Multi-metal Solutions Research Articles

Biosorption of nickel, cobalt, zinc and copper ions by Serratia marcescens strain 16 in mono and multimetallic systems

The metallurgical industry is one of the main sources of heavy metal pollution, which represents a severe threat to life. Metals can be removed from aqueous solutions by using microbial biomasses. This paper analyses the heavy metal biosorption capacity of Serratia marcescens strain 16 in single and multimetallic systems. The results obtained show that Co(II), Ni(II) and Zn(II) biosorption in monometallic systems is two to three times higher than in the presence of bi-metallic and multimetallic solutions. Fourier transform infrared spectroscopy confirmed that carbonyl, carboxyl and hydroxyl were the main functional groups, as well as the amide bands I and II involved in metal uptake, which are present in external structures of the bacterial cell. The results obtained demonstrated the viability of S. marcescens strain 16 as a biosorbent for the design of eco-friendly technologies for the treatment of waste liquor.

Steel Slag and Autoclaved Aerated Concrete Grains as Low-Cost Adsorbents to Remove Cd2+ and Pb2+ in Wastewater: Effects of Mixing Proportions of Grains and Liquid-to-Solid Ratio

This study investigated the applicability of industrial by-products such as steel slag (SS) and autoclaved aerated concrete (AAC) grains (<0.105, 0.105–2, 2–4.75 mm) as low-cost adsorbents for simultaneous removal of Cd2+ and Pb2+ in wastewater. A series of batch adsorption experiments was carried out in single and binary-metal solutions of Cd2+ and Pb2+ by changing the mixing proportions of SS and AAC grains. In addition, the effect of the liquid-to-solid ratio (L/S) on the removal of Cd2+ and Pb2+ in multi-metal solution was examined. Results showed that SS grains had a high affinity with Cd2+ in the single solution, while AAC grains had an affinity with Pb2+. In the binary solution, the mixtures of SS and AAC grains removed both Cd2+ and Pb2+ well; especially, the tested adsorbents of SS+AAC [1:1] and SS+AAC [1:4] mixtures achieved approximately 100% removal of both metals. Based on the results in the multi-metal solutions, the metal removal % and selectivity sequence varied depending on the mixed proportions of SS and AAC grains and L/S values. It was found that the SS+AAC [1:1] mixture of SS and AAC grains showed 100% removals of Cd2+, Pb2+, Cu2+, Ni2+, and Zn2+ simultaneously at L/S = 10 and 60.

Activated carbons from passion fruit shells in adsorption of multimetal wastewater.

This work aims to use a solid agro-industrial residue (passion fruit shells-PF) to manufacture different activated carbons (ACs) capable to retain Cr3+, Cu2+, and Ni2+ on synthetic wastewater. The PF was carbonized and chemically activated with three precursors, giving rise to three ACs: phosphoric acid ([Formula: see text]), sodium acetate ([Formula: see text]), and potassium hydroxide (ACKOH). The ACs were characterized by SEM, ASAP, FTIR, and pH-PZC. The adsorption phenomena were studied by kinetic and isotherm models. The efficiency of the process was investigated in mono- and multimetallic solution with two-way ANOVA and Tukey test at 95% confidence interval. The physical-chemical modifications in the solid increased the surface area, the porosity, and the heterogeneity. The phenomena had a better fit to the pseudo-second-order kinetic model and to the Freundlich isotherm model. Analyzing the interaction between the ACs and the composition of the solutions, the selectivity of the solid and the competition for activated sites were verified. Efficiencies higher than 95% were obtained for Ni2+, 80% for Cu2+, and 70% for Cr3+. The viability of the process in mono- and multimetallic solutions opens the possibility of integrated management of metallic wastewater and agro-industrial residues.

Extraction of gold(III) using novel gemini-type benzimidazole ionic liquid from hydrochloric acid medium

In this study, a novel gemini-type benzimidazole ionic liquid [C6BIM2][NTf2]2 was synthesized for efficient extract gold(III) from hydrochloric acid medium. Firstly, a series of parameters (e.g., vibrating time, the extractant concentration, acidity and salinity) were optimized and obtained the optimal extraction condition. Under this condition, the extraction efficiency can reach 98.42%, along with the distribution ratio of 186.87. Through the response surface methodology (RSM) model optimization, the amount of [C6BIM2][NTf2]2 corresponding to different HCl concentration was determined for gold(III) extraction during actual operation. Then, verified the anion exchange mechanism with the aid of Job’s method, UV–vis, FT-IR and 13C NMR. Thermodynamic parameters were calculated and implied that the extraction reaction was an exothermic and spontaneous process. Furthermore, organic phase loaded with gold(III) was easy to be completely stripped by CS(NH2)2/ HCl solution and its extraction ability was kept constant after 5 cycles extraction experiments. Meanwhile, [C6BIM2][NTf2]2 has a superb ability to select gold(III) in the multi-metal solution. In general, [C6BIM2][NTf2]2 showed distinguished selectivity and extraction ability for gold(III) from secondary resources, which was claimed to be a promising new style extractant.

Selective Cobalt Precipitation for the Synthesis of Precursors for Cathode Materials of Li-Ion Batteries

Due to the increase in energy storage for consumer electronics, stationary application and above all for electrical vehicles, the manufacturing of Li-ion batteries has dramatically increased in the past few years. Unfortunately, cathode materials still often use cobalt, and consequently, an increase of 10% per year of the world’s cobalt consumption has been observed. Li-ion batteries represent 60% of the use of extracted cobalt today (more than 80% expected in 2030), which is classified as a critical material since 2011 by the European Commission. Battery grade cobalt is produced by only few countries. 60% is provided by the Democratic Republic of Congo. In order to avoid reliance on cobalt supplying, European industry should have to develop alternative solution.We present here a new way to extract cobalt from a solution of battery-waste materials. Through a one-step process, it is possible to recover the cobalt, selectively, in a solution composed in majority of cobalt, nickel and manganese.The goal of the process is to form a cobalt-based Metal Organic Framework compounds (MOF) from a multi-metals based solution. The contact of a well-designed ligand with model multi-metallic solution of nickel, manganese and cobalt, under specific conditions, creates a precipitate, which is recovered by centrifugation or filtration. The XRD analysis of the resulting material demonstrates a crystalline structure, and its ICP analysis shows up to 99% of cobalt composition of the metallic nodes of the material. The same process with a real battery waste solution enables the formation of a precipitate made of 94% of cobalt (among the metallic centers).The resulting MOF can be used as a precursor for synthetizing cathode materials. In order to complete the described closed-loop concept, it is indeed possible to assemble a coin-cell from those products. The well define crystalline structure of the MOF makes them suitable for other industrial application, such as separation or catalysis (open-loop concept).We are focusing on better understanding of this selectivity process. Density Functional Theory (DFT) calculations are performed, as a tool to evaluate the energy of the different complexes in solution at all states of the nucleation and growth of the MOF. Moreover, the ligand used can form a MOF with each of the metals present in solution. Some nickel and manganese phases (more or less soluble) are involved during the process as a function of the reaction conditions. Identifying their nature and formation is another axis for the understanding of the presented work. Modelling these phenomena could help to determine the reaction that occurs, how the selectivity happens, and why the growing material is made of cobalt only (no other metal).

Native Desmodesmus sp. and Chlorella sp. isolated from the Reconquista River display a different binding preference for Cu(II) and Zn(II)

The present work was developed to study the metal removal performance of unicellular algae isolated from the Reconquista River and to evaluate the effect of the presence of more than one metal in the removal process. Thus, native species of unicellular algae were isolated from the highly contaminated Reconquista River. All of the isolates were classified, at genus level, based on their morphological appearance. Nine isolates were screened for their Zn(II) removal capacities. Chlorella sp. RR5 and Desmodesmus sp. RR7 were selected based on their removal performance, and their potential in the remediation of multiple metals was analyzed. Therefore, zinc (Zn(II)), copper (Cu(II)), and chromium (Cr(VI)) removal was evaluated in mono- and multi-metallic solutions. Biosorption capacities were high (0.8–1.8 mmol g−1) for Zn(II) and Cu(II) in mono-metallic solutions. Removal capacities decreased up to 48% in multi-metallic solutions. Interestingly, when multi-metallic systems were considered, each strain showed a metal preference. Chlorella sp. removed better Cu(II) meanwhile Desmodesmus sp. showed a preference for Zn(II). Thus, a metal-binding selectivity in each strain was determined. Chromium (VI) remediation was almost null in the conditions analyzed in this work. Fourier transformation infrared spectroscopy (FT-IR) analysis showed that polysaccharides were the main functional group involved in metal adsorption and, in some cases, also the carboxylates played an important role.Overall, we were able to analyze a new source of algal diversity and perform a metal removal characterization of them, leading to the identification of a metal selectivity based on the characteristics of the tested algal strains.

Effect of hydrogel based soil amendments on heavy metal uptake by spinach grown with wastewater irrigation

Food crops irrigated with wastewater can uptake heavy metals, causing serious health ailments in humans. Use of a polyacrylamide superabsorbent polymer hydrogel and the same hydrogel mixed with pyrolyzed plantain peel biochar as soil amendments are proposed to reduce heavy metal uptake by wastewater-irrigated spinach (Spinacia oleracea L.) plants. A sorption test was carried out to establish the ability of these treatments to bind the heavy metals. In a lysimeter field experiment, the amendments were mixed in the top 0.10 m of soil (1% w/w) and spinach plants were grown using synthetic wastewater irrigation. After each irrigation, soil samples were obtained at different depths (0, 0.10, 0.30, and 0.60 m from the surface) for heavy metal analysis. Spinach leaves, root, and stem samples were obtained at the harvest for metal analysis. Sorption test results showed that the hydrogel-biochar amended soil adsorbed 0.80, 0.46, and 0.44 mg g−1 of cadmium, copper, and zinc, respectively, from a 0.5 mM multi-metal solution; the hydrogel treatment adsorbed 0.59, 0.41, and 0.24 mg g−1 of the metals, respectively. These amounts were at least 90% more than those adsorbed by the non-amended soil. In terms of the total metal uptake by spinach leaves, the hydrogel-biochar mix treatment performed better than the hydrogel treatment; it reduced the total uptake by 48%, whereas the hydrogel treatment was only able to reduce it by 15% when compared to the control that exhibited a total metal load of 1028 mg kg−1. Both treatments were able to significantly (p < 0.05) reduce copper uptake in plant stems, and exhibited the potential to reduce chromium, copper, and iron uptake by spinach leaves.

Production of a nickel-based catalyst for urea electrooxidation using spent batteries as raw material: Electrochemical synthesis and implications from a circular economy stand-point

In this work, we leached the electrochemically active powder (black mass) from spent Ni-MH batteries in an aqueous solution containing citric acid and hydrogen peroxide. The obtained multimetallic solution was chemically analyzed and its speciation simulated via thermodynamic software. Electrolysis of the leachate rendered a new metal coating containing Ni, Zn and Co on a copper substrate. The electrochemical stability of the alloy-coated electrode was evaluated in a 1 M KOH solution through cyclic voltammetry analysis and compared against a pure‑nickel electrode standard. Moreover, the catalytic capacity of the alloyed electrode was studied by cyclic voltammetry and chronoamperometric analysis using a mixture of 1 M KOH and 0.3 M urea. During the electrooxidation of urea, the Ni-Zn-Co coated electrode exhibited better performance than the pure‑nickel catalytic electrode used as standard, with a current response 1.8 times higher than pure nickel and 9.4% lower energy consumption than pure nickel. This promising result opens the possibility for targeting the manufacturing of catalytic electrodes as a viable end-user of the recovered metal values contained in spent batteries. As a result, a conceptual process flow diagram was devised for this novel valorization procedure. The application of these alloyed electrodes for the remediation of urea-containing water was conceptually proposed, as well. From a circular economy standpoint, this work describes an industrial ecosystem involving the life cycle of Ni-MH batteries, the electroplating industrial process, and the environmental services. Consequently, an innovative and symbiotic materials flow was depicted for wastewater treatment based on electrooxidation procedures.

Synthesis of Eco-Friendly Biopolymer, Alginate-Chitosan Composite to Adsorb the Heavy Metals, Cd(II) and Pb(II) from Contaminated Effluents.

Efficient removal of Cd(II) and Pb(II) from contaminated water is considered a fundamental point of view. Synthetic hydrogel biopolymers based on chitosan and alginate (cost-effective and eco-friendly) were successfully designed and characterized by highly efficient removal contaminants. The sorbents are characterized by FTIR, SEM-EDX, TGA, XPS analyses and textural properties which are qualified by N2 adsorption. The sorption properties are firstly investigated by the effect of pH, sorption isotherms, uptake kinetics, and selectivity from multi-metal solution with equi-molar concentration. The sorbent with 1:3 ratios (of chitosan and alginate respectively) is the most effective for metal removal (i.e., 0.81 mmol Cd g−1 and 0.41 mmol Pb g−1). Langmuir and Sip’s models fitted better the adsorption isotherms compared to the Freundlich model. Uptake kinetics was well fitted by pseudo-first-order rate equation, while the saturation was achieved within 40 min. The sorbent shows good reproducibility through duplicate the experiments with negligible decreasing efficiency (>2.5%). The sorbent was applied for water treatment on samples collected from the industrial area (i.e., 653 and 203 times over the MCL for Cd(II) and Pb(II) respectively according to WHO). The concentration of Cd and Pb was drastically decreased in the effluents as pH increased with removal efficiency up to 99% for both elements at pH 5.8 and SD equivalent 1 g L−1 for 5 h.

A systematic study on extraction and separation of scandium using phosphinic acid by both solvent extraction and hollow fibre membrane

ABSTRACT A method for separation of scandium and preparation of scandium oxide using hollow fibre supported liquid membrane (HFSLM) was described. Scandium was separated from a multi metal solution bearing copper, nickel, cobalt, zinc, iron, manganese and scandium using bis (2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272) as the mobile carrier. The effect of parameters such as pH, extractant concentration, flow rate, metal ion concentration and strip solution concentration on extraction of scandium was investigated and maximum flux was obtained at pH 2.0, Cyanex 272 concentration of 0.3 M, flow rate of 240 mL/min and 1.0 M H2SO4 in strip solution. From the equilibrium studies the extracted species was determined to be ScR3.3RH. A comparative study between solvent extraction and HFSLM has also been carried out to predict the efficiencies of both the techniques for the present system which could be useful for the treatment of industrial wastes bearing very low amount of Sc. It was observed that Sc recovery using Cyanex 272 with HFSLM and solvent extraction was 99.9 and 91%, respectively. Scandium was separated from other metal ions with high separation factors which followed the trend Sc/Ni < Sc/Mn < Sc/Co < Sc/Zn < Sc/Fe < Sc/Cu. High pure scandium oxide (Scandia) was prepared from the strip solution by precipitation with oxalic acid and thermal decomposition at 750°C for 1 h.

Efficient and Selective Adsorption of Neodymium on Expanded Vermiculite

In this study, expanded vermiculite (EV) was applied to the adsorption of neodymium (Nd) from an aqueous solution with focus on the description of the kinetics and the mechanism of adsorption, determination of the best eluent, and selectivity. The EV was characterized before and after the adsorption process by the morphology, composition, textural properties (specific surface area, density, and porosity), and functional groups. The adsorption experiments showed that under optimal conditions, using 0.7 g of adsorbent and at pH 3.3, the efficiency achieved an enhanced adsorption percentage of 98.7%, which represents an adsorption capacity of 0.205 mmol/g. The external mass and diffusional resistance controlled the mass transfer, and ion exchange occurred mainly with magnesium cations. The proposed mechanism of adsorption was cation exchange in the interlayer region of the vermiculite and the formation of outer-sphere complexes. Calcium chloride was the most suitable eluent, regarding efficiency and low toxicity. The adsorbent preferably adsorbed Nd from a multimetal solution, achieving enhanced values of selectivity. Regarding characterization, the EV presented a well-organized structure, a lamellar morphology, and typical functional groups such as Al–O and Si–O. Thus, the EV adsorbed Nd quickly and efficiently, and the ion-exchange mechanism of adsorption allows the selective adsorption of Nd and safe desorption by the exchange with Ca2+.

METODOLOGIA DE SUPERFÍCIE DE RESPOSTA PARA OTIMIZAÇÃO DA ADSORÇÃO DE METAIS PESADOS EM UMA SOLUÇÃO MULTI-METAIS POR PELLETS DE ZEÓLITAS DE BENTONITA-CAOLIM

Background: Heavy metals contamination of surface and groundwater is a major environmental problem. Clay minerals are porous and are efficient to adsorb metal ions. Amongst the available treatment technologies, adsorption is the most cost-effective, easy to operate, scalable, and replicable to remediate heavy metals from water solution. Aim: This study aimed to assess the adsorption performance of clay pellets of natural aluminosilicates, bentonite (29%), kaolin (4%) and zeolite (67%) to remove heavy metals from aqueous solutions. Methods: The effect of optimal operating conditions like contact time, adsorbent dose, pH, and heavy metals initial concentration has been studied. Kinetic and equilibrium studies were also performed. Adsorbents were characterized using FTIR analysis. Results and Discussion: Optimum values for contact time, adsorbent dose, pH, and initial concentration of lead, copper, and cadmium were; 240 min; 25 g/L; 4.3; and 4mg/L, 7 mg/L and 2 mg/L, respectively. The Langmuir isotherm was the best-fitted isotherm model for the three metals. Adsorption kinetics showed that the lead and copper adsorption followed the pseudo-second-order model while cadmium suited with the pseudo-first-order model. The selectivity of the pellets towards the metal ions was in the order of Pb &gt; Cu &gt; Cd. Conclusions: The new combination of bentonite-kaolinite-zeolite pellets worked well in tertiary wastewater treatment and successfully utilized as a natural adsorbent in multimetal solution. The results confirmed that the used clay pellets have better adsorption capacity than many other reported studies. Maximum adsorption capacity can be further increased by adjusting the calcination temperature and applying chemical treatments to the clay pellets before extrusion. The response surface analysis evaluated the predicted optimal values for the four operating factors.

RESPONSE SURFACE METHODOLOGY FOR OPTIMIZATION OF HEAVY METAL ADSORPTION IN A MULTIMETAL SOLUTION BY BENTONITE-KAOLIN-ZEOLITE PELLETS

Background: Heavy metals contamination of surface and groundwater is a major environmental problem. Clay minerals are porous and are efficient to adsorb metal ions. Amongst the available treatment technologies, adsorption is the most cost-effective, easy to operate, scalable, and replicable to remediate heavy metals from water solution. Aim: This study aimed to assess the adsorption performance of clay pellets of natural aluminosilicates, bentonite (29%), kaolin (4%) and zeolite (67%) to remove heavy metals from aqueous solutions. Methods: The effect of optimal operating conditions like contact time, adsorbent dose, pH, and heavy metals initial concentration has been studied. Kinetic and equilibrium studies were also performed. Adsorbents were characterized using FTIR analysis. Results and Discussion: Optimum values for contact time, adsorbent dose, pH, and initial concentration of lead, copper, and cadmium were; 240 min; 25 g/L; 4.3; and 4mg/L, 7 mg/L and 2 mg/L, respectively. The Langmuir isotherm was the best-fitted isotherm model for the three metals. Adsorption kinetics showed that the lead and copper adsorption followed the pseudo-second-order model while cadmium suited with the pseudo-first-order model. The selectivity of the pellets towards the metal ions was in the order of Pb &gt; Cu &gt; Cd. Conclusions: The new combination of bentonite-kaolinite-zeolite pellets worked well in tertiary wastewater treatment and successfully utilized as a natural adsorbent in multimetal solution. The results confirmed that the used clay pellets have better adsorption capacity than many other reported studies. Maximum adsorption capacity can be further increased by adjusting the calcination temperature and applying chemical treatments to the clay pellets before extrusion. The response surface analysis evaluated the predicted optimal values for the four operating factors.

The effect of pyrolysis temperature and feedstock on date palm waste derived biochar to remove single and multi-metals in aqueous solutions

In this study, leaf and frond date palm waste as feedstock was used to derive biochars. The effects of pyrolysis temperatures on their physical and chemical properties, and their capacity to remove copper, iron, nickel and zinc from single and multi-metal solutions at various pH values were investigated. Analytical and spectroscopic techniques such as scanning electron microscopy, energy dispersive X-ray, Fourier transform infrared spectroscopy, X-ray diffraction, carbon, hydrogen, nitrogen, sulfur elemental analysis, Brunauer Emmett Teller analysis were conducted for characterization. The pore volume, surface area, pH, and total carbon content of date palm leaf and frond biochar increased while functional groups and hydrogen, nitrogen and oxygen content of biochar decreased with increasing pyrolysis temperature compared to feedstock. The removal efficiencies and sorption capacity for single and mixed metal ions were found between 98 and close to 100% and 2.4 and 3.0 mg g− 1 by leaf and frond biochar samples at pH > 6, respectively. Biochar obtained from different feedstock at different pyrolysis temperature did not show any statistically significant improvements on the removal of single or mixed metals from aqueous solutions. The date palm leaf or frond biochar obtained at low pyrolysis temperature is as effective to remove metals as the ones obtained at high pyrolysis temperatures. Therefore, to consume less energy to produce biochar at lower temperature which exhibits same effective removal efficiency will be a win-win solution in terms of sustainability and economy. As a result, date palm waste biochar can be effectively used to remove metals in water and wastewater.

Selective removal of lead ions from aqueous solutions using SiO2–MoO3: Isotherm, kinetics and thermodynamic studies

This study reveals novel data on adsorptive removal of Pb(II) from single metal solution, as well as from multi-metal solution containing Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Mn(II), Ni(II) and Zn(II) ions along with Pb(II) using inorganic SiO2–MoO3 sorbent in a batch system. The results of multi-metal solution system were strongly pH-depended and due to occurred precipitation of Fe(III) in the form of hydroxide. The parameters affecting the sorption efficiency (contact time, sorbent dosage and initial analyte concentration) were evaluated for single solution system. The optimal conditions for SiO2–MoO3 sorbent indicated high affinity toward Pb(II) ions within following process parameters; pH value 3, sorbent dosage 50 ​mg and contact time 60 ​min for maximum Pb2+ concentration of 100 ​mg/L. The adsorption data for Pb(II) utilizing SiO2–MoO3 best fit to pseudo-second-order kinetic model (R2 ​= ​0.9998) and Langmuir isotherm model (R2 ​= ​0.9320) with an adsorption capacity of 222.20 ​mg/g and Reff >95%. According to thermodynamic study, the adsorption process is feasible, spontaneous and exothermic (ΔG ​= ​−18.6 ​kJ/mol, ΔH ​= ​−7.5 ​kJ/mol and ΔS ​= ​37.32 ​J/mol K). The results of present study demonstrated that SiO2–MoO3 material as a renewable sorbent for Pb(II) removal.

Facile cross-link method to synthesize chitosan-based adsorbent with superior selectivity toward gold ions: Batch and column studies

The recovery of gold from wastewater has received significant attention in the last years due to its high economic value and low availability. A novel chitosan-based adsorbent (CS-GTU) was successfully synthesized by using formaldehyde as a crosslinker between chitosan and guanylthiourea, and applied for selective adsorption of AuIII from an aqueous medium. Through batch experiments, the maximum adsorption capacity of CS-GTU for AuIII could reach up to 695.63 mg/g at pH 5.0, and the adsorption process followed the Pseudo-second-order kinetic and Langmuir isotherm models, indicating that the monolayer chemisorption possibly occurred on the adsorbent surfaces. The adsorption was an enthalpy driven and spontaneous chemical process based on thermodynamic analysis. Furthermore, the adsorbent has demonstrated outstanding selectivity toward AuIII from multi-metallic solutions, and five cycled experiments of adsorption-desorption showed that CS-GTU could be efficiently regenerated. Experimental breakthrough curves were successfully simulated by using the Thomas model, which can fit the experimental data with the correlated curve (R2 > 0.9) well. This improvement in adsorption was a consequence of the complexation and electrostatic attraction of gold ions with the abundant sulfur/nitrogen-containing groups. The CS-GTU beads can be considered as a suitable and efficient adsorbent for gold ions in aqueous solutions.

Biosorption of Ag+ and Nd3+ from single- and multi-metal solutions (Ag+, Nd3+, and Au3+) by using living and dried microalgae

Biosorption of Ag+ and Nd3+ from single- and multi-metal solutions (Ag+, Nd3+, and Au3+) by using living and dried microalgae

Selective adsorption of palladium(II) from aqueous solution using epichlorohydrin crosslinked polyethylenimine-chitin adsorbent: Batch and column studies

Selective adsorption of platinum group metals (PGMs) from mixed metals solution is still a challenging issue. Here, we reported the effective palladium (Pd(II)) separation from a multi-metal solution by epichlorohydrin crosslinked polyethylenimine-chitin composite (PEI-chitin), a pH-dependent selective adsorbent. The possible adsorption mechanism of PEI-chitin for Pd(II) was revealed by FE-SEM-EDS, FTIR, and XPS characterization. The adsorption performance of PEI-chitin towards Pd(II) was evaluated by batch and column experiments. In batch adsorption experiments, the theoretical Pd(II) uptake on PEI-chitin calculated using the Langmuir model was 872.1 mg/g, which was 4.4 and 8.5 times higher than that of the Amberjet 4200 and SYL-0830, respectively. The Pseudo-first-order model described the adsorption of PEI-chitin for Pd(II), and the adsorption equilibrium was reached within 10 min, which was faster than that of Amberjet 4200 and SYL-0830. The effect of pH experiment proved that the optimal pH for selective adsorption was 1.0. The column adsorption properties were measured at different flow rates, bed heights, and initial concentrations, and the breakthrough curves were well represented by the Thomas and Yoon-Nelson models. Moreover, the PEI-chitin demonstrated good selective performance for Pd(II) in the column system. The exhausted adsorbent was easily regenerated under acidified thiourea solutions and was reusable repeatedly.

A Comparative Adsorption Study on Low-cost Synthetic, Nano and Doped ZnO for the Removal of Copper Surfactants Urea Complexes: Equilibrium, Kinetics, and Thermodynamics

&lt;P&gt;Background: The effective removal of heavy metals from aqueous wastes is among the most important issues for many industrialized countries. Present paper reports about the synthesis of copper neem urea complex (CNU) and its characterization using elemental and spectroscopic techniques such as IR, NMR, and ESR. &lt;/P&gt;&lt;P&gt; Methods: The NPs of ZnO and doped with SiO&lt;sub&gt;2&lt;/sub&gt; which was extracted from industrial ash’s) was synthesized by precipitation method and characterized through UV, SEM-EDX and XRD techniques. Three low cost adsorbents such as synthetic ZnO, nano ZnO and doped ZnO with SiO&lt;sub&gt;2&lt;/sub&gt; were chosen for the adsorption of copper surfactant complex of urea from non-aqueous solutions i.e. petroleum ether. Effect of various parameters like contact time, pH, adsorbent dosage, temperature and initial metal concentration on the removal through degradation and adsorption of CNU were investigated and optimized. &lt;/P&gt;&lt;P&gt; Results: Isothermal studies indicated that the adsorption of CNU followed Langmuir adsorption isotherm. Kinetic studies indicated that removal of the CNU by the three adsorbents followed second order kinetics. With a maximum adsorption capacity of 7.58 mg/g using all three adsorbents showed an effective and efficient removal 95.8% of CNU from non-aqueous solutions by using ZnO doped with SiO&lt;sub&gt;2&lt;/sub&gt; compare to synthetic ZnO and nano ZnO. This is the first report of removal of the CNU complex based on the three adsorbents. &lt;/P&gt;&lt;P&gt; Conclusion: The potential of application for the treatment of solutions containing these complexes in multi-metal solutions is indicated.&lt;/P&gt;

Highly selective extraction of Pd(II) using functionalized molecule of 2-[(2-ethylhexyl)thio]benzoxazole and its Pd(II) extraction mechanism

• A functionalized extractant EHBXS with three heteroatoms (S, N and O atoms) which can selectively coordinated with Pd(II) was synthesized by one-step reaction. • EHBXS has high selectivity for Pd(II) and can effectively remove Pd(II) from multi-metal solution at desired extraction conditions. • The coordination mechanism between Pd(II) and EHBXS was proved by slope method, FT-IR, 1 H NMR, 13 C NMR spectroscopies, and the X-ray crystal structure of Pd(EHBXS) 2 Cl 2 . In view of the separation and recycling of Pd(II) from multi-metal aqueous solution, a functionalized extractant of 2-[(2-ethylhexyl)thio]benzoxazole (EHBXS) with excellent selectivity for Pd(II) was synthesized and used to extract Pd(II) for the first time. The effects of EHBXS concentration, HCl concentration, organic/aqueous (O/A) phase ratio, contact time, and regeneration of EHBXS were investigated in detail. The extraction efficiency of Pd(II) was almost 100 % while the co-extraction efficiencies of Pt(IV), Rh(III), Cu(II), Fe(III) and Ni(II) existed in the aqueous solution were less than 10 %, which indicates that EHBXS is an effective extractant and can effectively remove Pd(II) from other metals at desired extraction conditions. Thiourea ((NH 2 ) 2 CS) solution (1.0 mol/L) could be used as an effective Pd(II) stripping agent and the one-step stripping efficiency of Pd(II) was higher than 98 %. EHBXS has excellent regeneration ability and the extraction efficiency of Pd(II) with regenerated EHBXS reaches to 87% even after 7 cycles. Moreover, the coordination mechanism between EHBXS and Pd(II) has been proven via the slope method, FT-IR spectra, 1 H NMR, 13 C NMR and single X-ray diffraction. Pd(II) and EHBXS formed a 1:2 complex of Pd(EHBXS) 2 Cl 2 during extraction. Pd(II) was coordinated with two Cl atoms and two EHBXS, and thus formed Pd(EHBXS) 2 Cl 2 molecule, in which EHBXS was coordinated with Pd(II) via the N atom in the benzoxazole ring as neutral unidentate ligand.