Application of the electrocoagulation technique for treating heavy metals containing wastewater from the pickling process of a billet plant

This work was carried out to study the removal of various heavy metals, including Cu, Cr, Pb and Zn, from billet industry wastewater by the electrocoagulation process in both batch and continuous experiments at a laboratory scale and ambient temperature (30 °C). In the batch experiment, the effect of various parameters including the current density, initial wastewater pH and electrolysis time, on the metal removal efficiency was examined. Optimal metal ion depletion was attained with a current density of 98 A/m², an initial wastewater pH of 5 and a 30 min electrolysis time. Under these conditions, greater than 99% of Cu, Cr and Zn was removed, whilst the outlet wastewater contained Cu, Cr, Pb and Zn at less than 0.02, 0.01, 0.07 and 0.05 mg/l, respectively. For the continuous process, the results indicated that the treatment system reached its steady state condition within 120 min, and the optimum condition for the continuous treatment was found at an initial wastewater pH of 3 and flow rate of 55 ml/min. At this condition, a complete removal of Cu and Pb and greater than 99% removal of Cr and Zn were achieved.     

Performance evaluation of electrocoagulation process using zinc electrodes for removal of urea

ABSTRACT

This study investigated the ability of the electrocoagulation process to remove urea from synthetic and real wastewater using zinc electrodes. The electrocoagulation cell was operated under various conditions of current density, initial pH, electrode spacing, and electrolytes. The results indicated that the maximum urea removal reached was 66%, which occurred at a current density of 21 mA/cm², initial pH = 7.0, 4 cm electrode spacing, and using magnesium chloride as the electrolyte. By-products were analyzed using FTIR. The anode’s morphology was examined using a scanning electron microscope. Results were compared with chemical coagulation using zinc sulfate as the coagulant.     

Removal of Arsenic from Wastewaters by Airlift Electrocoagulation. Part 1: Batch Reactor Experiments

Abstract

Arsenic removal from wastewater is a key problem for copper smelters. This work shows results of electrocoagulation in aqueous solutions containing arsenic in a newly designed and constructed 1 L batch airlift reactor. Iron electrodes were used in the cell. The airlift electrocoagulation reactor allowed simultaneously a) anodic Fe²⁺ production, b) Fe²⁺ to Fe³⁺ oxidation by air or oxygen, and c) precipitate/coagulate formation due to the turbulent conditions in the cell. A series of electrocoagulation experiments were carried out in the batch airlift reactor. The variables were: initial As(V) concentration, use of either a pure oxygen or an air flow, and electric current density. The results showed that the airlift electrocoagulation process could reduce an initial As concentration from 1000 mg L^?1 to 40 mg L^?1–corresponding to a reduction of 96%. At higher initial concentrations (e.g. 5000 mg L^?1 As) the oxidation of Fe²⁺ to Fe³⁺ seems to be rate determining. Oxidation with compressed oxygen was clearly more efficient than air at high initial As concentration. Arsenate removal from a solution with initially 100 mg L^?1 was efficient with both air and oxygen addition–more than 98% of As precipitated. When the electrocoagulation process was working efficiently, the arsenic removal rate in the cell was found to be around 0.08–0.1 mg As/C. The Fe‐to‐As (mol/mol) ratio, when electrocoagulation was working properly, was in the range of 4–6.     

电絮凝处理含铜电镀废水的研究

通过实验研究了电絮凝处理含铜电镀废水的效果,分别考察了电解时间、电流密度、污染物初始浓度以及pH值的影响,结果表明,pH在中性时,电絮凝对Cu的去除效果好;电流密度增大,污染物去除效果也增大,4 A/dm2的污染物去除效果最好,电解Cu只需10 min就能达到理想的去除效果。初始浓度越大,所需要的通电量越大。     

Comparison of Electrocoagulation and Chemical Coagulation for Heavy Metal Removal

Copper (Cu), chromium (Cr), and nickel (Ni) removal from metal plating wastewater by electrocoagulation and chemical coagulation was investigated. Chemical coagulation was performed using either aluminum sulfate or ferric chloride, whereas electrocoagulation was done in an electrolytic cell using aluminum or iron electrodes. By chemical coagulation, Cu‐, Cr‐, and Ni‐removal of 99.9 % was achieved with aluminum sulfate and ferric chloride dosages of 500, 1000, and 2000 mg L^–1, respectively. Removal of metals by electrocoagulation was affected by the electrode material, wastewater pH, current density, number of electrodes, and electrocoagulation time. Electrocoagulation with iron electrodes at a current density of 10 mA cm^–2, electrocoagulation time of 20 min, and pH 3.0 resulted in 99.9 % Cu‐, 99.9 % Cr‐, and 98 % Ni‐removal.     

Macromolecular Chelator‐Amberlite XAD‐16 Anchored with 2,3‐Dihydroxypyridine (DHP) for Enrichment of Metal Ions before their Determination by Flame Atomic Absorption Spectrometry

Abstract

2,3‐Dihydroxypyridine (DHP) was loaded onto Amberlite XAD‐16 via azo linker and the resulting resin AXAD‐16‐DHP explored for enrichment of Zn(II), Mn(II), Ni(II), Pb(II), Cd(II), Cu(II), Fe(III), and Co(II) in the pH range 4.0–6.5. The sorption capacity was found in the range 120–512 µmol g^?1 and the preconcentration factor from 200 to 300. Tolerance limits for foreign species are reported. The kinetics of sorption is fast, as t_1/2 is generally ≤2 min. The chelating resin can be reused for fifty cycles of sorption‐desorption without any significant change (≤2.0%) in its sorption capacity. The limit of detection values (blank + 3s) are 2.90, 3.80, 5.17, 7.02, 1.91, 1.63, 4.59, and 5.02 µg L^?1 for Zn, Mn, Ni, Pb, Cd, Cu, Fe, and Co respectively. The corresponding limit of quantification (blank + 10 s) values are 5.30, 6.20, 8.38, 9.54, 4.22, 4.17, 8.62, and 9.86 µg L^?1, respectively. The enrichment on AXAD‐16‐DHP coupled with monitoring by flame atomic absorption spectrometry (FAAS) is used to determine these metal ions in river and synthetic water samples, Co in vitamin tablets, and Zn in milk samples. AXAD‐16‐DHP has been found to perform better than DHP loaded cellulose and Amberlite XAD‐2.     

A comparative study of electrocoagulation and electro-Fenton for food industry wastewater treatment: Multiple response optimization and cost analysis

ABSTRACT

In this study, response surface methodology was applied for food wastewater by electrocoagulation (EC) and electro-Fenton (EF) processes. The optimum conditions for the chemical oxygen demand (COD) removal were found to be 21.36 min, pH 10 and 86 mA/cm² in EC, whereas 27.11 min, pH 2.38, 86 mA/cm² and H₂O₂/COD:2 in EF process. COD removal efficiencies were determined to be 29.4% for EC and 59.1% for EF processes and higher than 99% total suspended solids removal efficiencies were achieved. It can be concluded that high COD removal was obtained (4998 mg/L COD removal by EC and 10,047 mg/L COD removal by EF).     

Container washing wastewater treatment by combined electrocoagulation–electrooxidation

Treatment of container washing wastewater (CWW) by using combined electrocoagulation (EC)–electrooxidation (EO) process was studied. CWW contains many organic compounds such as surfactants used in cleaning agents. Wastewater was first treated by EC with iron (Fe) and aluminum (Al) electrodes. The process performance was measured according to the removal efficiencies of soluble chemical oxygen demand (sCOD) and color. Maximum sCOD removal efficiency was found 82% and color removal efficiencies were 95%, 95% and 98% at 436, 525 and 620 nm, respectively, with Fe electrodes under 25 mA/cm² current density, initial pH of 5 and 120-min operation time. Because of the low sCOD removal efficiency, EO was used as post-treatment process by using boron doped diamond electrode (BDD). sCOD removal efficiency was increased to 89% and color removal efficiencies decreased to 72%, 64%, 71% at 436, 525 and 620 nm, respectively, under 25 mA/cm² current density, initial pH of 3 and 300-min operation time. This study showed that electrochemical processes caused new complex molecules formation in the CWW, which caused deterioration of water color and limited the process efficiency.     

Treatment of Endocrine Disrupting Chemical From Aqueous Solution by Electrocoagulation

The removal of endocrine disrupting chemical (BPA; Bisphenol–A) from aqueous solution was experimentally investigated by electrocoagulation process. The effects of different combinations of aluminum (Al) and iron (Fe) electrode pair, supporting electrolyte type, supporting electrolyte concentration, initial pH and applied current density and initial BPA concentration on the Chemical Oxygen Demand (COD), and energy consumption performances were critically evaluated. The experiment results indicate that Al–Al electrode pair is the most efficient choice of the four electrode pairs. The COD removal efficiency was increased when NaCl was used as the supporting electrolyte instead of Na₂SO₄ and NaNO_3. The optimum supporting electrolyte type and its concentration, initial pH, applied current density and treatment time were found to be NaCl, 0.05 M, pH 7.0, 12 mA cm^?2 and 40 min, respectively. Energy consumption was found to decrease with increase of NaCl concentration while it increases with increasing applied current density. The initial and treated sample was characterized by UV–vis spectroscopy to confirm the treatment efficiency. The sludge formed during electrocoagulation was characterized by XRD and SEM/EDAX analysis.     

Separation and recovery of heavy metals from concentrated smelting wastewater by synergistic solvent extraction using a mixture of 2-hydroxy-5-nonylacetophenone oxime and bis(2,4,4-trimethylpentyl) -phosphinic acid

Extraction and separation of copper, zinc, nickel, and cadmium from calcium and magnesium in concentrated smelting wastewater by synergistic solvent extraction using a mixture of 2-hydroxy-5-nonylacetophenone oxime (Mextral 84H) and bis(2,4,4 -trimethylpentyl)-phosphinic acid (Cyanex 272) in an aliphatic diluent (DT-100) was studied. The effects of extractant concentrations, equilibrium pH, organic-to-aqueous phase ratios, system temperature, and extraction and stripping efficiencies on the extraction performance of the heavy metals were investigated. Extraction of pH isotherms showed that addition of Cyanex 272 to Mextral 84H causes obvious synergistic shifts for zinc and cadmium and a slightly antagonistic shift for nickel. The separation factor of cadmium over magnesium was 155.7 and the ΔpH₅₀ values between the metals were over 1.00 pH units. Semi-continuous tests for the metals extraction, scrubbing, and stripping were conducted in a continuous extraction apparatus with conditions further optimized for separation of the metals. Nearly 100% of the copper and nickel and over 98% of the zinc and cadmium were recovered with less than 0.1 mg/L copper and nickel, 26 mg/L of zinc, and 10 mg/L of cadmium remaining in the raffinate. A process in which all valuable metals are extracted simultaneously and stripped selectively at optimal conditions is proposed that is entirely feasible for the separation of copper, zinc, nickel, and cadmium from calcium and magnesium in concentrated smelting wastewater. The study determines the fundamental parameters for the treatment of smelting wastewater by solvent extraction.     

Polymer-Enhanced Crossflow Filtration for Removal of Fe(III), Cu(II), and Cd(II) Ions from Dilute Aqueous Solutions

Abstract

The removal of Fe(III), Cu(II), and Cd(II) ions from aqueous solutions was studied by polymer-enhanced crossflow filtration technique. Alginic acid polymer was used as complexing agents to enhance the retention. Alginic acid/cellulose composite membranes were used in the filtration. In the filtration of metal ion solutions the effects of alginic acid content of the membranes and pH on the percent retention and the permeate flux were examined. The maximum percent retention was found as 98% for 1 × 10^?4 M Fe(III) solution at the flow velocity of 100 mL/min, pH of 3.0, pressure of 60 kPa in the presence of alginic acid as complexing agent by using 0.25 (w/v)% alginic acid/cellulose composite membranes. For 1 × 10^?4 M Cu(II) and Cd(II) solutions the maximum percent retentions were found as 71% and 80% respectively using 0.50 (w/v)% Alginic acid/cellulose composite membranes when the filtration was carried out in the presence of alginic acid at pressure of 10 kPa, flow velocity of 100 mL/min and pH of 7.0.     

Investigation of shipyard wastewater treatment using electrocoagulation process with Al electrodes

In this study, shipyard oily wastewater treatment was investigated by electrocoagulation (EC) using aluminum electrodes in a batch reactor by evaluating different operation conditions. The maximum chemical oxygen demand (COD) removal efficiency of 88.83% was obtained at current density of 3 mA/cm². The removal efficiency was gradually improved with increasing current density and decreased with increasing COD concentration. However, initial pH value was not determinant factor for this process. Total energy and electrode cost were calculated as $0.88 per m³ treated wastewater. The result of this research shows that EC process seems to be an efficient method for the oily wastewater treatment.     

Optimization of the Iron Electro-Coagulation Process of Cr,Ni, Cu,and Zn Galvanization By-Products by Using Response Surface Methodology

An electrocoagulation laboratory scale system was studied for the removal of inorganic pollutants from a mixture of galvanic process-based by-products. Response surface methodology based on a five-level, four-variable central composite rotatable design was employed for optimization with respect to four important variables—reaction time, agitation velocity, current density, and pH. The electrocoagulation process response was evaluated on the basis of chemical oxygen demand (COD), turbidity, total suspended solid, and element concentration values. Interaction effects between reactor operating variables and response variables were evaluated by using 3-D response surface analysis Second-order models were validated by ANOVA. Predicted yields were in a good agreement with the experimental ones. The reactor optimal performance was achieved at 35 min reaction time, 170 rpm agitation velocity, 97.7 Am^?2 current density, and 6.5 initial pH. Under these conditions 100% color and turbidity, 90% COD and total suspended solids, 100% chromium and nickel, and almost 99% zinc and copper were removed. A pseudo-first-order rate model was applied to describe the metal removal kinetics. The EC treatment of heavy metal solutions proved to be more cost-effective than the conventional one, indicating clearly that the method of electro-coagulation is a very promising alternative for industrial applications.     

Biosorption of Heavy Metals by Anoxybacillus gonensis Immobilized on Diaion HP-2MG

Abstract

The determination of trace metal ions usually requires previous separation and preconcentration stages in order to cope with low levels and to remove the interfering components. Nowadays emphasis is given to the utilization of microorganisms because of their great ability to absorb metal ions from aqueous solution. In this paper, for this, Zn²⁺, Fe³⁺, Cu²⁺, Cd²⁺, Ni²⁺, Co²⁺, and Pb²⁺ ions at trace levels have been separated and preconcentrated on a column containing a bacterium, Anoxybacillus gonensis immobilized on Diaion HP-2MG as a new biosorption system prior to their atomic absorption spectrometric determinations. The effects of some analytical parameters were investigated. Optimum pH values were found to be 6 for Zn, Fe, Cu and Pb, 8 for Cd, Ni, and Co. Recoveries of Zn²⁺, Fe³⁺, Cu²⁺, Cd²⁺, Ni²⁺, Co²⁺, and Pb²⁺ were 95 ± 3, 98 ± 6, 96 ± 2, 98 ± 2, 97 ± 2, 95 ± 4 and 95 ± 3 at 95% confidence level, respectively. No significant matrix interferences on the quantitative recoveries of the analyte ions were observed. Preconcentration factors of the anlayte ions were calculated as 50 for Zn, Cd and Pb, and 75 for Fe, Cu, Ni, and Co. The limits of detection for the analyte ions were in the range 0.2–1.3 µg L^?1. The procedure was validated by spike addition and analysis of standard reference materials.     

Removal of Cu(II) and Zn(II) Using Lignocellulosic Fiber Derived from Citrus reticulata (Kinnow) Waste Biomass

Abstract

The biosorption of Cu(II) and Zn(II) using dried untreated and pretreated Citrus reticulata waste biomass were evaluated. The Cu(II) and Zn(II) sorption were found to be dependent on the solution pH, the biosorbent dose, the biosorbent particle size, the shaking speed, the temperature, the initial metal ions (800 mg/L), and the contact time. Twenty-eight physical and chemical pretreatments of Citrus reticulata waste biomass were evaluated for the sorption of Cu(II) and Zn(II) from aqueous solutions. The results indicated that biomass pretreated with sulphuric acid and EDTA had maximum Cu(II) and Zn(II) uptake capacity of 87.14 mg/g and 86.4 mg/g respectively. Moreover, the Langmuir isotherm model fitted well than the Freundlich model with R ² > 0.95 for both metal ions. The sorption of Cu(II) and Zn(II) occurred rapidly in the first 120 min and the equilibrium was reached in 240 min. FTIR and SEM studies were also carried out to investigate functional groups present in the biomass and the surface morphological changes of biomass.     

Adsorption Behavior of Iminodiacetic Acid Type of Chelating Gel Prepared from Waste Paper

Abstract

Adsorption gel was prepared from waste recycled paper by immobilizing iminodiacetic acid (IDA) functional group by chemical modification. The gel exhibited good adsorption behavior for a number of metal ions viz. Cu(II), Pb(II), Fe(III), Ni(II), Cd(II), and Co(II) at acidic pH. The order of selectivity was found to be as follows: Cu(II)>Pb(II)>Fe(III)>Ni(II)～Cd(II)～Co(II). From the adsorption isotherms, the maximum adsorption capacity of the gel for both Cu(II) and Pb(II) was found to be 0.47 mol/kg whereas that for Cd(II) was 0.24 mol/kg. A continuous flow experiment for Cd(II) showed that the gel can be useful for pre‐concentration and complete removal of Cd(II) from aqueous solution.     

Electrochemical Regeneration of Zn-Saturated Granular Activated Carbon from Electroplating Wastewater Plant

An electrically assisted regeneration (EAR) process was used to assess the effectiveness of regenerating exhausted granular activated carbon (GAC) preloaded with electroplating wastewater containing hyper Zn concentration at a concentration of 950.5 mg L ^?1  (1.45 × 10 ^?2  mol L ^?1 ). The electrochemical rege-neration process supplied with direct current was controlled at a constant voltage of 5.0 V. Two regeneration methods were tested and compared: first, acid washing (pH 1.0) and, second, electrically assisted acid washing. Results showed that the Zn adsorption capacity of GAC regenerated by EAR was significantly higher than that of GAC regenerated by acid washing. The effectiveness of the Zn desorbing efficiency from GAC was enhanced by electric current in the electrochemical regeneration process. Using the EAR method, a regeneration efficiency of 88.3% was observed for GAC, whereas using acid regeneration, the efficiency was only 25.3%. These observations reveal that EAR could be a potential alternative to acid washing for the regeneration of GAC saturated with Zn.     

EXTRACTION OF COPPER,CADMIUM AND RELATED METALS WITH POLY(SODIUM ACRYLATE - ACRYLIC ACID)HYDROGELS.

ABSTRACT

The extraction of copper, cadmium and related metals (M²⁺) with poly(sodium acrylate - acrylic acid) PAA hydrogels has been studied. pH variations are consistent with a cation exchange process. Saturation of the gel is achieved for a metal/carboxylate ratio R ≈ 1/2 and a gel swelling of ≈ 40 which is that of the uncharged gel : (-COO)₂M complexes are expected to be formed, but also complexes of higher stoichiometry (R = 1/3 for Cu and Cd, R = 1/4 for Pb) at low metal concentrations. The selectivity is that observed in liquid-liquid extraction of metal cations with fatty carboxylic acids (Pb > Cu > Cd > Zn > Ni ≈ Co). Metal stripping from the gel is readily achieved by washing with 0.1 M HNO₃. PAA hydrogel extraction allows to remove cadmium from a diluted aqueous solution down to a final concentration of 5 ppb.     

Metal ion sorption by chitosan–tripolyphosphate beads

Heavy metal removal from wastewater is crucial for the proper management of discharged water from mining operations. This residual water is typically unusable for other purposes such as for human/animal, crop, or industrial consumption. Eco‐friendly adsorption materials are necessary to ensure the sustainable treatment of this wastewater. Therefore, the sorption of Cu(II), Cd(II), Pb(II), and Zn(II) ions onto chitosan–tripolyphosphate (CTPP) beads was investigated using real mining wastewater and prepared ion metal solutions. The effects of pH, contact time, temperature, selectivity, and maximum sorption capacity in successive batches at different concentrations were studied. The optimum sorption of cations, except for copper (pH 3) was found at pH 5. Equilibrium in the adsorption of all metals was reached at 24 h of contact. Studies of the maximum sorption capacity at different concentrations showed that the CTPP beads could adsorb 158, 55, 47, and 47 mg/g of Pb(II), Cu(II), Cd(II), and Zn(II), respectively. Experimental data for the sorption of Pb(II) were optimally correlated with the Langmuir model. The thermodynamic parameters such as the changes in enthalpy (ΔH⁰), entropy (ΔS⁰), and free energy (ΔG⁰) were determined. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45511.     

Implementation of Hybrid Inorganic/Organic Adsorbents for Removal and Preconcentration of Heavy Metals from Industrial Waste and Drinking Waters

Three hybrid inorganic/organic adsorbents based on alumina and phenylazoformic acid 2-phenylhydrazide were synthesized, characterized and examined for their heavy metal sorption properties. The main purpose of this research paper is to study and explore the combined hybrid characters of inorganic/organic sorbents for the selective removal and preconcentration of heavy metals via static and dynamic solid phase techniques from industrial wastewater and drinking tap water samples as well. The hybrid inorganic/organic adsorbents were identified as strongly resistive to leaching in solutions with pH 1–7 and thermally stable up to 350°C. Optimization of heavy metal removal by implementation of newly designed hybrid inorganic/organic adsorbents was studied in presence of various factors as the effect of pH of contact solution and reaction time via determination of the metal sorption capacity and distribution coefficient. The hybrid adsorbents were successfully implemented for the selective removal of Pb(II), Cu(II), Fe(III), and Cr(III) from industrial wastewater samples with recovery values in the range of 91–99 ± 2–3% as well as 98–99 ± 1–3% for the selective preconcentration of Pb(II), Cu(II), and Cr(III) from drinking tap water samples without noticeable interference caused by the matrix effect.