Desorption Agent Research Articles

Influence of organic dispersant on nuclear grade anion exchange resin and their interaction behavior

ABSTRACT Polyacrylic acid (PAA) was used as an organic dispersant in the secondary circuit of nuclear power plants, which could interact with anion exchange resin and affect its properties in the condensate polishing treatment system. This study investigated the kinetics, isotherms, and thermodynamics characteristics of PAA adsorption on anion exchange resin. The results suggested that the inhibition of PAA adsorption on resin can be achieved by lowering the PAA concentration and temperature. In addition, the adsorption reversibility and influence of PAA on anion exchange resin were discussed. The chemical desorption agent (NaOH) can desorb 94.10% of the adsorbed PAA on resin. The physicochemical properties of anion exchange resin changed little after adsorbing and desorbing PAA. Furthermore, the interaction feature between PAA and anion exchange resin was revealed through analyzing the stoichiometry and ATR-FTIR spectra, which was partial ion exchange and most attachment. This feature caused the weak binding force between PAA and resin. Therefore, PAA was easily desorbed from the resin and the exchange capacity of resin can be restored after the chemical desorption process. In conclusion, PAA had little influence on the properties of anion exchange resin and did not cause nonreversible organic fouling.

Investigation of Thermodynamic, Kinetic, and Isothermal Parameters for the Selective Adsorption of Bisphenol A.

Herein, a novel imprinted solid-phase extraction cartridge was fabricated to investigate the kinetic, thermodynamic, and isothermal parameters for the selective adsorption of Bisphenol A (BPA). The imprinted polymeric cartridges (BMC) for the BPA adsorption were fabricated in the presence of a template and functional monomer using the in situ polymerization technique. To prove the efficiency and selectivity of BMC, the nonimprinted polymeric cartridges (BNC) and the empty polymeric cartridges (EC) were also fabricated with and without functional monomer using the same manner for the preparation of BMC. The characterization of cartridges was performed by elemental analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area measurements, and swelling tests. BPA removal studies were performed by analyzing some parameters such as temperature, BPA concentration, flow rate, salt type, and concentration. The highest capacity was determined as 103.2 mg BPA/g polymer for a 0.75 mL/min flow rate of 0.75 M (NH4)2SO4 containing 200 mg/L BPA solution at 50 °C. NaOH (1.0 M) was used as a desorption agent. The reusability performance was examined by performing 10 consecutive cycles. The solid-phase extraction (SPE) performance was also checked to determine the enrichment and extraction recovery factors for tap water and synthetic wastewater samples. Temkin, Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models were applied to BPA adsorption data examining the adsorption mechanism, surface properties, and adsorption degree. The most suitable isotherm model for BPA adsorption was determined as the Langmuir isotherm model. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were investigated to reveal the thermodynamics of adsorption. Adsorption thermodynamic parameters (ΔH°, ΔS°, and ΔG°) were calculated using the thermodynamic equilibrium constant (thermodynamic equilibrium constant, K°) values that change with temperature. It was determined that BPA adsorption was spontaneous (ΔG° < 0) and endothermic (ΔH° > 0) and entropy increased (ΔS° > 0) at the temperatures studied in the BPA adsorption process. The rate control step in the adsorption process was examined by applying pseudo-first-order and pseudo-second-order kinetic models to the adsorption data for the investigations of BPA adsorption kinetics, and the pseudo-second-order kinetic model was found to be more suitable for describing BPA adsorption kinetics. In examining the selectivity of cartridges, structural analogues of hydroquinone, phenol, β-estradiol, and 8-hydroxyquinoline were tested.

Rapid and selective recovery of Ag(I) from simulative electroplating effluents by sulfydryl-rich covalent organic framework (COF-SH) with high adsorption capacity

The aim of current work was to explore a new material for the fast, efficient and selective recovery of precious metal silver (Ag(I)) from electroplating effluents to alleviate its high consumption and mitigate its environmental pollution. In this study, the sulfydryl-rich covalent organic framework (COF-SH) was prepared by solvothermal method. Its Ag(I) adsorption performance was evaluated by batch adsorption experiments that the effects of initial Ag(I) concentration, ratio of adsorption dosage to solution volume, adsorption time and reacting temperature were studied. The isothermal data fitted well with the Langmuir model and the maximum adsorption capacity at 298 K was up to 609.89 mg/g. The adsorption rate was very fast almost achieving adsorption equilibrium within 16 min. The adsorption rate and adsorption capacity increased with the increase in reaction temperature. The perfect fitting with pseudo-second-order kinetic model indicated the adsorption process was dominated by chemisorption process. Weber–Morris intraparticle diffusion model divided the adsorption process into three stages and temperature had a positive correlation with the first stage, external surface diffusion. The thermodynamic fitting results suggested that the adsorption process was endothermic, disordered and spontaneous. In terms of application, COF-SH achieved highly selective adsorption of Ag(I) in simulated electroplating wastewater with coexistence of multiple metal ions, especially at high acidity (≥1 M HNO3), and the increase in concentration of competing ions had no affects. In addition, 1 M HNO3 + 0.3 M thiourea (TU) could be used as desorption agent with 100% Ag(I) desorbed from the adsorbed adsorbent COF-SH-Ag.

Performance of a synthetic resin for lithium adsorption in waste liquid of extracting aluminum from fly-ash

In this study, we investigated the performance of a synthetic resin for the adsorption of Li from pre-desilicated solution which is the waste liquid produced by extracting aluminum from fly ash. The adsorption kinetics and isotherms of the resin were obtained and analyzed. The saturated adsorption sites of the resin were in agreement with the quasi-second-order kinetic model. Then, the pore diffusion model (PDM) was applied to represent the lithium adsorption kinetics which confirming that the external mass is the limiting step. Moreover, we evaluated the adsorption properties of this resin in fixed-bed mode. We established a feasible extraction process for Li from strong alkaline solutions with low Li concentrations. The process parameters, such as the flow rate, initial adsorption solution concentration, water washing process, desorption agent concentration, and flow rate were studied. The desorption rate of the Li+ ions was directly proportional with the concentration of the desorption agent. The time required to accumulate Li decreased as the hydrochloric acid concentration and flow rate increased. Time of the peak appeared increased from 0.5 bed volume (BV) to 2.5 BV as the concentration was increased from 1 to 3 mol·L−1, and the peak increased from 231 to 394 mg·L−1. The resin presented good selectivity for Li+ ions and could effectively separate impurity ions from the pre-desilication solution.

Separation of palladium and silver from E-waste leachate: effect of nitric acid concentration on adsorption to Thiol scavenger

The development of recovery techniques for metals present in low concentrations in E-waste, such as silver and palladium, is important from the aspect of the circular economy. Adsorption of palladium and silver was studied in detail in a batch process with silica-based Thiol scavenger from nitric acid leachate of waste printed circuit boards (PCBs). High adsorption efficiencies of Pd(II) and Ag(I), >97%, were reached in nitric acid concentrations below 3 mol L−1. At higher acid concentrations, adsorption efficiency of Ag(I) decreased drastically which enables the separation of Ag(I) and Pd(II) based on nitric acid concentration in sample solution. Pd(II) and Ag(I) followed pseudo 2nd order kinetical model with fast adsorption with contact times of 60 and 30 min, respectively, in all studied acid concentrations. Adsorption followed Langmuir isotherm reaching highest loading capacities of 199 mg g−1 for Ag(I) and 105 mg g−1 for Pd(II) in 1 mol L−1 nitric acid media, after which loading capacities decreased while nitric acid concentration increased. Thiourea-based desorption agents were most effective for desorption with >80% desorption efficiencies for Ag(I) and 55 - 88% efficiencies for Pd(II) in a one-step desorption. However, separation of Pd(II) and Ag(I) is not entirely possible in desorption step, hence the highest separation between Pd(II) and Ag(I) was found with two-step adsorption in which Pd(II) and Ag(I) were separated initially at adsorption step based on nitric acid concentration, followed by desorption step with acidic thiourea solution.

The adsorption and desorption behavior and mechanism research of cobalt, nickel and copper in nitrite - sulfuric acid system

ABSTRACT In this paper, we studied the adsorption and desorption characteristics of cobalt, nickel, and copper in nitrite–sulfuric acid system, and their adsorption mechanism was also explored. The results showed that the adsorption capacity of cobalt and copper on the anion exchanger is 206 and 175 mg/g, respectively. However, the nickel adsorption capacity was very weak, exhibiting almost no adsorption. When the concentration of sodium nitrite was 1 mol/L, IRA-900 resin showed the best adsorption selectivity to cobalt. The FT-IR, UV absorption spectrometry, and XPS analysis results indicated that the adsorption mechanism of cobalt and copper could be attributed to the formation of anionic nitro-complexes in the solution, which could be exchanged with the anions on the resin to achieve the adsorption of metal ions. After a series of investigations, 1 mol/L sulfuric acid and ammonia were selected as desorption agents for cobalt and copper.

A Novel Combined Treatment Process of Hybrid Biosorbent–Nanofiltration for Effective Pb(II) Removal from Wastewater

The untreated effluents discharged by different industries, such as metallurgy, fertilizers, pesticide, leather, mining, electroplating, surface finishing, aerospace, and electroplating, have increased the risk of the contamination of bodies of water by heavy metals. Herein, hybrid biosorbent–nanofiltration processes for Pb(II) removal from wastewater was studied. The hybrid biosorbent was prepared from date seed waste and Ganoderma lucidum. Hybrid biosorbent characterization was performed by SEM and FTIR. SEM micrographs showed that the HB surface is irregular. For the adsorption studies, various sorption parameters were optimized. The maximum biosorption capacity of immobilized heat-inactivated hybrid biosorbent was 365.9 mg/g, with the Langmuir isotherm model to present the best fit. Desorption experiments were conducted for regenerating immobilized heat-inactivated hybrid biosorbent for three consecutive cycles using different desorption agents, with acetic acid to be the optimum. Going a step further, nanofiltration was also applied as a post-treatment process to elevate the remediation effectiveness for wastewater of high Pb(II) initial concentrations. The reasonably low cost and high removal of Pb(II) make hybrid biosorbent–nanofiltration processes a prosperous and potentially attractive hybrid approach against heavy-metal-polluted wastewater.

Adsorption of Cr(OH)n(3−n)+ (n = 1–3) on Illite (001) and (010) Surfaces: A DFT Study

The development of clay adsorption materials with high Cr(III) removal capacities requires an understanding of the adsorption mechanism at the atomic level. Herein, the mechanisms for the adsorption of Cr(OH)2+, Cr(OH)2+, and Cr(OH)3 on the (001) and (010) surfaces of illite were studied by analyzing the adsorption energies, adsorption configurations, charges, and state densities using density functional theory (DFT). The adsorption energies on the illite (010) and (001) surfaces decrease in the order: Cr(OH)2+ &gt; Cr(OH)2+ &gt; Cr(OH)3. In addition, the energies associated with adsorption on the (010) surface are greater than those on the (001) surface. Further, the hydrolysates are highly active and can provide adsorption sites for desorption agents. The silica (Si–O) ring on the illite (001) surface can capture Cr(OH)n(3−n)+ (n = 1–3). In addition, both Cr(OH)2+ and Cr(OH)2+ form one covalent bond between Cr and surface OS1 (Cr–OS1), whereas the hydroxyl groups of Cr(OH)3 form three hydrogen bonds with surface oxygens. However, increasing the number of hydroxyl groups in Cr(OH)n(3−n)+ weakens both the covalent and electrostatic interactions between the adsorbate and the (001) surface. In contrast, the Cr in all hydrolysates can form two covalent Cr–OSn (n = 1–2) bonds to the oxygens on the illite (010) surface, in which Cr s and O p orbitals contribute to the bonding process. However, covalent interactions between the cation and the (010) surface are weakened as the number of hydroxyl groups in Cr(OH)n(3−n)+ increases. These results suggest that the illite interlayer can be stripped to expose Si–O rings, thereby increasing the number of adsorption sites. Furthermore, regulating the generated Cr(III) hydrolysate can increase or weaken adsorption on the illite surface. Based on these findings, conditions can be determined for improving the adsorption capacities and optimizing the regeneration performance of clay mineral materials.

Experiments on continuous chemical desorption of CO2-rich solutions

The traditional thermal desorption is replaced by chemical desorption and the desorption tower is replaced by the reaction and precipitation tank to promote industrial application of chemical desorption. Monoethanolamine (MEA), N-methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP) and potassium glycine (PG) were selected and the effects of temperature, CO2 loading, dosage of desorption agent and different calcium compounds on the desorption ratio were studied. The results indicated that desorption ratios of MEA, MDEA, AMP and PG were enhanced with increasing temperature, but the desorption ratio had a maximum at 40 °C in the case of MDEA. With increases of CO2 loading and the amount of Ca(OH)2, desorption ratios increased. The desorption ratios of four CO2-rich solutions with CaO were lower than that of Ca(OH)2, but the difference in desorption ratio decreased as reaction time increased. The desorption ratios of MEA, MDEA, AMP and PG were able to reach 84.3%,90.17%,88.71% and 92.22% in optimum operating conditions, which were higher than that of conventional thermal desorption and the optimum operating conditions were as follows: the reaction temperature is 40 °C, CO2 loading is 0.21 mol/L, Ca:C is 1:1 and the desorption agent is Ca(OH)2. This study has crucial significance for the application of chemical desorption.

A Simple One-Step Modification of Shrimp Shell for the Efficient Adsorption and Desorption of Copper Ions.

Removing toxic heavy metal species from aqueous solutions is a point of concern in our society. In this paper, a promising biomass adsorbent, the modified waste shrimp shell (MS), for Cu (II) removal was successfully prepared using a facile and simple one-step modification, making it possible to achieve high-efficiency recycling of the waste NaOH solution as the modification agent. The outcome shows that with the continuous increase in pH, temperature and ion concentration, the adsorption effect of MS on Cu (II) can also be continuously improved. Adsorption isotherm and adsorption kinetics were fitted with the Langmuir isotherm model and the pseudo-second-order model, respectively, and the maximum adsorption capacity of Cu (II) as obtained from the Langmuir isotherm model fitting reached 1.04 mmol/g. The systematic desorption results indicated that the desorption rate of Cu (II) in the MS could reach 100% within 6 min, where HNO3 is used as the desorption agent. Moreover, experiments have proven that after five successive recycles of NaOH as a modifier, the adsorption capacity of MS on Cu (II) was efficient and stable, maintaining tendency in 0.83–0.85 mmol/g, which shows that waste NaOH solution can be used as a modification agent in the preparation of waste shrimp shell adsorbent, such as waste NaOH solution produced in industrial production, thereby making it possible to turn waste into renewable resources and providing a new way to recycle resources.

Development of ion imprinted based magnetic nanoparticles for selective removal of arsenic (III) and arsenic (V) from wastewater

ABSTRACT In this study, we fabricated magnetic ion-imprinted polymers (IIP) for arsenic removal. Ion-imprinted method was developed by complexing N-methacryloyl-l-cysteine (MAC) monomer and As(III) and As(V) as template molecules. The utilization of the MAC-As complex was chosen to provide a rebinding of As(III) and As(V) on IIP. The template molecules were removed by using 0.01 M HNO3 containing 0.05% thiourea solution as a desorption agent. The adsorption of As(III) and As(V) was ideal in buffer solution pH 5.0 for 120 min with removal capacity. The ion-imprinted-based magnetic nanoparticles were selective for arsenic toward other analogs (NO3 −, PO4 3-, SO4 2- as an anion, and AsO2 −, HAsO4 − as an oxi-anion). The adsorption isotherm model fitted the Langmuir model with an R2 value of 0.9935–0.9118 and the Qmax values of 91.7 mg/g for As(III)-IIP magnetic nanoparticles and 99.0 mg/g As(V)-IIP nanoparticles, respectively. Finally, IIP-based magnetic nanoparticle adsorbents have been utilized successfully for effective arsenic removal from wastewater samples.

Simultaneous removal of toxic Pb(II) ions, poly(acrylic acid) and Triton X-100 from their mixed solution using engineered biochars obtained from horsetail herb precursor – Impact of post-activation treatment

The horsetail herb was used as the precursor and was subjected to direct physical activation with steam (800 °C for 1 h). Next two variants of post-activation treatment was applied: (1) two-steps washing procedure, firstly with a hot 10% solution of HCl and later with demineralized water (HBA_HCl sample) and (2) one-step washing procedure only with demineralized water (HBA_H2O sample). The final products were characterized towards its textural structure, acid-base properties and surface morphology. The obtained biochars were used as adsorbents for simultaneous removal of hazardous lead(II) ions, poly(acrylic acid) (PAA) polymer and Triton X-100 nonionic surfactant from their mixed solution.It was shown that Pb(II) and PAA adsorbed amounts (from the single and mixed systems of adsorbates) have the greatest values on the HBA_HCl surface in the double PAA + Pb(II) system (148.8 mg/g and 195.8 mg/g, respectively) and in the triple PAA + TRT + Pb(II) system (183.3 mg/g and 187.7 mg/g, respectively). The nonionic surfactant desorption reaches high level (83–100%), independently from using desorption agent (HNO3 or NaOH). Generally in the case of PAA, NaOH solution turned out to be more effective in adsorbent recovery process (especially from HBA_H2O surface), whereas in the case of Pb(II) ions desorption, HNO3 is more effective desorbing agent (74–96% desorption).

Strategic study of adsorption and desorption of chromium on vertisols and its implication in developing an effective remediation technology

ABSTRACT Chrome tanning in India leads to severe contamination of soil and water. Due to the indiscriminate disposal of effluent from tanneries, several thousand hectares of agricultural lands have been degraded over several decades in Tamil Nadu. Several researchers were involved in developing remediation technologies for chromium contamination.Adsorption and desorption of Cr on soil determine the mobility of Cr and its environmental impact. There are several studies regarding the adsorption/desorption of Cr. A strategic study regarding the mechanism of adsorption/desorption of Cr to the context of remediation technologies is essential. A better understanding of the adsorption and desorption mechanism of Cr aids in developing a suitable remediation strategy. Therefore, in the present investigation, the adsorption Cr on soil and some critical factors affecting the adsorption were studied. The Cr adsorption on soil recorded maximum and was best illustrated by the Freundlich isotherm (R2 = 0.994) than the Langmuir isotherm (R2 = 0.841). Amongst the bio-amendments, biochar was found to enhance the adsorption of Cr on the soil. The co-contaminants such as cadmium and lead significantly reduced the adsorption of Cr. Further, a desorption study was carried out with different desorption agents such as NaOH, CH3COONH4and EDTA. It was found that NaOH exhibited higher desorption efficiency than the other agents. The results reveal that adsorption and desorption mechanisms aids in predicting the toxicity of Cr. This study also shows that the soil pH, bio-amendments, and co-contaminants in the contaminated soil may play a significant role in the remediation process.

Matrix Solid-Phase Dispersion Coupled with HPLC-UV for Simultaneous Extraction, Purification and Determination of Six Lignans in Schisandra chinensis Fruits.

An efficient method for simultaneous extraction, purification and determination of six lignans in Schisandra chinensis Baill was developed by employing matrix solid-phase dispersion (MSPD) extraction followed by HPLC-UV determination analysis. Several sorbent and desorption solvent that affected the extraction yield of lignans were investigated; neutral alumina and absolute ethanol were selected as the best dispersing material and desorption agent, respectively. Other extraction conditions for MSPD were optimized as follows: 1:2 of S. chinensis raw material to neutral aluminum oxide mass ratio, 1:30 (g/mL) of sample to absolute ethanol, 2.5h of desorption time and 50°C of desorption temperature. Under the above conditions, the total extraction yield for six lignans have reached (16.99±0.33) x 103 mg/kg with a higher content of 6.88±0.25% in the extracts. Comparative studies were explored by conducting other six extraction approaches including Soxhlet extraction, heat reflux extraction, smashing tissue extraction, microwave-assisted extraction, ultrasonic-assisted extraction and ultrasonic-microwave synergistic extraction. Results showed MSPD technique not only improved the extraction yield, but also improved the purity of lignans, it can be generalized to more extraction of natural compounds. In addition, the validated HPLC-UV method had been successfully applied to analysis of lignans from 10 real S. chinensis samples.

Phosphate removal by a La(OH)3 loaded magnetic MAPTAC-based cationic hydrogel: Enhanced surface charge density and Donnan membrane effect

Cationic hydrogels have received great attention to control eutrophication and recycle phosphate. In this study, a type of La(OH)3 loaded magnetic MAPTAC-based cationic hydrogel (La(OH)3@MMCH) was developed as a potential adsorbent for enhanced phosphate removal from aqueous environment. La(OH)3@MMCH exhibited high adsorption capacity of 105.72±5.99 mg P/g, and reached equilibrium within 2 hr. La(OH)3@MMCH could perform effectively in a wide pH range from 3.0 to 9.0 and in the presence of coexisting ions (including SO42−, Cl−, NO3−, HCO3−, SiO44− and HA). The adsorption-desorption experiment indicated that La(OH)3@MMCH could be easily regenerated by using NaOH-NaCl as the desorption agent, and 73.3% adsorption capacity remained after five cycles. Moreover, La(OH)3@MMCH was employed to treat surface water with phosphate concentration of 1.90 mg/L and showed great removal efficiency of 95.21%. Actually, MMCH showed high surface charge density of 34.38-59.38 meq/kg in the pH range from 3.0 to 11.0 and great swelling ratio of 3014.57% within 24 h, indicating that MMCH could produce the enhanced Donnan membrane effect to pre-permeate phosphate. Furthermore, the bifunctional structure of La(OH)3@MMCH enabled it to capture phosphate through electrostatic attraction and ligand exchange. All the results prove that La(OH)3@MMCH is a promising adsorbent for eutrophication control and phosphate recovery.

Cibacron blue F3GA incorporated immobilized metal chelate affinity sorbent as a high efficient affinity immobilization materials for catalase enzyme

Catalase is a metalloenzyme commonly found in almost all plant and animal tissues and catalyzes the conversion of hydrogen peroxide to less reactive molecules. It is used for the elimination of hydrogen peroxide in biological, biomedical, food and textile applications. For this purpose, a novel affinity sorbent [poly(methacrylic acid- N-isopropyl acrylamide-CB-Fe3+, (p(MAA-NIPAAM)-CB-Fe3+)] for the determination and it was first developed using MAA and NIPAAM monomers. After characterization with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray Photoelectron Spectroscopy (XPS), adsorption parameters were determined. Reusability of p(MAA-NIPAAM)-CB-Fe3+ sorbent was determined after by determining the appropriate desorption agent for desorption of adsorbed catalase in the developed sorbent. It was determined that catalase adsorption could be performed with 0.01 g of sorbent in 45 min. The maximum adsorption capacity for catalase adsorption was determined as 243.17 mg/g with the use of sorbent. The operational and storage stability of the immobilized catalase was found to be high as expected. The conversion of H2O2 can be successfully performed by the immobilized enzyme in the prepared sorbent. It has been proven that the affinity of catalase for its substrate is increased by immobilization.

Enhanced removal of bisphenol A using pine-fruit shell-derived hydrochars: Adsorption mechanisms and reusability

We synthesized NaOH-activated hydrochars via hydrothermal carbonization (HTC) of Brazilian pine fruit shells at HTC residence times of 24, 48, and 72 h. The hydrochars were used as adsorbents to remove bisphenol A (BPA) from aqueous solutions. The surface area of the samples can reach up to 2220 m2 g−1, and the maximum adsorption of BPA onto the surfaces was achieved at a pH of 7.0 (708 mg g−1). Adsorption occurred mainly via monolayer formation with a low retention time of the adsorbate (τ) on the surfaces, indicating that the BPA molecules reached the already occupied active sites and returned after undergoing heat exchange (τ > 0). Adsorption is an endothermic spontaneous process that results in a balance between entropic and enthalpic contributions. In such a reaction, ΔG°< 0, even with ΔH°> 0, the process occurs with an important increase in the entropy. The desorption was more efficient with ethanol and methanol than with HCl, NaOH, and NaCl owing to the dipole-dipole forces between the adsorbate and the alcohols. Additionally, the low desorption efficiency using acid, base, and salts can be attributed to competitive effects between the desorption agents and the active sites of the adsorbents.

Behaviors of Desorption Agents During Removal of Cs From Clay Minerals and Actual Soil

The behaviors of various desorption agents were investigated during the desorption of cesium (Cs) from samples of clay minerals and actual soil. Results showed that polymeric cation exchange agents (polyethyleneimine (PEI)) efficiently desorbed Cs from expandable montmorillonite, whereas acidic desorption solutions containing HCl or PEI removed considerable Cs from hydrobiotite. However, most desorption agents could desorb only 54% of Cs from illite because of Cs’s specific adsorption to selective adsorption sites. Cs desorption from an actual soil sample containing Cs-selective clay mineral illite ( PEI > NH4+, and the highest Cs desorption amount achieved using HCl was 83%. Unlike other desorption agents with only cation exchange capabilities, HCl can attack minerals and induce dissolution of metallic elements. HCl’s ability to both alter minerals and induce H+/Cs+ ion exchange is expected to promote Cs desorption from actual soil samples.

Adsorption and desorption of zinc and copper in acid mine drainage onto synthesized zeolite from coal fly ash

Synthetic zeolite is considered a more effective adsorbent due to its high purity and high removal efficiency. On the other hand, acid mine drainage contains various metal ions, such as zinc, copper, iron, and manganese which are toxic for the ecosystem in a certain concentration. One of the solutions to remove these metal ions is through adsorption. Therefore, the study of adsorption and desorption of zinc and copper onto synthetic zeolite was conducted. The synthetic zeolite was synthesized from coal fly ash and the acid mine drainage was prepared artificially. The adsorption experiment was carried out using a batch system. NaCl, H2SO4, and HNO3 were used as desorption agent. The adsorption studies revealed that the removal efficiency of both Zn2+ and Cu2+ onto the studied adsorbent decrease with the increase of adsorbate concentration. While the adsorption selectivity for multi-system synthetic AMD solution by the studied adsorbent were found to the order of Fe2+> Cu2+> Zn2+> Mn2+.After being reused three times, the synthetic zeolite shows a decrease in for Zn2+ and Cu2+ adsorption efficiency of about 10%. Furthermore, the desorption study shows the ineffective use of NaCl, H2SO4, and HNO3 as desorption agents in this study.

Process optimization and adsorption modeling using hierarchical ZIF-8 modified with Lanthanum and Copper for sulfate uptake from aqueous solution: Kinetic, Isotherm and Thermodynamic studies

In the current study, the hieratical zeolitic imidazole framework 8 (H/ZIF-8) and bimetallic H/ZIF-8, H/ZIF-8@La and H/ZIF-8@Cu, were prepared with a simple and green method using water as a solvent. Process parameters (temperature and time of crystallization), as well as compositional parameters (amount of 2-Methylimidazole and 2-(methylamino)ethanol), were studied. H/ZIF-8 samples were characterized with XRD, EDS, FE-SEM, TGA/DTA, FTIR, N2 isotherms, and their performance was evaluated for sulfate uptake from aqueous media. An experimental design was utilized in this study to optimize the independent variables using central composite design (CCD) under the response surface methodology (RSM) method. A significant agreement between the models and experimental data was verified by analysis of variance (ANOVA). The adsorption equilibrium models of Langmuir, Jovanovic, Freundlich, and Temkin isotherms were evaluated and the results described that the Langmuir model was the best with the experimental data. Different kinetic models were estimated and found that pseudo-second-order kinetic data were well-fitted for removal reaction. The determination of different thermodynamic parameters reflected that the sulfate uptake was spontaneous and feasible and that three H/ZIF-8 samples had an endothermic nature. The adsorption on H/ZIF-8 samples was not significantly influenced by the competing anions of nitrate, chloride and fluoride but phosphate displayed slightly greater negative effects. The used H/ZIF-8 samples could be regenerated and reused in eight consecutive cycles with a proper desorption agent. The results of sulfate removal from a real sample revealed that using H/ZIF-8 and two bimetallic H/ZIF-8 samples for sulfate removal from polluted waters is a promising alternative for sulfate recovery.