Nanofibrous membrane of polyacrylonitrile with efficient adsorption capacity for cadmium ions from aqueous solution: Isotherm and kinetic studies

The nanofibrous membrane of polyacrylonitrile (NMP) was successfully synthesized after NaOH and NaHCO₃ treatment aiming its functionalization using electrospinning for cadmium ion (Cd²⁺) adsorption. Field emission scanning electron microscopy (FE-SEM) revealed that small particles attached to the surface of functionalized PAN nanofibers. Equilibrium was attained after 60 min following a rapid uptake of Cd²⁺ with maximum adsorption capacity and percentage removal at an optimum solution pH of 7.0. The adsorbent dose of 0.3 g and 90 mg L⁻¹ of initial Cd²⁺ concentration yielded the maximum adsorption capacity. The pseudo-second-order kinetic model was the best fitted to the adsorption data, indicating that the chemisorption is the controlling mechanism of adsorption. The physisorption was proposed based on the calculated values of the mean free energy of adsorption from the D–R isotherm (E < 8 kJ mol⁻¹). Furthermore, three-parameter isotherm models indicated the homogeneous and heterogeneous Cd²⁺ adsorption onto NMP adsorbent.     

An ion-imprinted amino-functionalized silica gel sorbent prepared by hydrothermal assisted surface imprinting technique for selective removal of cadmium (II) from aqueous solution

A new ion-imprinted amino-functionalized silica gel sorbent was synthesized by the hydrothermal-assisted surface imprinting technique using Cd²⁺ as the template, 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (AAAPTS) as the functional monomer, and epichlorohydrin as the cross-linking agent (IIP-AAAPTS/SiO₂) for the selective removal of Cd²⁺ from aqueous solution, and was characterized by FTIR, SEM, nitrogen adsorption and the static adsorption-desorption experiment method. The specific surface area of the IIP-AAAPTS/SiO₂ sorbents was found to be 149 m² g⁻¹. The results showed that the maximum static adsorption capacities of IIP-AAAPTS/SiO₂ sorbents by hydrothermal heating method and by the conventional heating method were 57.4 and 31.6 mg g⁻¹, respectively. The IIP-AAAPTS/SiO₂ sorbents offered a fast kinetics for the adsorption and desorption of Cd(II). The relative selectivity coefficients of IIP-AAAPTS/SiO₂ sorbents for Cd²⁺/Co²⁺, Cd²⁺/Ni²⁺, Cd²⁺/Zn²⁺, Cd²⁺/Pb²⁺ and Cd²⁺/Cu²⁺ were 30.68, 14.02, 3.00, 3.12 and 6.17, respectively. IIP-AAAPTS/SiO₂ sorbents had a substantial binding capacity in the range of pH 4-8 and could be used repeatedly. Equilibrium data fitted perfectly with Langmuir isotherm model compared to Freundlich isotherm model. Kinetic studies indicated that adsorption followed a pseudo-second-order model. Negative values of ΔG° indicated spontaneous adsorption and the degree of spontaneity of the reaction increased with increasing temperature. ΔH° of 26.13 kJ mol⁻¹ due to the adsorption of Cd²⁺ on the IIP-AAAPTS/SiO₂ sorbents indicated that the adsorption was endothermic in the experimental temperature range.     

Removal of heavy metals from aqueous solutions using Fe3O4, ZnO, and CuO nanoparticles

This study investigated the removal of Cd²⁺, Cu²⁺, Ni²⁺, and Pb²⁺ from aqueous solutions with novel nanoparticle sorbents (Fe₃O₄, ZnO, and CuO) using a range of experimental approaches, including, pH, competing ions, sorbent masses, contact time, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The images showed that Fe₃O₄, ZnO, and CuO particles had mean diameters of about 50?nm (spheroid), 25?nm (rod shape), and 75?nm (spheroid), respectively. Tests were performed under batch conditions to determine the adsorption rate and uptake at equilibrium from single and multiple component solutions. The maximum uptake values (sum of four metals) in multiple component solutions were 360.6, 114.5, and 73.0?mg?g^?1, for ZnO, CuO, and Fe₃O₄, respectively. Based on the average metal removal by the three nanoparticles, the following order was determined for single component solutions: Cd²⁺?>?Pb²⁺?>?Cu²⁺?>?Ni²⁺, while the following order was determined in multiple component solutions: Pb²⁺?>?Cu²⁺?>?Cd²⁺?>?Ni²⁺. Sorption equilibrium isotherms could be described using the Freundlich model in some cases, whereas other isotherms did not follow this model. Furthermore, a pseudo-second order kinetic model was found to correctly describe the experimental data for all nanoparticles. Scanning electron microscopy, energy dispersive X-ray before and after metal sorption, and soil solution saturation indices showed that the main mechanism of sorption for Cd²⁺ and Pb²⁺ was adsorption, whereas both Cu²⁺ and Ni²⁺ sorption were due to adsorption and precipitation. These nanoparticles have potential for use as efficient sorbents for the removal of heavy metals from aqueous solutions and ZnO nanoparticles were identified as the most promising sorbent due to their high metal uptake.     

Ion exchange and adsorption equilibrium studies on clinoptilolite, bentonite and vermiculite

In the present paper three natural minerals used in many industrial and environmental applications namely zeolite clinoptilolite and the clays bentonite and vermiculite are studied by utilising ion exchange and adsorption. In particular, the Dubinin-Astakhov adsorption isotherm is used modified by introducing a solubility-normalized adsorption potential for studying the ion exchange process. The equation, is applied in experimental isotherms in order to determine adsorption energy and heterogeneity parameter for the ion exchange of Pb²⁺ in the natural minerals. The results indicate that the modified Dubinin-Astakhov adsorption isotherm represents the experimental data well and at the same time provides the heterogeneity parameter of the materials, which is an important adsorbent physical parameter as well as the adsorption energy. In order to deepen the study and link the results to the pore structure BET analysis is presented as well.     

Application of modificated magnetic nanomaterial for optimization of ultrasound-enhanced removal of Pb2+ ions from aqueous solution under experimental design: Investigation of kinetic and isotherm

Magnetic γ-Fe₂O₃ nanoparticles modificated by bis(5-bromosalicylidene)-1,3-propandiamine (M-γ-Fe₂O₃-NPs-BBSPN) and characterized by field emission scanning electron microscopy (FE-SEM), Fourier transforms infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). This modified compound as novel adsorbent was applied for the ultrasound-assisted removal of Pb²⁺ ion in combination with flame atomic absorption spectroscopy (FAAS). The influences of the effective parameters including initial Pb²⁺ ion concentration, pH, adsorbent mass and ultrasound time were optimized by central composite design (CCD). Maximum removal percentage of Pb²⁺ ion which obtained at 25 mg L⁻¹ of Pb²⁺, 25 mg of adsorbent and 4 min mixing with sonication at pH 6.0. The precision of the equation obtained by CCD was confirmed by the analysis of variance and calculation of correlation coefficient relating the predicted and the experimental values of removal percentage of Pb²⁺ ion. The kinetic and isotherm of ultrasound-assisted removal of Pb²⁺ ion was well described by second-order kinetic and Langmuir isotherm model with maximum adsorption capacity of 163.57 mg g⁻¹.     

Application of bifunctional Saccharomyces cerevisiae to remove lead(II) and cadmium(II) in aqueous solution

A magnetic adsorbent, EDTAD-functionalized Saccharomyces cerevisiae, has been synthesized to behave as an adsorbent for heavy metal ions by adjusting the pH value of the aqueous solution to make carboxyl and amino groups protonic or non-protonic. The bifunctional Saccharomyces cerevisiae (EMS) were used to remove lead(II) and cadmium(II) in solution in a batch system. The results showed that the adsorption capacity of the EMS for the heavy metal ions increased with increasing solution pH, and the maximum adsorption capacity (88.16 mg/g for Pb²⁺, 40.72 mg/g for Cd²⁺) at 10 °C was found to occur at pH 5.5 and 6.0, respectively. The adsorption process followed the Langmuir isotherm model. The regeneration experiments revealed that the EMS could be successfully reused.     

Adsorption kinetics,isotherms, and thermodynamic studies for the adsorption of Pb<Superscript>2+</Superscript> and Hg<Superscript>2+</Superscript> metal ions from aqueous medium using Ti(IV) iodovanadate cation exchanger

In the current study, Ti(IV) iodovanadate cation exchanger (TIV) was synthesized and applied for the removal of Pb²⁺ and Hg²⁺ metal ions from the aqueous medium. The adsorption studies were performed by the batch techniques and adsorption parameters viz. contact time, pH, initial metal ion concentration, and temperature were also investigated. The optimum adsorption of Pb²⁺ (95 %) and Hg²⁺ (65 %) were observed at pH 6. The pseudo-second order equation represented the adsorption kinetics with high correlation coefficient. Langmuir model showed the best fitting to the isotherm equilibrium data, with a maximum adsorption capacity of 18.8 mg g^?1 for Pb²⁺ and 17.2 mg g^?1 for Hg²⁺. Furthermore, thermodynamic factors, i.e., ΔG, ΔH, and ΔS, indicated that adsorption of Pb²⁺ and Hg²⁺ onto TIV were spontaneous, endothermic, and feasible in the temperature range of 293–323 K.     

Studies on adsorptions of metallic ions in water by zirconium glyphosate (ZrGP): Behaviors and mechanisms

A new adsorbent named zirconium glyphosate [Zr(O₃PCH₂NHCH₂COOH)₂·0.5H₂O, denoted as ZrGP] and its selective adsorptions to Pb²⁺, Cd²⁺, Mg²⁺ and Ca²⁺ ions in water were reported in this paper. Compared to other zirconium adsorbents, such as zirconium phosphate [Zr(HPO₄)₂], ZrGP exhibited highly selective adsorption to Pb²⁺ in solution which contained Pb²⁺, Cd²⁺, Mg²⁺ and Ca²⁺ ions. The loaded ZrGP with metallic ions can be efficaciously regenerated by aqueous solution of HCl (1.0 M) without any noticeable capacity loss, and almost all of it can be reused and recycled. The memory effect on structural regeneration of ZrGP was also found when Mg²⁺ and Ca²⁺ were adsorbed. To be specific, the structure of ZrGP was destroyed due to adsorbing these two ions, but it could be regenerated after the loaded materials were dipped in HCl solution (1.0 M) for several minutes to remove metallic ions.     

Cadmium and lead ions can be removed simultaneously from a binary aqueous solution by the sono-sorption method

This paper presents the effect of ultrasound on the simultaneous removal of Cd²⁺ and Pb²⁺ ions from a binary aqueous solution in the presence of natural sorbent (sono-sorption method). The obtained results compare with the results of control method which was achieved in the absence of ultrasound. The experiments under sonication were carried out by 20 kHz apparatus. The effect of different parameters such as the amount of sorbent, contact time, temperature, and specially the competitive sorption of ions were considered for both methods. It is found that the sorption efficiency of Cd²⁺ was decreased in the presence of Pb²⁺. But, the presence of Cd²⁺ had a negligible effect on the removal of Pb²⁺. The results show that in the binary solution, the removal efficiency was higher in the presence of ultrasound than the control method. Both ions in binary solution can be removed to near completion with ultrasound. Two different multi-component isotherm equations based on the Langmuir isotherm were applied on the studied system to predict the sorption behavior of the components.     

Synthesis of magnetic γ-Fe2O3-based nanomaterial for ultrasonic assisted dyes adsorption: Modeling and optimization

γ-Fe₂O₃ nanoparticles were synthesized and loaded on activated carbon. The prepared nanomaterial was characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transforms infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The γ-Fe₂O₃ nanoparticle-loaded activated carbon (γ-Fe₂O₃-NPs-AC) was used as novel adsorbent for the ultrasonic-assisted removal of methylene blue (MB) and malachite green (MG). Response surface methodology and artificial neural network were applied to model and optimize the adsorption of the MB and MG in their individual and binary solutions followed by the investigation on adsorption isotherm and kinetics. The individual effects of parameters such as pH, mass of adsorbent, ultrasonication time as well as MB and MG concentrations in addition to the effects of their possible interactions on the adsorption process were investigated. The numerical optimization revealed that the optimum adsorption (>99.5% for each dye) is obtained at 0.02 g, 15 mg L⁻¹, 4 min and 7.0 corresponding to the adsorbent mass, each dye concentration, sonication time and pH, respectively. The Freundlich, Langmuir, Temkin and Dubinin–Radushkevich isotherms were studied. The Langmuir was found to be most applicable isotherm which predicted maximum monolayer adsorption capacities of 195.55 and 207.04 mg g⁻¹ for the adsorption of MB and MG, respectively. The pseudo-second order model was found to be applicable for the adsorption kinetics. Blank experiments (without any adsorbent) were run to investigate the possible degradation of the dyes studied in presence of ultrasonication. No dyes degradation was observed.     

ESR detection of pressure-induced structural change around Pb2+ and Cd2+ in soda borate glasses

The pressure-induced changes in the coordination structure of Cd²⁺ and Pb²⁺ were examined by measuring the ESR spectra of γ-ray-induced Cd⁺ and Pb³⁺ centers. The s-character of the magnetic electron in the centers increased on densification and was estimated from the analysis of the hyperfine absorption due to a ²⁰⁷Pb³⁺ and ¹¹¹Cd⁺ and ¹¹³Cd⁺. The increase in the s-character means that the strength of both Pb²⁺O and Cd²⁺O bonds was reduced upon densification and that the coordination number of Cd²⁺ and Pb²⁺ increased. The coordination sphere of Cd²⁺, which responds more sensitively than that of Pb²⁺ to the change in chemical environments, was more heavily compressed than that of Pb²⁺.     

Screening and optimization of highly effective ultrasound-assisted simultaneous adsorption of cationic dyes onto Mn-doped Fe3O4-nanoparticle-loaded activated carbon

The ultrasound-assisted simultaneous adsorption of brilliant green (BG) and malachite green (MG) onto Mn-doped Fe₃O₄ nanoparticle-loaded activated carbon (Mn-Fe₃O₄-NP-AC) as a novel adsorbent was investigated and analyzed using first derivative spectrophotometry. The adsorbent was characterized using FT-IR, FE-SEM, EDX and XRD. Plackett–Burman design was applied to reduce the total number of experiments and to optimize the ultrasound-assisted simultaneous adsorption procedure, where pH, adsorbent mass and sonication time (among six tested variables) were identified as the most significant factors. The effects of significant variables were further evaluated by a central composite design under response surface methodology. The significance of independent variables and their interactions was investigated by means of the analysis of variance (ANOVA) within 95% confidence level together with Pareto chart. Using this statistical tool, the optimized ultrasound-assisted simultaneous removal of basic dyes was obtained at 7.0, 0.02 g, 3 min for pH, adsorbent mass, and ultrasonication time, respectively. The maximum values of BG and MG uptake under these experimental conditions were found to be 99.50 and 99.00%, respectively. The adsorption process was found to be followed by the Langmuir isotherm and pseudo-second order model using equilibrium and kinetic studies, respectively. According to Langmuir isotherm model, the maximum adsorption capacities of the adsorbent were obtained to be 101.215 and 87.566 mg g⁻¹ for MG and BG, respectively. The value of apparent energy of adsorption obtained from non-linear Dubinin–Radushkevich model (4.348 and 4.337 kJ mol⁻¹ for MG and BG, respectively) suggested the physical adsorption of the dyes. The studies on the well regenerability of the adsorbent in addition to its high adsorption capacity make it promising for such adsorption applications.     

Spectrophotometric Study of Zinc,Cadmium and Lead Complexes with Murexide in Binary Ethanol-Water Mixtures

The complexation reactions between murexide and Zn²⁺, Cd²⁺ and Pb²⁺ ions in C₂H₅OH-H₂ mixtures have been investigated spectrophotometrically. Formation constants of the resulting 1:1 complexes were determined and found to vary in the order Pb²⁺ > Cd²⁺ > Zn²⁺, in all binary ethanol-water mixtures used. There is an inverse relationship between the complex formation constants and amount of water in the mixed solvent. A linear relationship was observed between log K_f for complexes and the mole fraction of ethanol.     

Adsorption and solid phase extraction of 8-hydroxyquinoline from aqueous solutions by using natural bentonite

The nitrogen-heterocyclic compound 8-hydroxyquinoline (8HQ) is one of the components of coal tar and has a wide variety of uses in industry. Because of its toxicity for aquatic organisms and harmful effects for human health, the removal of 8HQ from aqueous solutions by adsorption onto natural bentonite was investigated in the present work. The experimental results show that the optimum pH value of 2.5 is favourable for the 8HQ adsorption. The experimental data were fitted well with the pseudo-second-order kinetic and Langmuir adsorption isotherm models at all studied temperatures. The maximum adsorption capacity obtained from the Langmuir isotherm model at 20 °C was 120.6 mg g⁻¹. The calculated thermodynamic results such as ΔG° (−24.3 kJ mol⁻¹) and ΔH° (−9.56 kJ mol⁻¹) indicate that the adsorption process is spontaneous and exothermic in nature. Solid phase extraction of 8HQ was also performed. The X-ray diffractometry (XRD), Fourier Transform Infrared (FTIR) and thermogravimetric (TG) analyses were carried out in order to confirm the 8HQ adsorption onto bentonite. According to the obtained results, natural bentonite can be a reusable and effective adsorbent for the removal of 8HQ.     

Optimization of simultaneous ultrasound assisted toxic dyes adsorption conditions from single and multi-components using central composite design: Application of derivative spectrophotometry and evaluation of the kinetics and isotherms

Present study is devoted on the efficient application of Sn (O, S)-NPs -AC for simultaneous sonicated accelerated adsorption of some dyes from single and multi-components systems. Sn (O, S) nanoparticles characterization by FESEM, EDX, EDX mapping and XRD revel its nano size structure with high purity of good crystallinity. Present adsorbent due to its nano spherical shape particles with approximate diameter of 40–60 nm seems to be highly effective in this regard. The effects of five variables viz. pH (3.5–9.5), 0.010–0.028 g of adsorbent and 0.5–6.5 min mixing by sonication is good and practical conditions for well and expected adsorption of MB and CV over concentration range of 3–15 mg L⁻¹. Combination of response surface methodology (RSM) based on central composite design (CCD) and subsequent of analysis of variance (ANOVA) and t-test statistics were used to test the significance of the independent variables and their interactions. Regression analysis reveal that experimental data with high repeatability and efficiency well represented by second-order polynomial model with coefficient of determination value of 0.9988 and 0.9976 for MB and CV, respectively following conditions like pH 8.0, 0.016 g adsorbent, 15 mg L⁻¹ of both dyes 4 min sonication time is proportional with achievement of experimental removal percentage of 99.80% of MB and 99.87% of CV in batch experiment. Evaluation and estimation of adsorption data with Langmuir and Freundlich isotherm well justify the results based on their correlation coefficient and error analysis confirm that Langmuir model is good model with adsorption capacity of 109.17 and 115.34 mg g⁻¹ in single system and 95.69 and 102.99 mg g⁻¹ in binary system for MB and CV, respectively. MB and CV kinetic and rate of adsorption well fitted by pseudo-second order equation both in single and binary systems and experimental results denote more and favorable adsorption of CV than respective value in single system. The pseudo-second-order rate constant k₂ in binary system larger than single system.     

Thermodynamic and kinetic parameters of ciprofloxacin adsorption onto modified coal fly ash from aqueous solution

Batch adsorption experiments were carried out for the removal of ciprofloxacin from aqueous solution using modified coal fly ash as adsorbent. The effects of various parameters such as contact time, initial solution concentration and temperature on the adsorption system were investigated. The optimum contact time was found to be 100 min. The isotherm adsorption data fit well with the Langmuir model, and the kinetic data fit well with the pseudo-second order and the intra-particle diffusion model. Intra-particle diffusion analysis demonstrates that ciprofloxacin diffuses quickly among the particles at the beginning of the adsorption process, and then the diffusion slows down and stabilizes. Thermodynamic parameters such as ΔG, ΔH and ΔS were also calculated. The negative Gibbs free energy change and the positive enthalpy change indicated the spontaneous and endothermic nature of the adsorption, and the positive entropy change indicated that the adsorption process was aided by increased randomness.     

New dithiacrown–ether butadienyl dyes: synthesis,structure, and complex formation with heavy metal cations

Benzothiazole type butadienyl dyes containing a dithia‐15‐crown‐5 ( 2a ) or dithia‐18‐crown‐6 ether ( 2b ) moieties were synthesized. The structures of dyes 2a , b and their complexes with Ag⁺ and Pb²⁺ were studied by an X‐ray crystallography. It was found that the conformations of dithiacrown–ether moieties of dyes 2a , b are unfavorable for complex formation and change significantly upon binding of Ag⁺ or Pb²⁺. The complexation of 2a , b with Ag⁺, Cd²⁺, Pb²⁺, and Hg²⁺ in water–acetonitrile mixtures with different contents of water (P_W = 0–75%, v/v) was studied by ¹H NMR, UV–Vis spectroscopy, and polarography. In anhydrous acetonitrile, the stability constants of 1:1 complexes change in the sequence Cd²⁺ < Pb²⁺ ≤ Ag⁺ << Hg²⁺ in the case of 2a and in the sequence Cd²⁺ < Ag⁺ < Pb²⁺ << Hg²⁺ in the case of 2b . As P_W increases, the thermodynamic stability of Ag⁺ complexes increases. The opposite effect is observed for the complexes with Cd²⁺, Pb²⁺, and Hg²⁺. When P_W ～ 50%, the stability constants of complexes with Cd²⁺ and Pb²⁺ become too small to be measured. The selectivity of ligands 2a , b toward Hg²⁺ versus Ag⁺ is very high at any P_W values (selectivity coefficients > 10⁴). The complexation of 2a , b with Hg²⁺ at P_W ≤ 50% is accompanied by a substantial hypsochromic effect. This allows dithiacrown‐containing butadienyl dyes to be used as selective optical molecular sensors for heavy metal ions, in particular, in aqueous solutions. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis of graphene oxide-poly(2-hydroxyethyl methacrylate) composite by dispersion polymerization in supercritical CO2: adsorption behavior for the removal of organic dye

The use of a biocompatible and thermoresponsive polymer, poly(2-hydroxyethyl methacrylate) (PHEMA) grafted onto the surface of graphene oxide (GO) as an adsorbent for the removal of a cationic dye (methylene blue [MB]) from an aqueous solution is examined in this work. GO–PHEMA forms a hydrogel in water thus overcoming the problem faced by carbon-based adsorbent materials during post-treatment (i.e., separation of adsorbent from the aqueous phase). The GO–PHEMA composite was synthesized using a green approach through dispersion polymerization in supercritical CO₂. The successful preparation of this composite was confirmed by a series of characterization techniques. The adsorption behavior of the composite toward MB such as the effect of the adsorbent dosage, pH, contact time, dye concentration, and recyclability were observed. In addition, the adsorption isotherm, kinetics and thermodynamics were investigated. According to the experimental data, the adsorption parameters were found to fit well into the Freundlich adsorption isotherm with a correlation coefficient of 0.975 and a maximum predicted adsorption capacity of 39.41 mg g^?1 at 25 °C. The adsorption kinetics studies showed that the adsorption behavior followed a pseudo-second-order reaction. On the other hand, the thermodynamics studies showed that the adsorption of MB on GO–PHEMA composite followed spontaneous and endothermic adsorption process with an efficient adsorption temperature at 45 °C. The experimental results also showed that the GO–PHEMA composite could remove 99.8% of the dye in 45 min. Therefore, GO–PHEMA composite is a favorable green adsorbent for environmental applications.     

Highly efficient simultaneous ultrasonic-assisted adsorption of Pb(II), Cd(II), Ni(II) and Cu (II) ions from aqueous solutions by graphene oxide modified with 2,2′-dipyridylamine: Central composite design optimization

In present work, a graphene oxide chemically modified with 2,2′-dipyridylamine (GO-DPA), was synthesized by simple, fast and low-cost process for the simultaneous adsorption of four toxic heavy metals, Pb(II), Cd(II), Ni(II) and Cu(II), from aqueous solutions. The synthesized adsorbent was characterized by FT-IR, XRD, XPS, SEM and AFM measurements. The effects of variables such as pH solution, initial ion concentrations, adsorbent dosage and sonicating time were investigated on adsorption efficiency by rotatable central composite design. The optimum conditions, specified as 8 mg of adsorbent, 20 mg L⁻¹ of each ion at pH 5 and short time of 4 min led to the achievement of a high adsorption capacities. Ultrasonic power had important role in shortening the adsorption time of ions by enhancing the dispersion of adsorbent in solution. The adsorption kinetic studies and equilibrium isotherms for evaluating the mechanism of adsorption process showed a good fit to the pseudo-second order and Langmuir model, respectively. The maximum adsorption capacities (Q_m) of this adsorbent were 369.749, 257.201, 180.893 and 358.824 mg g⁻¹ for lead, cadmium, nickel and copper ions, respectively. The removal performance of adsorbent on the real wastewater samples also showed the feasibility of adsorbent for applying in industrial purposes.     

Synthesis of Tapioca Cellulose-based Poly(amidoxime) Ligand for Removal of Heavy Metal Ions

Poly(acrylonitrile)/cellulose block copolymer (PAN-b-cell) was prepared by using a free radical initiating process and then the nitrile functional groups of the PAN blocks of the copolymers were transformed into amidoxime ligands. The resulting poly(amidoxime) ligands could complex with heavy metal ions; for example, the reflectance spectra of the [Cu -ligand]ⁿ⁺ was found to be at the highest absorbance, about 94%, at pH 6. The pH was the key parameter for metal ions sensing by the ligand. The adsorption capacity for copper was very good, 272 mg g^?1, with a fast adsorption rate (t_1/2 = 10 min). The adsorption capacities for other heavy metal ions such as Fe³⁺, Cr³⁺, Co³⁺ and Ni²⁺ were also good, being 242, 219, 201 and 195 mg g^?1, respectively, at pH 6. The heavy metal ions removal efficiency from water was 98% at low concentration. The data proved that the heavy metal ions adsorption onto the polymer ligands were well fitted with the Langmuir isotherm model (R²>0.99), which suggests that the cellulose-based adsorbent surface namely the poly(amidoxime) ligand, was homogenous and a monolayer. The reusability was examined by a sorption/desorption process for six cycles and the extraction efficiency was determined. This new adsorbent could be reused for 6 cycles without any significant loss in its original removal function.