−PES−PEI microbeads. Adsorbent dosage (20 mg), contact time (90 min), and solution pH ∼ 5 as the effective parameters on experimental conditions were examined and 91% removal of Pb2+ was obtained using 50 mg of microbeads. Adsorption models based on isotherms, kinetics, and thermodynamics were used to simulate the adsorption of Pb2+ over M−PES−PEI. The pseudo-second-order as the kinetic model was fitted to the adsorption data at different times (R2 > 0.97). In the isotherm study, the Freundlich model shows a higher R2 (0.99) value than the Langmuir model at different concentrations. After 90 min of contact time at room temperature, the maximum adsorption capacity was 312 mg.g−1 with physical mechanism.