Synthesis of a carbamide-based dithiocarbamate chelator for the removal of heavy metal ions from aqueous solutions

This study was carried out to develop a carbamide-based dithiocarbamate (CDTC) chelator for the removal of heavy metal ions from wastewater. Its structural properties were characterized by FT-IR, ¹H NMR and ¹³C NMR. Results confirmed the functional groups of HNC(S)S existed. The adsorption isotherms showed CDTC had a high adsorption capability for Zn (119.8 mg/g) and Cu (63.1 mg/g). It exhibited a distinctive selectivity for the removal of metal ions (Cu²⁺ > Zn²⁺ > Cr³⁺ > Pb²⁺ > Cd²⁺) as they coexisted. The influence of initial pH of wastewater for the removal efficiency of metal ions was also investigated and a pH > 7 was preferred.     

Sulfonated multi-walled carbon nanotubes for the removal of copper (II) from aqueous solutions

Sulfonated multi-walled carbon nanotubes (s-MWCNTs) was prepared from purified multi-walled carbon nanotubes (p-MWCNTs) by concentrated H₂SO₄ at elevated temperature. The structure was characterized by SEM, FTIR, Raman, XPS, and BET. It could be dispersed steadily in water at a dosage of 1.0 mg/mL for a week. The adsorption performance of s-MWCNTs toward Cu(II) was investigated including the effects of pH and ionic strength. Results indicated the adsorption was much dependent on pH but not on ionic strength. The adsorption capacity for Cu(II) was enhanced 58.9% via the sulfonation. Moreover, the adsorption mechanisms were carefully analyzed by Freundlich and D-R models.     

Adsorption of some heavy metal ions from aqueous solutions on Nafion 117 membrane

Nafion 117 membrane was investigated for the removal of Ni(II), Co(II), Pb(II), Cu(II) and Ag(I) metal ions from their synthesized aqueous solutions. The different variables affecting the adsorption capacity of the membrane such as contact time, initial metal ion concentration in the feed solution, pH of the sorption medium and temperature of the solution were investigated on a batch sorption basis. The affinity of Nafion 117 membrane towards heavy metal ions was found to increase in the sequence of Cu(II), Ni(II), Co(II), Pb(II), and Ag(I) with adsorption equilibrium achieved after 30 min for all metal ions. Among all parameters, pH has the most significant effect on the adsorption capacity, particularly in the range of 3.1-5.9. The variation of temperature in the range of 25-65 °C was found to have no significant effect on the adsorption capacity. Nafion 117 membrane was found to have high stability combined with repeated regeneration ability and can be suggested for effective removal of heavy metal ions such as Cu(II), Ni(II) and Co(II) from aqueous solutions.     

重金属离子脱除技术进展

综述了脱除水中重金属离子的各类主要方法 ,侧重介绍了近年来开发的若干新技术。     

Calixarene-based extractants for heavy metal ions removal from aqueous solutions

The article reviews the literature on the possibility of application of the calixarene-based compounds for selective separation of toxic heavy metals from aqueous solutions by the solvent extraction and transport across liquid membranes. The specific three-dimensional structure of calixarenes and their derivatives, simple and low-cost synthesis, and ease of chemical transformation qualify these compounds for the role of selective chemical extractants of toxic heavy metal ions present in industrial wastewater. This article analyses the influence of various process factors, with the greatest emphasis on the structure of the extractants/carriers, on efficient separation of heavy metal ions, primarily those most commonly found in galvanic wastewater.     

A study of removal of Pb heavy metal ions from aqueous solution using lignite and a new cheap adsorbent (lignite washing plant tailings)

The present study determines the efficiency with which lignite and lignite washing plant tailings can adsorb Pb heavy metal ions. In the first experiment, the effect of size distribution on the absorbance capacity was investigated for the samples. Therefore, lignite sample was ground to five sizes (d₈₀ = 0.600, 0.355, 0.250, 0.106 and 0.063 mm) under nitrogen (N₂), and the tailings sample was classified into seven fractions, along with the original state (original state: d₆₀ = 0.063, −1 + 0.600, −0.600 + 0.355, −0.355 + 0.250, −0.250 + 0.106, −0.106 + 0.063 and −0.063 mm). The test results showed that the optimum size distributions for lignite and tailings were d₈₀ = 0.063 mm and the original state (d₆₀ = 0.063 mm), respectively. Simultaneously, the adsorption capacity results of the two optimum sizes were compared with each other, and the tailings sample (d₆₀ = 0.063 mm) gave the best results, with 9.30 mg/g Pb ions adsorbed value. Therefore, in the second study, a series of laboratory experiments using 2³ full factorial designs was conducted to determine the optimum pH, contact time and initial metal concentration using the original tailings sample. The experimental studies showed that pH 9, a 120 min contact time and 300 ppm initial metal concentration gave the best results, namely an adsorption of 29.92 mg Pb ions/g.     

The use of exhausted olive cake ash (EOCA) as a low cost adsorbent for the removal of toxic metal ions from aqueous solutions

The removal characteristics of cadmium (Cd(II)) and nickel (Ni(II)) ions from aqueous solution by exhausted olive cake ash (EOCA) were investigated under various conditions of contact time, pH, initial metal concentration and temperature. Batch kinetic studies showed that an equilibrium time of 2 h was required for the adsorption of Ni(II) and Cd(II) onto EOCA. Equilibrium adsorption is affected by the initial pH (pH₀) of the solution. The pH₀ 6.0 is found to be the optimum for the individual removal of Cd(II) and Ni(II) ions by EOCA. The adsorption test of applying EOCA into synthetic wastewater revealed that the adsorption data of this material for nickel and cadmium ions were better fitted to the Langmuir isotherm since the correlation coefficients for the Langmuir isotherm were higher than that for the Freundlich isotherm. The estimated maximum capacities of nickel and cadmium ions adsorbed by EOCA were 8.38 and 7.32 mg g⁻¹, respectively. The thermodynamic parameters for the adsorption process data were evaluated using Langmuir isotherm. The free energy change (ΔG°) and the enthalpy change (ΔH°) showed that the process was feasible and endothermic respectively. As the exhausted olive cake is discarded as waste from olive processing, the adsorbent derived from this material is expected to be an economical product for metal ion remediation from water and wastewater.     

A nanoporous adsorbent for removal of furfural from aqueous solutions

The adsorption of furfural by a surfactant-containing nanoporous material is investigated in the present study. We used cetyltrimethylammonium bromide (CTAB) as the cationic surfactant for synthesis of MCM-48. Batch adsorption studies demonstrate that the surfactant-containing MCM-48 has a significant capacity for adsorption of furfural from aqueous solution. The parameters investigated in this study included pH, contact time, agitation speed and initial furfural concentration. The adsorption process of furfural is tested with Langmuir and Freundlich isotherm models. Application of the Langmuir isotherm to the systems yielded maximum adsorption capacity of 196.1 mg/g.     

Adsorption characteristics of a novel ceramsite for heavy metal removal from stormwater runoff

Urban sediments have rapidly increased in recent years around the world,and their effective management has become an important problem.To remove heavy metals from stormwater runoff and use sediments as a resource,a novel ceramsite was developed using sewer pipe sediments(SPS),river bed sediments(RBS),urban water supply treatment sludge(WSTS),and wastewater treatment plant excess sludge(WWTS).The optimal composition was determined based on the Brunauer–Emmett–Teller specific surface area and an orthogonal test design.The adsorption characteristics of the novel ceramsite for dissolved heavy metals(Cu~(2+)and Cd~(2+)) were investigated through adsorption isotherms and kinetic experiments at(25±1)℃.Both Cu~(2+) and Cd~(2+) were effectively removed by the novel ceramsite,and their equilibrium adsorption was 4.96 mg·g~(-1) and 3.84 mg·g~(-1),respectively.Langmuir isotherms and a pseudo-first-order kinetic equation described the adsorption process better than other techniques.Characterization analysis of the ceramsite composition before and after heavy metal adsorption showed that the Cu~(2+) and Cd~(2+) contents in the ceramsite increased after adsorption.The results revealed that adsorption is both a physical and chemical process,and that ceramsite can be used as a bioretention medium to remove heavy metals from stormwater runoff while simultaneously converting problematic urban sediments into a resource.     

Sorption studies of heavy metal ions on pectin-nano-titanium dioxide composite adsorbent

The Cu(II), Cd(II), Zn(II), and Pb(II) sorption kinetics and equilibrium on hybrid material, composed of pectin and titanium dioxide nanopowder, were examined. Parameters, such as pH and adsorbent dose, were also investigated. The experimental data were better described by the Langmuir model. The maximum adsorption capacities were 1.37, 0.68, 0.51, and 0.83 mmol/g for Cu(II), Cd(II), Zn(II), and Pb(II), respectively. The introduction of nano-TiO₂ improved the kinetics of the metal ion sorption. The titanium dioxide, despite its small content (6%), contributes to the removal of the examined metal ions and eventually to the adsorption capacity of hybrid beads.     

Adsorption of heavy metal cations from aqueous solutions by wool fibers

Adsorption of metal cations by kivircik wool from aqueous NiCl₂, CuCl₂, ZnCl₂, CdCl₂, HgCl₂ and Pb(NO₃)₂ solutions at 25°C and 50°C was investigated using atomic absorption spectroscopy. A fiber diffusion controlled adsorption rate model was used to predict the effective diffusion coefficients of metal ions in wool. It has been shown that wool is a potential adsorbent for removing toxic metal ions from contaminated water.     

Adsorption capacity and removal efficiency of heavy metal ions by Moso and Ma bamboo activated carbons

In order to understand the adsorption capacity and removal efficiency of heavy metal ions by Moso and Ma bamboo activated carbons, the carbon yield, specific surface area, micropore area, zeta potential, and the effects of pH value, soaking time and dosage of bamboo activated carbon were investigated in this study. In comparison with once-activated bamboo carbons, lower carbon yields, larger specific surface area and micropore volume were found for the twice-activated bamboo carbons. The optimum pH values for adsorption capacity and removal efficiency of heavy metal ions were 5.81–7.86 and 7.10–9.82 by Moso and Ma bamboo activated carbons, respectively. The optimum soaking time was 2–4 h for Pb²⁺, 4–8 h for Cu²⁺ and Cd²⁺, and 4 h for Cr³⁺ by Moso bamboo activated carbons, and 1 h for the tested heavy metal ions by Ma bamboo activated carbons. The adsorption capacity and removal efficiency of heavy metal ions of the various bamboo activated carbons decreased in the order: twice-activated Ma bamboo carbons > once-activated Ma bamboo carbons > twice-activated Moso bamboo carbons > once-activated Moso bamboo carbons. The Ma bamboo activated carbons had a lower zeta potential and effectively attracted positively charged metal ions. The removal efficiency of heavy metal ions by the various bamboo activated carbons decreased in the order: Pb²⁺ > Cu²⁺ > Cr³⁺ > Cd²⁺.     

Adsorption of heavy metal ions from aqueous solutions by porous polyacrylonitrile beads

The adsorption of Cu(II), Ni(II), Zn(II), and Pb(II) from aqueous solutions on acrylonitrile copolymer sorbents was studied. We prepared five types of sorbents from polyacrylonitrile by varying its concentration in the initial polymer solution and the composition of the coagulation bath, aiming to achieve a different porous structure. The specific area, pore volume, and pore radius of the sorbents were determined on a porosimeter. The porous structure was studied by scanning electron microscopy. Modification of sorbents with sodium hydroxide and hydroxylamine was carried out to form amidooxyme and carboxylic groups with proven complex‐forming properties toward heavy metal ions. The optimal pH of the sorption of metal ions was found. The adsorption kinetics were investigated. The order of polymer sorbents toward the sorption of Pb(II), Cu(II), Ni(II), and Zn(II) ions, and the order of heavy metal uptake were determined for all types of sorbents. The effectiveness of heavy metal desorption and the coefficient of recovery of sorption ability were determined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3036–3044, 2002; DOI 10.1002/app.2334     

Adsorption characteristics of construction waste for heavy metals from urban stormwater runoff☆

Stormwater runoff has become an important source of surface water pollution. Bioretention, a low impact devel-opment measure in urban stormwater management, has been proven to be effective in the removal of pol utants from stormwater runoff, with appropriate bioretention media. In this study, construction wastes were selected as bioretention media to remove heavy metals from stormwater runoff. Static and dynamic adsorption batch exper-iments were carried out to investigate the adsorption of heavy metals in simulated stormwater runoff system with construction wastes in different particle sizes. The experimental results show that the pseudo-second-order kinetic model characterizes the adsorption process and the adsorption equilibrium data are wel described by Freundlich isotherm model. The construction wastes used can remove heavy metals from stormwater runoff effectively, with their average removal rates al more than 90%. The particle size of construction wastes greatly influences the equilibrium time, rate and adsorption capacity for heavy metals.     

Adsorption isotherms,kinetic, and desorption studies on removal of toxic metal ions from aqueous solutions by polymeric adsorbent

Adsorption of Cd(II), Co(II), and Ni(II) on aminopyridine modified poly(styrene‐alt‐maleic anhydride) crosslinked by 1,2‐diaminoethane as an ion exchange resin has been investigated in aqueous solution. Adsorption behavior of these metal ions on the resin was studied by varying the parameters such as pH (2–6), adsorbent dose (0–4.0 g/L), contact time (0–240 min), and metal ions concentration (20–300 mg/L). Adsorption percentage was increased by increasing each of these parameters. The isotherm models such as: Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich were used to describe adsorption equilibrium. The results showed that the best fit was achieved with the Langmuir isotherm equation, yielding maximum adsorption capacities of 81.30, 49.02, and 76.92 mg/g for Cd(II), Co(II), and Ni(II), respectively. The pseudo‐first‐order, pseudo‐second‐order, and intra‐particle diffusion kinetics equations were used for modeling of adsorption data and it was shown that pseudo‐second‐order kinetic equation could best describe the adsorption kinetics. The intra‐particle diffusion study revealed that external diffusion might be involved in this case. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41642.     

Potential of carbon nanomaterials for removal of heavy metals from water

Heavy metals, such as, cadmium, lead, nickel and zinc can be removed from water using sorbents. The rate and extent of removal may be enhanced by choice of appropriate sorbents. In this study heavy metal sorption was studied on indigenously synthesized carbon nanomaterials (CNMs). Two CNMs differing in surface morphology were synthesized using turpentine oil in a chemical vapour deposition (CVD) setup by varying the process parameters. Activation and catalyst removal were achieved by post-treatment with HNO₃ and KOH. Characterization of the CNMs produced revealed that both comprised of graphitic amorphous carbon, however, while the nanocarbon (NC) produced using cobalt catalyst in N₂ atmosphere comprised of varying grain sizes indicative of soot, the nanoporous carbon (NPC) produced using silica catalyst in H₂ atmosphere had a distinctive uniformly porous surface morphology. Comparative sorption studies with cadmium, lead, nickel and zinc also revealed greater sorption on NPC compared to NC. Batch isotherms for the various heavy metals using NPC and a commercial activated carbon (AC) widely used for metal sorption revealed that NPC is characterized by significantly higher metal sorption capacity and more favourable sorption energetics. The superior performance of NPC as a sorbent may be due to its unique nanoporous structure.     

New modified poly (ethylene terephthalate) (MPET)-based adsorbent for heavy metal ions

Modified poly(ethylene terephthalate) (MPET) samples of both powder and fiber types, which contain sodium 5-sulfodimethyl isophthalate as the third comonomer component, were explored as an adsorbent for the elimination of heavy metal ions, e.g., Cr³⁺, Pb²⁺, and Cd²⁺, in wastewater. The ions were preferentially adsorbed on finer particles at a lower temperature and pH 4 and were exothermically chemisorbed onto the MPETs via an ionic interaction. It was also found that among the ions Cr³⁺ is the most preferentially adsorbed, followed by Pb²⁺ and Cd²⁺ ions and the adsorption capability of MPETs increased considerably with the presence of phenol. The separation factor indicated that the MPET fiber wastes may possibly be reutilized as an economical adsorbent for heavy metal ions in wastewater.     

Sorption of heavy metal ions from aqueous solutions in the presence of EDTA on monodisperse anion exchangers

Conventional precipitation methods of industrial sewage and wastewater purification are not very effective and are insufficient in many cases. This implies the necessity of searching new, effective methods exploiting cheap, accessible and ecologically safe ion exchangers and sorbents. The paper presents the studies on removal of heavy metal ions — Cu(II), Zn(II), Co(II), Ni(II) and Fe(III) — from aqueous solutions in the presence of EDTA carried out on commercially available, strongly basic monodisperse anion exchangers with the polystyrene skeleton gel, Lewatit MonoPlus M 500; and the macroporous, Lewatit MonoPlus MP 500, which are more widely applied in water purification processes. The research results indicate a high affinity of the Lewatit MonoPlus M 500 and Lewatit MonoPlus MP 500 anion exchangers in the chloride form for copper(II), nickel(II), cobalt(II) and zinc(II) complexes with EDTA. The affinity series for the heavy metal complexes in the 0.001 M M(II)/(III)–0.001 M EDTA and 0.001 M M(II)/(III)–0.001M EDTA–0.001 M–0.002 M NaOH systems were found for the Lewatit MonoPlus M 500 anion exchanger in the chloride form to be as follows: Cu(II) > Ni(II) > Co(II) > Zn(II) Fe(III). In the case of the Lewatit MonoPlus MP 500 anion exchanger in the chloride form there was found the following affinity series: Cu(II) > Co(II) > Ni(II) > Zn(II) Fe(III). These anion exchangers can be applied in the removal of copper(II) complexes from waters and wastewaters.     

Adsorption performance of Al-pillared bentonite clay for the removal of cobalt(II) from aqueous phase

In this research, the natural bentonite clay collected from Ashapura Clay Mines, Gujarat State, India, was utilized as a precursor to produce aluminium-pillared bentonite clay (Al-PILC) for the removal of cobalt(II) [Co(II)] ions from aqueous solutions. The original bentonite clay and Al-PILC were characterized with the help of chemical analyses, methylene blue (MB) adsorption isotherm, powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared spectroscopy (IR), while the thermal stability of the samples were studied using thermogravimetry (TG). Surface charge density of the samples as a function of pH was investigated using potentiometric titrations. Adsorption experiments were conducted under various conditions, i.e., pH, contact time, initial concentration, ionic strength, adsorbent dose and temperature. The most effective pH range for the removal of Co(II) ions was found to be 6.0–8.0. The maximum adsorption of 99.8% and 87.0% took place at pH 6.0 from an initial concentration of 10.0 and 25.0 mg l⁻¹, respectively. Kinetic studies showed that an equilibrium time of 24 h was needed for the adsorption of Co(II) ions on Al-PILC and the experimental data were correlated by either the external mass transfer diffusion model for the first stage of adsorption and the intraparticle mass transfer diffusion model for the second stage of adsorption. The intraparticle mass transfer diffusion model gave a better fit to the experimental data. The Arrhenius and Eyring equations were applied to the data to determine the kinetic and thermodynamic parameters for explaining the theoretical behaviour of the adsorption process. The equilibrium isotherm data were analyzed using the Langmuir, Freundlich and Scatchard isotherm equations and the adsorption process was reflected by Freundlich isotherm. The efficiency of the Al-PILC was assessed by comparing the results with those on a commercial ion exchanger, Ceralite IRC-50. The suitability of the Al-PILC for treating Co(II) solutions was tested using simulated nuclear power plant coolant samples. Acid regeneration was tried for several cycles with a view to recover the adsorbed Co(II) and also to restore the adsorbent to its original state.     

Simultaneous removal of humic acid and heavy metal from aqueous solutions using charged ultrafiltration membranes

Lab-made negatively charged ultrafiltration (UF) membranes were used for simultaneous removal of humic acid (HA) and heavy metals from water. Effects of the HA/metal ratio, solution pH and ionic strength on rejection coefficients of HA and metals were investigated. The results showed that the rejection coefficients of both HA and metals increase with the increase of pH and the HA/metal ratio, and the decrease of ionic strength. This study indicated that charged UF could be an effective method for the simultaneous removal of HA and heavy metal harnessing the principle of complexation UF and electrostatic repulsion between the membrane and the HA–M complex of the same charges.