Use of three types of magnetic biochar in the removal of copper(II) ions from wastewaters

Three types of magnetic biochars (MBC1, MBC2, and MBC3) were synthesized from biochar using NaBH₄ as a reducing agent of Fe(II) to Fe(0) to remove copper(II) ions from different wastewaters. Based on the research it was found that removal of copper(II) ions by MBC1 occurs with a yield of 99.8% for the concentration 50 mg/dm³ and decreases to 71.7% at 200 mg/dm³. The maximum pH sorption was found at pH 5. The highest correlation coefficient values (65.55 mg/g) were obtained for the Langmuir isotherm model. Application of 0.5 mol/dm³ HNO₃ as a desorbing agent gives the highest desorption percentage 98.92%.     

Adsorption of Cd(II) ions at the hydroxyapatite/electrolyte solution interface

The study of the Cd(II) ions adsorption at the hydroxyapatite/electrolyte solution interface and the changes of the electrical double layer (EDL) structure in this system are presented. The adsorption of Cd(II) ions was calculated from the loss of their concentration from the solution using the radioisotope method. The adsorption was studied in the range of the initial concentration from 0.000001 to 0.001mol/dm³ and as the function of pH. The results of measurements of Cd(II) ions adsorption kinetics on hydroxyapatite were fitted using the pseudo-first, pseudo-second, and multiexponential modes to check which model describes this process in the best way. In addition, the main properties of the EDL, i.e., surface charge density and zeta potential were determined by the potentiometeric titration and electrophoresis measurements, respectively. The adsorption of Cd(II) ions at hydroxyapatite contributed to the increase of the zeta potential and also to the change of the double electrical layer structure.     

Zn(II) ions removal from aqueous solution by Karachi beach sand, a mixed crystal systems

The aim of this research work is to investigate sorption characteristic of beach sand for the removal of Zn(II) ions from aqueous solutions. The sorption of Zn(II) ions by batch dynamic method is carried out using dilute solutions (10⁻⁴ M) of nitric, hydrochloric and perchloric acids along with deionized water and from buffers of pH 2–10. Maximum sorption is noticed from deionized water (88.3%) using 30 min shaking time. Two equations, i.e. Morris–Weber and Lagergren have been tested to track the kinetics of removal process. The Langmuir, Freundlich and Dubinin–Radushkevich (D–R) model are subjected to sorption data to estimate sorption capacity, intensity and energy. The thermodynamic parameters ΔH, ΔS and ΔG are evaluated. The influence of common ions on the sorption of Zn(II) ions is also examined. Some ions reduce the sorption while most of the ions tested have very little effect. It can be concluded that beach sand has potential to remove Zn(II) ions from aqueous solutions at very low concentrations and for the treatment of industrial effluent carrying Zn(II) ions.     

Kinetics of ligand exchange reaction of Cu(II)-ammine complex with poly(vinyl alcohol) in aqueous solution

The kinetics of the ligand exchange reaction of the Cu(II)-ammine complex with poly(vinyl alcohol) (PVA) has been studied by a stopped-flow method at pH 9–10, at μ=0.1 (NH₄Cl) and at 25°C. The reaction is initiated by the formation of unstable [Cu(NH₃)₃]²⁺ by the attack of H⁺ on Cu(II)-ammine complex, and proceeds through the mixed complex {[Cu(NH₃)₃(O?PVA)]²⁺}. This step may be rate-determining, followed by a rapid reaction. Finally, the Cu(II) ion is taken up by PVA. The rate is given by d[Cu(II)?PVA]/dt=k[H⁺]{[Cu(NH₃)₄]²⁺}[PVA]/[NH₄Cl], where k=k₁ + k′₂[H⁺], k₁=4.25× 10s^?1 and k′₂=5.20× 10¹¹l mol^?1s^?1.     

Biosorption of copper (II) from aqueous solutions by wheat shell

The adsorption capacity of wheat shell for copper (II) was studied at various pH (2-7), agitation speeds (50-250 rpm) and initial metal ion concentrations (Co, from 10 to 250 mg.L⁻¹). Maximum biosorption of copper onto wheat shell occurred at 240 rpm agitation speed and at pH between 5 and 6. The biosorption values of copper (11) were increased with increasing pH from 2 to 5 and decreased with increasing copper/wheat shell (x/m) ratios from 0.83 to 10.84 mgCu(II).g⁻¹ wheat shell. The biosorption efficiencies at these x/m ratios were 99% and 52%, respectively, at the end of the 120 min contact time (t). The equilibrium isotherms and kinetics were obtained from batch adsorption experiments at 298 K. It was observed that wheat shell was a suitable biosorbent for removing Cu(II) from aqueous solutions.     

Water purification of removal aqueous copper (II) by as-grown and modified multi-walled carbon nanotubes

This study compares aqueous copper (II) adsorbed onto as-grown and modified carbon nanotubes (CNTs), using H₂SO₄ and H₂SO₄/KMnO₄ processes. H₂SO₄ and H₂SO₄/KMnO₄ modifications reduced pH_iep and Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed that some functional groups were formed on modified CNTs. The adsorption capacity of copper (II) onto modified CNTs was greater than that of as-grown CNTs, especially at pH 6. The results demonstrate that the modified processes increased the adsorption capacity because the functional groups were generated on the modified surfaces of the CNTs. Additionally, the adsorption capacity of copper (II) onto as-grown and modified CNTs both increased with temperature, and the results indicated that the Langmuir isotherm fitted the experimental data well. Simulation results indicated that the ΔH⁰ values of as-grown, H₂SO₄-modified CNTs and H₂SO₄/KMnO₄-modified CNTs were 4.83, 14.37 and 29.92 kJ/mol, respectively. Based on ΔH⁰, the adsorption of Cu²⁺ onto H₂SO₄/KMnO₄-modified CNTs is suggested to proceed simultaneously by physisorption and chemisorption but that onto as-grown and H₂SO₄-modified CNTs may proceed only by physisorption.     

Extraction of Cu(II) ions from aqueous media using PEG/Sulphate salt aqueous two-phase system

A simple ATPS of polyethylene glycol/sulphate salt was proposed for the extraction of Cu(II) ions from aqueous media. Maximum extraction efficiency of Cu ions was obtained in the aqueous PEG2000/ sodium sulphate two-phase system. In the following, design of experimental methodology using Taguchi orthogonal array was applied to evaluate the effects of four independent variables on the partitioning behavior of Cu ions from aqueous media. The results indicated that the temperature and pH of the system were the major contributory factors for Cu ions partitioning. The maximum extraction efficiency of Cu ions was determined to be 77.89% under the optimal conditions.     

Copper(II) removal from aqueous solution by organosolv lignin and its recovery

In this study the removal of Cu(II) ions from aqueous solution was performed at different concentrations, temperatures, and pHs using ethanol‐based organosolv lignin as the adsorbent. The results indicated that the amount of Cu(II) ions adsorbed onto the lignin increased with increasing concentration and pH; however, it decreased with an increase in temperature. It was possible to remove 40.74% (maximum removal) of Cu(II) ions from aqueous solution by using organosolv lignin within 10 min under certain conditions (3 × 10^?4 M and 20°C). The adsorption process was determined to be consistent with the Freundlich isotherm. Furthermore, it was found that 40% (maximum recovery) of the Cu(II) ions adsorbed on the organosolv lignin could be recovered using HCl with an initial concentration of 3 × 10^?4 M and a contact time of 10 min. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1537–1541, 2003     

Arsenic adsorption using copper (II) oxide nanoparticles

Arsenic poisoning is a major problem in today's life. To reduce its concentration in drinking water, different metal based compounds were explored as arsenic adsorbents. In the present study, copper (II) oxide nanoparticles were prepared by thermal refluxing technique and used as an adsorbent for arsenic removal from water. Characterization of the adsorbent using TEM, BET, XRD and FTIR implied that the prepared adsorbent was in nano size and had excellent adsorption behavior with surface area of 52.11 m²/g. Systematic adsorption experiments were carried out with different process parameters such as contact time, adsorbent mass, pH, temperature and stirring speed and found that copper (II) oxide had very good efficiency towards arsenic adsorption. Thermodynamic parameters and adsorption kinetics were studied in detailed to know the nature and mechanism of adsorption. Results showed that the adsorption process followed pseudo second order kinetic and endothermic behavior. Adsorption equilibrium was studied with Langmuir and Freundlich isotherm models. The adsorption process followed Langmuir isotherm with an adsorption capacity of 1086.2 μg/g. A regeneration study was proposed in order to reuse the adsorbent for better economy of the process. Finally, a process design calculation is reported to know the amount of adsorbent required for efficient removal of arsenic from aqueous medium.     

Adsorption of copper(II), cobalt(II), and iron(III) ions from aqueous solutions on poly(ethylene terephthalate) fibers

The adsorption behavior of poly(ethylene terephthalate) (PET) fibers towards copper(II), cobalt(II), and iron(III) ions in aqueous solutions was studied by a batch equilibriation technique. Influence of treatment time, temperature, pH of the solution, and metal ion concentration on the adsorption were investigated. Adsorption values for metal ion intake followed the following order: Co(II) > Cu(II) > Fe(III). One hour of adsorption time was found sufficient to reach adsorption equilibrium for all the ions. The rate of adsorption was found to decrease with the increase in the temperature. Langmuir adsorption isoterm curves were found to be significant for all the ions studied. The heat of adsorption values were calculated as −5, −2.8, and −3.6 kcal/mol for Cu(II), Co(II), and Fe(III) ions, respectively. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1935–1939, 1998     

Chitosan functionalized with 2[-bis-(pyridylmethyl) aminomethyl]4-methyl-6-formyl-phenol: equilibrium and kinetics of copper (II) adsorption

The complexation agent 2[-bis-(pyridylmethyl) aminomethyl]-4-methyl-6-formyl-phenol (HL) was immobilized in chitosan in order to obtain a new adsorbent material to be employed in studies on adsorption and pre-concentration of Cu(II). The chitosan modified by the complexation agent was characterized by infrared spectroscopy, DSC and TGA. The studies were conducted as a function of the pH of the medium and the mechanism of Cu(II) adsorption in the solid phase was analyzed utilizing several kinetic models. The parameters for the adsorption of Cu(II) ions by chitosan-HL were determined with a Langmuir isotherm, the maximum saturation capacity of the monolayer being 109.4 mg of Cu(II) per gram of polymer. Electron paramagnetic resonance spectroscopy revealed that Cu^II ions coordinate to the donor atoms of the HL ligand anchored to the surface of the polymer forming a stable chelate complex in the solid state.     

Optical and electrochemical properties and sensing application for iron(II) and mercury(II) ions of polyfluorenes with imidazole in the main chain

Polyfluorenes bearing imidazole and triphenylamine moieties in the main chain were synthesized. The imidazole/triphenylamine molar ratios in the polymer backbone were 100/0 (PFIM100), 50/50 (PFIM50) and 25/75 (PFIM25). Cyclic voltammetry revealed reversible oxidation only for polymers containing triphenylamine moieties (PFIM50 and PFIM25) and irreversible reduction for all polymers. Optical properties of the polymers were investigated using UV‐visible and photoluminescence spectroscopies in solution. The sensing properties of PFIM100 were investigated. The polymer showed recognition towards two analytes, Fe²⁺ and Hg²⁺. PFIM100 exhibited selective fluorescence ‘turn‐off’ response to Fe²⁺ cations. Interaction of PFIM100 with I^? anions produced a non‐emissive complex. The PFIM100/I^? complex exhibited excellent ‘turn‐on’ sensing properties for detection of Hg²⁺. © 2019 Society of Chemical Industry     

Preparation,characterization, and adsorption properties of chitosan microspheres crosslinked by formaldehyde for copper (II) from aqueous solution

The chitosan microspheres crosslinked by formaldehyde were prepared by spray drying method and used as an adsorbent for copper (II) from aqueous solution. A batch adsorption system was applied to study the adsorption of copper (II) from aqueous solution by chitosan microspheres. The maximum adsorption capacity of the chitosan microspheres for copper (II) was 144.928 mg/g at pH 6.0. Langmuir adsorption model was found to be applicable in interpreting the adsorption process. To elucidate the adsorption mechanism, the chitosan microspheres before and after copper (II) adsorption were further characterized by Fourier transform infrared spectra, zeta potential analysis, and scanning electron microscope. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Studies on the biosorption of Pb(II) ions using Pseudomonas putida

ABSTRACT

The complete removal of Pb(II) was achieved by intact Pseudomonas putida cells. The biosorption isotherm exhibited Langmuirian behaviour and followed pseudo-second-order rate kinetics. The standard Gibbs free energy change (?G°) for the biosorption of Pb(II) ions was found to be ?26.4 kJ mol^?1, attesting to a chemisorption process. Thermolysis of P. putida cells improved the Pb(II) binding capacity by around 27%. All the four components tested, namely DNA, protein, polysaccharide and lipid, were found to contribute to the uptake of Pb(II) ions. The possible mechanisms of Pb(II) binding by P. putida have been delineated.     

Fixed-bed column study on removal of Mn(II), Ni(II) and Cu(II) from aqueous solution by surfactant bilayer supported alumina

In the present work, the potential of modified alumina for the removal of heavy metals such as Mn(II), Ni(II) and Cu(II) was evaluated in a fixed-bed column operation. The effects of bed depth, flow rate and initial concentration on the removal of Mn(II), Ni(II) and Cu(II) were investigated at the optimum pH. The modified alumina was found to be very efficient for the removal of such heavy metals from water environment. Bed depth service time (BDST) model was best fitted to adsorption data. The theoretical and experimental breakthrough curves were comparable for all heavy metals.     

含金属离子赖氨酸水溶液的萃取分离

采用二(2-乙基己基)磷酸(P204)作萃取剂,航空煤油作稀释剂,对含有钙、镁、钠、钾等金属离子的赖氨酸水溶液进行萃取,以蒸馏水作为反萃取剂对有机相进行反萃取分离实验.结果表明,原料液初始pH值在4～5、P204与煤油体积比为3:2、有机相与水相比为2:1、反应萃取时间大于30min、搅拌转速约200rpm时,能够取得较好的萃取效果.以初始pH值≥3.5的蒸馏水为反萃取剂,蒸馏水与有机相体积比4:1,在150rpm的转速下搅拌20min能够较为完全地分离出赖氨酸,然后在其它条件相同的情况下,用初始pH＜1的蒸馏水对有机相再次反萃取可分离出金属离子,从而实现萃取剂的重复利用.     

Novel dicopper(II)-tetracarboxylates as catalysts for selective oxidation of benzyl alcohols with aqueous TBHP

A few dicopper(II) tetracarboxylate complexes viz. [Cu₂(µ-O₂CC₆H₅)₄(4-Etpy)₂] (1), [Cu₂(µ-O₂CC₆H₅)₄(4-DMAP)₂] (2), [Cu₂(µ-O₂CC₆H₅)₄(4-CNpy)₂] (3) and [Cu₂(µ-O₂CCH₃)₄(4-CNpy)₂] (4) have been utilised as catalysts for oxidation of benzyl alcohols using aqueous tert-butyl hydroperoxide as the oxidant. Complexes 1 and 2 have shown better catalytic activity than the other two. Unlike other catalysts, these dicopper complexes can catalyse oxidation of alcohols at a very low concentration (0.5 mol%).