Plating Wastewater Research Articles

Lead(II) removal from aqueous solution using Citrus limettioides peel and its modified form: isotherms, kinetics and thermodynamic studies

The Pb(II) adsorption capacity of carbon derived from Citrus limettioides peel (CLPC), which is a novel waste material, was evaluated regarding the contact time, pH and adsorbent dose during batch adsorption processes with raw C.limettioides peel (CLP). The optimal contact time for the adsorption of Pb(II) ions onto the peel and peel carbon was 3 h, and the optimal pH ranged from 4.0 to 5.0 for CLP and 4.0–6.0 for CLPC, respectively. The equilibrium data fit well with Langmuir isotherm, indicating that the Pb(II) ions formed a homogenous monolayer on the adsorbent surface. Maximum monolayer adsorption capacity of Pb(II) ions on peel (CLP) and peel carbon (CLPC) was found to be 125.00 and 166.67 mg g−1, respectively. The kinetic studies showed that the adsorption data followed a pseudo-second-order kinetic model. The surface morphology and functionality of the CLP and CLPC were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy and FT-IR. Various thermodynamic parameters, including the standard Gibbs free energy (∆G°), standard enthalpy (∆H°) and standard entropy (∆S°), were evaluated. The CLP and CLPC were tested with Pb(II) plating wastewater through a batch mode process over five cycles; CLPC showed better results than CLP.

Operational parameter influence on heavy metal removal from metal plating wastewater by electrocoagulation process

Among the different treatment processes available for industrial wastewater treatment, electrocoagulation represents a challenging option due to several features, such as environmental compatibility, inherent safety, energy and cost effectiveness. The effectiveness of electrocoagulation process (ECP) using aluminium and iron electrodes for the removal of heavy metals from industrial wastewater has been investigated, with particular attention to the effects of operating parameters (pH, inter-electrode distance, hydraulic retention time and current density) on removal efficiency. In the first step of the experimental phase, a laboratory-made artificial wastewater containing heavy metals (Cu, Ni and Pb) was adopted in order to identify the optimum conditions that were subsequently applied to treat a metal plating industrial wastewater. Experimental results revealed that under the optimal experimental conditions (actual pH 6.32, current density 0.026 A cm-2), the removal efficiency of heavy metals from artificial wastewater was higher than 95 %.

희생전극을 이용한 무전해 니켈 도금 폐수의 전기분해처리 최적화

The effluent limit of nickel from electroplating wastewater has been strengthened from 5 mg/L to 3 mg/L from 2014. However, currently applied treatment process for nickel plating wastewater is unable to meet the effluent limit, most of the treatment concept conducted by treatment plant is dilution with other metal bearing wastewater. This can cause very significant impact to the environment of nickel contamination. With this connection, the feasibility test has been conducted with the use of electrolysis by using sacrificial electrodes. Experiments were conducted in synthetic and electroless nickel plating wastewater. Optimal condition of current density, pH were derived from the synthetic wastewater. It was found that the removal efficiency of nickel exceeded 94% at the operation condition of at pH 9 and the current density of 1~2 mA/cm. At this conditions, the iron sludge was generated very low amount. However, it was unsuccessful to meet the effluent limit by applying these treatment conditions to the real electroplating wastewater. This can be explained due to the matrix effect of other metals and anions contained real electroplating wastewater. From the result of further study, the optimal conditions for the real wastewater treatment were found out to be at pH 9, current density 6~7 mA/cm, for 5 minutes of operating time. At these conditions, 88% removal of nickel was achieved, which results the residual nickel concentration was below 3 mg/L.

Simplification and sensitivity study of Alamar Blue bioassay for toxicity assessment in liquid media

Bacteria, as an essential component of most wastewater treatment plants (WWTPs), play a critical role in the biological stage of WWTPs due to their role in cycling mineral compounds and in the decomposition of organic material. In this study, a modified Alamar Blue-based bioassay was used to evaluate the toxicity of metal plating wastewaters on sequence batch reactor (SBR) bacteria. For confirming the robustness, reproducibility, and efficiency of the optimized method, it was compared with the standard colony count protocol and oxygen consumption method. The influence of pH on the Alamar Blue reduction was examined over a pH range of 1.0–13.0. The optimum pH for Alamar Blue bioassay using SBR bacteria was 6.5–7. The correlation between the reduction of Alamar Blue by SBR bacteria and their oxygen consumption coefficient was 0.945. According to our optimized bioassay, Alamar Blue was rapidly reduced by active SBR bacteria. This protocol successfully assessed the toxicity of metal plating wastewaters. As most of the WWTPs are inefficient for elimination of toxic effect of metals, it is desirable to use bioassays that can determine the toxicity of such pollutants. We simplified and optimized such an assay that can be manipulated for real metal plating wastewater samples.

Resazurin reduction assay, a useful tool for assessment of heavy metal toxicity in acidic conditions.

Almost all bioassays have been designed only for pH levels around 7; however, some toxicant characteristics may be different at lower pH values. In this study, a modified resazurin reduction method was used to evaluate the toxicity of heavy metals and metal plating wastewater on acid-tolerant (AT) and conventional bacteria at the natural and acidic pH conditions. According to our optimized protocol, resazurin was rapidly reduced by both conventional and AT active microorganisms. Considering the 30-min median effective concentration (30 min EC₅₀) values, conventional bacteria were comparatively more resistant than the acid-tolerant bacteria (ATB) in the case of exposure to Cd, Pb, Cr, and Zn, but the reverse case was found for Hg. After an exposure of 30 min, Cr and Hg showed the highest toxicity to ATB (30 min EC₅₀ values were 0.34 and 17.02 μmol/L, respectively), while Zn and Pb had a considerably lower toxicity. The modified resazurin reduction method successfully assessed the impact of metal plating wastewaters on the activities of conventional and AT bacteria. According to the findings where the wastewaters contain heavy metals, wastewater treatment facilities, which are dependent on ATB activity, should use bioassays at acidic pH values for better understanding of the effects of toxicants.

Efficient removal of heavy metals from electroplating wastewater using polymer ligands

Poly(hydroxamic acid)-poly(amidoxime) chelating ligands were synthesized from poly(methyl acrylate-co-acrylonitrile) grafted acacia cellulose for removing toxic metal ions from industrial wastewaters. These ligands showed higher adsorption capacity to copper (2.80 mmol·g−1) at pH 6. In addition, sorption capacities to other metal ions such as iron, zinc, chromium, and nickel were also found high at pH 6. The metal ions sorption rate (t1/2) was very fast. The rate of adsorption of copper, iron, zinc, chromium, nickel, cobalt, cadmium and lead were 4, 5, 7, 5, 5, 8, 9 and 11 min, respectively. Therefore, these ligands have an advantage to the metal ions removal using the column technique. We have successfully investigated the known concentration of metal ions using various parameters, which is essential for designing a fixed bed column with ligands. The wastewater from electroplating plants used in this study, having chromium, zinc, nickel, copper and iron, etc. For chromium wastewater, ICP analysis showed that the Cr removal was 99.8% and other metal ions such as Cu, Ni, Fe, Zn, Cd, Pb, Co and Mn removal were 94.7%, 99.2%, 99.9%, 99.9%, 99.5%, 99.9%, 95.6% and 97.6%, respectively. In case of cyanide wastewater, the metal removal, especially Ni and Zn removal were 96.5 and 95.2% at higher initial concentration. For acid/alkali wastewater, metal ions removing for Cd, Cr and Fe were 99.2%, 99.5% and 99.9%, respectively. Overall, these ligands are useful for metal removal by column method from industrial wastewater especially plating wastewater.

Removal of nickel(II) from aqueous solution using Citrus Limettioides peel and seed carbon

The agricultural wastes like Citrus Limettioides peel and seed to be suitable precursor for the preparation of carbon [Citrus Limettioides peel carbon (CLPC) and seed carbon (CLSC)] has been explored in the present work, utilizing sulfuric acid as the activating agent. Adsorption studies were performed by varying contact time, solution pH, adsorbent dose and temperature. The equilibrium time for Ni(II) ions was determined as 4h and optimal pH was 4–7. Surface morphology and functionality of the CLPC and CLSC were characterized by SEM, EDX and FT-IR. The experimental data were analysed using the Freundlich, Langmuir, Temkin, Redlich–Peterson, Sips and Dubinin–Radushkevich adsorption isotherm equations using nonlinear regression analysis. Equilibrium data were found to fit well in the Langmuir isotherm, which confirmed the monolayer coverage of Ni(II) ions. The Langmuir monolayer adsorption capacity of CLPC and CLSC was found to be 38.46 and 35.54mg/g. The thermodynamic parameters indicated that the adsorption process was spontaneous and exothermic in nature. The kinetic data followed pseudo-second order model with film diffusion process. The adsorbents were tested with Ni(II) plating wastewater in connection with the reuse and selectivity of the adsorbents.

Nickel (II) removal using modified Citrus limettioides peel

The Ni(II) adsorption capacity of carbon derived from Citrus limettioides peel (CLP), which is a novel waste material (CLPC), was evaluated regarding contact time, pH and adsorbent dose during batch adsorption processes with raw CLP. The optimal contact time for the adsorption of Ni(II) ions onto the peel and peel carbon was 3 h, and the optimal pH ranged from 5.0 to 8.0 for CLP and 4.0–8.0 for CLPC, respectively. The removal percentage decreased from 85.0 to 70.0 % for CLP and remained nearly constant (99 %) for CLPC when the initial Ni(II) concentration was increased from 10 to 50 mg L−1. The equilibrium data fit the Langmuir isotherm with a high R 2 value, indicating that the Ni(II) ions formed a homogenous monolayer on the adsorbent surface. Adsorption capacity of Ni(II) ions on peel (CLP) and peel carbon (CLPC) was found to be 25.64 and 38.46 mg g−1, respectively. The surface morphology and functionality of the CLP and CLPC before and after adsorption were characterized using SEM, EDX and FT-IR. Various thermodynamic parameters, including the standard Gibbs free energy (∆G°), standard enthalpy (∆H°) and standard entropy (∆S°), were evaluated. The CLP and CLPC were tested with Ni(II) plating wastewater through a batch-mode process over five cycles; CLPC showed better results than CLP.

めっき排水からの有価金属回収

めっき排水からの有価金属回収

Spectrophotometric Determination of Cr(III) and Pb(II) Using Their Complexes with 5,11,17,23-Tetra[(2-ethyl acetoethoxyphenyl)(azo)phenyl]calix[4]arene.

New complexes of 5,11,17,23-tetra[(2-ethyl acetoethoxyphenyl)(azo)phenyl]calix[4]arene (TEAC) with Pb(II) and Cr(III) were prepared in basic solution with a mixture of MeOH and H2O as solvent. The ratio of TEAC and metal ion in complexes was found to be 1 : 1 under investigated condition. The complex formation constants (based on Benesi-Hildebrand method) for TEAC-Pb(II) and TEAC-Cr(III) were 4.03 × 104 and 1.2 × 104, respectively. Additionally, the molar extinction coefficients were 5 × 104 and 1.42 × 104 for TEAC-Pb(II) and TEAC-Cr(III), respectively. The H-Point Standard Addition Method (HPSAM) has been applied for simultaneous determination of complexes formation of Cr(III)/Pb(II) and TEAC with concentration from 2 : 1 to 1 : 20 (w/w). The proposed method was successfully utilized to invest lead and chromium contents in plating wastewater samples. The results for several analyzed samples were found to be in satisfied agreement with those acquired by using the inductively coupled plasma mass spectrometry (ICP-MS) technique.

Simultaneous removal of nickel and phosphorus from spent electroless nickel plating wastewater via calcined Mg–Al–CO3 hydroxides

This picture shows the different adsorption mechanisms of CLDHs for electroless nickel plating wastewater with low and high ionic concentrations.

Kinetics and thermodynamics of zinc removal from a metal-plating wastewater by adsorption onto an Iranian sepiolite

The study of the kinetics and thermodynamics of the adsorption process can provide valuable information for the proper design and control of adsorption systems. The influence of temperature on the kinetics of Zn2+ sorption on an Iranian sepiolite sample was investigated through a series of batch experiments. Consistent with an exothermic reaction, an increase in the temperature resulted in decreasing Zn2+ adsorption rate. The sorption kinetics was tested for pseudo-first-order, pseudo-second-order, and intraparticle diffusion models, and the rate constants were calculated. Results showed that the adsorption kinetics followed the pseudo-second-order kinetic model. The intraparticle diffusion model described that sorption of Zn onto the sepiolite particles is a two-step process, and intraparticle diffusion is not the only rate-limiting step. The results obtained from the study of thermodynamic data indicated that sorption of Zn onto sepiolite is non-spontaneous and less favored at higher temperatures.

Heavy metal ions removal from metal plating wastewater using electrocoagulation: Kinetic study and process performance

• High removal of heavy metal ions from metal plating wastewater using EC treatment. • Pseudo first-order kinetic model describes heavy metal ions removal adequately. • Electrocoagulation time and DC current density are the key parameters in EC process. • Metal plating wastewater treatment by electrocoagulation is economically rewarding. The main objective of the present study was the removal of heavy metal ions, namely Cu 2+ , Cr 3+ , Ni 2+ and Zn 2+ , from metal plating wastewater using electrocoagulation technique. An electro-reactor was used with six carbon steel electrodes of monopolar configurations. Three of the electrodes were designated as cathodes meanwhile the other three as anodes. The results showed that the removal efficiency of heavy metal ions increases with increasing both electrocoagulation (EC) residence time and direct current (DC) density. Over 97% of heavy metal ions were removed efficiently by conducting the EC treatment at current density (CD) of 4 mA/cm 2 , pH of 9.56 and EC time of 45 min. These operating conditions led to specific energy consumption and specific amount of dissolved electrodes of around 6.25 kWh/m 3 and 1.31 kg/m 3 , respectively. The process of metal plating removal using EC consumes low amount of energy, making the process economically feasible and possible to scale up. Moreover, the kinetic study demonstrated that the removal of such heavy metal ions follows pseudo first-order model with current-dependent parameters.

Efficient removal of Cr(VI) from wastewater under sunlight by Fe(II)-doped TiO2 spherical shell

Fe(II)-doped TiO2 spherical shell catalyst was synthesized by one-pot hydrothermal method. The photocatalytic removal of Cr(VI) from plating wastewater under sunlight of the catalyst was demonstrated. It was found that the removal effectiveness of about 99.99% for initial Cr(VI) concentration of 102.3ppm and 99.01% for 153.4ppm under 3h sunlight irradiation is realized. The Fe(II) ions serve not only as reducing agents for reducing the Cr(VI) to Cr(III) but also as an intermedium of a two-step reduction, in which the TiO2 photoreduces the Fe(II) ions to Fe atoms firstly, and then the Fe atoms reduce the Cr(VI) to Cr(III). The improved photocatalytic activity of the catalyst is considered due to the synergistic effect of a multi reducing process by Fe(II) doping. The extended optical response and effectively utilization of sunlight of the special spherical-shell-like morphology also contribute to the enhanced photocatalytic activity.

Feasibility of Combining Reverse Osmosis–Ferrite Process for Reclamation of Metal Plating Wastewater and Recovery of Heavy Metals

The feasibility of reverse osmosis (RO) separation combined with ferrite reaction was investigated for the reclamation and recovery of heavy metals from metal plating wastewater. Disc tube-type RO modules were used for simultaneous purification and concentration of wastewaters containing zinc and chromium ions. A subsequent ferrite reaction was performed to recover zinc ions from RO concentrates. The operating conditions of the RO and ferrite reaction were determined in several lab-scale experiments with several types of model wastewater. Pilot-scale RO test results revealed that the zinc plating wastewater treated by one-pass RO and the chrome plating wastewater treated by two-pass RO were acceptable for preplating rinsewater. After ferrite reaction, 99.7% of zinc ions were recovered from the second-stage RO concentrate in the form of zinc ferrite, while significant amounts of chromium ions were retained in the concentrate. As a result of economic analysis, we suggested a retrofitting option, including a...

Removal of Chromium by Coagulation-Dissolved Air Flotation System Using Ferric Chloride and Poly Aluminum Chloride (PAC) as Coagulants

In this study, dissolved air flotation (DAF) was examined as a possible treatment method for the removal of chromium from aqueous solution and plating wastewater. Two coagulants, ferric chloride and poly aluminum chloride (PAC), were used for pretreatment of wastewater. Maximum removal of chromium was achieved for poly aluminum chloride (98 %). Artificial neural network was used for the prediction of the DAF system. The best neuron used for the prediction of chromium removal percentage of interpolated wastewater was 6 %. The mean score error and the coefficient correlation were 0.0007542 and 0.997, respectively.

Photovoltaic electrocoagulation process for remediation of chromium plating wastewaters

The proposed photovoltaic electrocoagulation (PV-EC) process combines the autonomous and environmentally friendly photovoltaic (PV) solar energy with the capability of iron electrocoagulation (EC) to effectively reduce both trivalent and hexavalent chromium ions from electroplating effluents. The PV array can be connected directly to the EC reactor without batteries increasing, in this way, the system sustainability and eliminating the environmental threat of improper battery disposal. The PV-EC system is made versatile according to the instantaneous solar irradiation by adjusting the wastewater flow rate to the current intensity supplied by the PV array. The experiments were conducted in Kavala Institute of Technology (latitude 40° 55′, longitude 24° 22′, and altitude 138 m above the sea level). All operating parameters affecting the efficiency of the proposed process, such as wastewater conductivity, pH, flow rate, current density, electroprocessing time, and solar irradiance, were studied and optimal conditions were investigated. The experimental results showed that by applying a current density of 20 mA cm2, the chromium concentration in the treated electroplating wastewater was effectively reduced from its initial value of 96 mg L−1 to less than the permissible limit amounting to a removal percentage of over 99%. The corresponding electrical energy consumption was 8.4 kWh per m3 of treated wastewater. The proposed process is appropriate for removal of chromium from industrial effluents and especially for small applications in remote and isolated locations with lack of electric grid.

Treatment of Cr(VI) present in plating wastewater using a Cu/Fe galvanic reactor

In this study, we present the reduction of Cr(VI) present in chromium electroplating wastewater using batch and continuous systems with a galvanic Cu/Fe configuration. The chromium plating wastewater used in this work exhibited the presence of nitrate and sulfate ions, which are capable of competing with the reduction of chromium and copper in low quantities. As a result, the system was optimized by increasing the proton concentration to ensure a faster rate of 100% chromium reduction; thus, a shorter duration (less than 20min) was found when a pH value of 1.5 was used. In all of the systems, iron and copper release was registered; however, because lower than theoretical iron quantities were detected in the Cu/Fe system, additional copper cathode mechanisms are proposed for the reduction of Cr(VI). The monitoring of the ions present in the system showed that all nitrate, sulfate, and chloride ions were removed simultaneously (50.3%, 37.7%, and 91.8%, respectively), and copper was likely the major element responsible of for the removal of these ions. The continuous experiments also revealed that Cr(VI) reduction could be performed efficiently with a maximum reduction capacity of 189.6mg Cr(VI)/g iron, which is higher than that obtained in other recent electrochemical works. The SEM/EDS and XRD results definitively confirm that anodic and cathodic Cr(VI) reduction was taking place and that the formation of sludge occurred principally by precipitation of iron. The cogenerated energy and gas (H2 and N2) are valuable subproducts that enhance the sustainability of the process, and the system also has the following known advantages: no energy input into the reactor, lower sludge generation, cathode reuse and the possibility to discharge the treated wastewater to national waters or reuse it in the rinsing process.

Recovery of chromium from plastic plating wastewater by cetyltrimethylammonium bromide MEUF and electrodialysis

To study the recovery of chromium for micellar-enhanced ultrafiltration (MEUF) process, a two-stage process was designed to concentrate chromium by MEUF with cetyltrimethylammonium bromide (CTAB), then recovered by electrodialysis (ED). Wastewater from full-scale plant containing heavy metals, including chromium, copper, and nickel, with pH < 2 were tested to investigate the effects of pH, surfactant/metal (S/M) ratio, and operating pressures. The results showed the removal efficiencies of chromate were increased at lower pH and higher CTAB concentration. The micellar hydrodynamic diameters (Dhs) gradually increased with the concentration of CTAB as Cr(VI) of 1.0 mM, and ranged from 3.1 to 4.7 nm. The zeta potentials gradually increased with the concentration of CTAB, but reached plateau for concentration higher than critical micelle concentration. The experimental results indicated that the removal of Cr(VI) by MEUF exceeded 96% for operating parameters of pH 1.53, ΔP = 30 psi, and S/M = 2. For ED process, the effects of current densities and current efficiencies were evaluated as the concentration ratio of 95%, and the chromium was able to pass through anion exchange membrane to recover at the anode side of the ED process up to 85.3% at current density of 20 mA/cm2, and operating time of 360 min.

Comparison of pH Adjustment and Electrocoagulation Processes on Treatability of Metal Plating Wastewater

This study includes both the removal of heavy metals and chemical oxidation demand from metal plating wastewater with pH adjustment and electrocoagulation processes and a comparison of these two processes. For the pH adjustment, process experimental works were studied for five pH levels as 6.0, 7.0, 8.0, 9.0, and 10.0. Optimum removal rates obtained at pH 8.0. With these operating conditions, 90% COD removal, 99.9% Zn (II) removal, 92.5% Cu (II) removal, 78.6% Ni (II) removal, and 50.5% Cr (VI) removal efficiencies were gained. For the electrocoagulation process, the optimum working conditions were found using response surface methodology (RSM) with a 5-level, 6-replicate central composite design (CCD). The optimum working conditions of the electrocoagulation process for pH, reaction time, and current density were determined as 8.0, 90 min, and 250 A/m 2 , respectively. At this condition, 90% COD, 100% Zn, 97% Cu, 90% Ni, and 75% Cr removal efficiencies were obtained. Treatment costs for each process per unit cubic meter wastewater were calculated as $91 and $34.8.