Plating Wastewater Research Articles

Selective recovery of silver ions from aqueous solutions using modified silica beads with Adogen 364

AbstractIn this work, a method to prepare new adsorbents for the recovery of silver ions was studied. Cheap silica beads for industrial use were obtained and silanized with dichlorodimethylsilane after pretreatment with hot water to increase the silanol contents, followed by immobilization of Adogen 364 (a mixture of trialkyl tertiary amines, Witco Co), a commercial solvent extractant that has a good affinity with silver ions. This sample, designated as K2WDA, was proven to be effective for the adsorption of silver ions from aqueous solutions with fast adsorption rates where sodium nitrate was added as a complexation agent to increase the adsorption capacity of the basic extractant. The adsorption capacity of K2WDA at pH 5 was 0.125 mmol g−1 and corresponded to the proposed mechanism that silver ions adsorb on the functional group with a 1:1 molecular ratio. Selectivity for silver ions in synthetic plating wastewater containing Cu2+ and Ni2+ ions was excellent due to thermodynamic stability. In addition, 80% of the silver ions adsorbed could be recovered with sodium thiosulfate solution rather than acids and the solution was concentrated more than 10 times compared with the original solution. For practical application, a semi‐batch reactor was considered and numerical modeling was performed.© 2002 Society of Chemical Industry

Perturbations of population growth in a microcosm by industrial metal plating and ice cream mills wastewater and landfill leachate.

Perturbations of population growth in a microcosm by industrial metal plating and ice cream mills wastewater and landfill leachate.

Co-removal of hexavalent chromium during copper precipitation

In our recent study using the nucleated precipitation technology to treat plating wastewater, it was found that about one half of hexavalent chromium was co-removed with copper, nickel and zinc. Since hexavalent chromium could not react with either hydroxide or carbonate to from precipitates, this study was undertaken to evaluate the mechanism(s) involved in the chromium co-removal. Batch tests were conducted with synthetic solutions containing either only copper or both copper and hexavalent chromium. Metal precipitation was induced by adding Na2CO3 to different pH, and the quantitative removal of copper and chromium was determined. Besides, the [Cr]/[Cu] molar ratio of produced precipitates were also assessed in conjunction with the EDAX analysis to determine their compositions. Experimental results indicate that for pure copper solution, precipitation begins at pH 6.0, and completes at pH 7.0. The chemical forms of the precipitates are copper carbonates [CuCO3 x Cu(OH)2 and CuCO3 x 2Cu(OH)2]. On the other hand, in a bi-metal solution of copper plus chromium, precipitation of copper begins at about pH 5.0, and copper precipitation is always accompanied by some chromium removal. From the removal stoichiometry of the two metals, it is found that at low pH, the co-removal is a result of "co-precipitation" which results in the formation of CuCrO4 crystallites. Once such crystallites are formed, they provide a heterogeneous environment which enhances an early formation of copper carbonate at a lower pH (below 5.5). It is further found that once copper carbonate precipitates are produced, the remaining soluble will precipitate in such form, and at this stage further removal of copper is no longer accompanied by additional chromium removal. The test data also reflect that the produced copper carbonates are positively charged, as verified by zeta potential measurement, at pH below 7.5. Thus they are able to adsorb some anionic chromium (existing as chromate) through electrostatic attraction and/or inorganic ligand exchange. At pH of 6 to 10, the extent of adsorption decreases with increasing pH, and the adsorption capacity seems to coincide with the progressive reduction of positive zeta potentials of the precipitated particles.

Preparation of water soluble chitosan blendmers and their application to removal of heavy metal ions from wastewater

High purity water soluble chitosans (WsCs) were employed as a flocculant to remove heavy metal ions from wastewater of industrial plating wastewater treatment complex. Their weight average molecular weights and polydispersities were 272,000∼620,000 g/mol and 1.4∼1.9 range, respectively and were readily soluble in water in the pH range of 3∼11. Heavy metal ions such as chromium, iron and copper were removed well by WsCs. When WsCs was blended with either sodium N,N-diethyldithiocarbamate trihydrate (SDDCT) or sodium salicylate (SSC), the removal efficiency was further increased primarily due to the excess amount of hydrophilic sulfonic and carboxylic groups. Especially, in the case of WsCs-SSC the remaining chromium and copper concentrations were 0.1 mg/L and 9.5 mg/L, which are 1/15 and 1/3 compared with that of pure WsCs, respectively. The former is within the acceptable limit, but the latter is not. Therefore, the effective copper flocculant remains to be studied.

無電解ニッケルめっき老化液処理への還元晶析法の適用 反応挙動に対する種晶比表面積の影響

In this study, Ni2+ removal from electroless nickel plating wastewater (A. co., Ltd.) by reduction crystallization was investigated, to make clear the effect of seeds specific surface area on the Ni2+ removal characteristics. Although the main reaction in this research is the same as the one in electroless nickel plating, the authors have proposed reduction crystallization in which wastewater from electroless nickel plating contacts with suspended nickel powder, to remove and recover Ni2+. The results could be obtained on the relationship between the pH change profile and recovery efficiency in the reaction process, in which nickel powders having various specific surface area were used as seeds. Experimental results were discussed, considering surface conditions of grown nickel and the behavior of produced fines. With a constant 10% NaOH solution feed rate, the pH profile changed in the process of Ni2+ reduction, by changing the specific surface area of seeds, which means that Ni2+ removal efficiency was affected by the specific surface area of seeds. When constant pH7 was maintained, higher removal efficiency (0.99; Ni2+ concentration in the treated water 2.5×10-2g·dm-3) could be obtained, although the specific surface area of Ni seed powder varied. Specific surface of seeds, based on the roughness of seed crystal, was suggested to be an effective factor on the Ni metal coating behavior on the seed surface and also the phenomena of fines production in the process of Ni deposition.

Removal of heavy metals in plating wastewater using carboxylated alginic acid

Potentially, biosorption is an economic process for metal sequestering from water. Carboxylated alginic acid showed high uptake capacities for heavy metals of 5-6 meq/g dry mass. For application to actual plating waste-water, the carboxylated alginic acid was immobilized using PVA. In order to remove chelating or organic materials in plating wastewater, oxidation using sodium hypochlorite was performed as a pretreatment. When carboxylated alginic acid bead was applied in a packed-bed contactor, the breakthrough point of copper ion in the acid-alkaline wastewater appeared around 350 bed volumes; the breakthrough point of nickel ion in the chelating wastewater emerged around 200 bed volumes. The adsorption capacity for heavy metal of the carboxylated alginic acid bead was higher than that of a commercial ion exchanger (IR-120 plus) in plating wastewater.

Implications of chemical-based effluent regulations in assessing DNA damage in fathead minnows (Pimephales promelas) when exposed to metal plating wastewater.

The application of chemical-based regulation on effluents has limitations because of their diverse chemical components, complicated interactions between contaminants, and the lack of information on the bioavailability of constituents (U.S.EPA 1991). In Korea, like in most developing countries, environmental regulations for the protection of the aquatic biota from discharges are based only on this chemical-based approach. The Permissible Wastewater Discharge Standards (PWDS) are the current legislation in Korea. The discharge limits are set for several heavy metals (e.g. Cr, Fe, Zn, Cu, Cd, Hg, As, Pb, etc.), a few organics (phenol, PCB, trichloroethylene, tetrachloroethylene, etc.) and some physicochemical parameters (pH, temperature, etc.). Among these pollutants, the trace metals are important because they might adversely affect the indigenous aquatic biota even at low levels. Genetic toxicity of trace metal has been a major concern (Barron and Adelman 1984; Ciccarelli and Wetterhahn 1985; Parrott and Sprague 1993; Beyersmann and Hartwig 1994; Hartwig et al. 1994). Metals readily bind to phosphate groups and to heterocyclic bases of the DNA and, hence not only change the stability, but also hinder the normal functioning of the DNA (Eichhom et al. 1970). The resulting consequences of metal-induced DNA damage include mutagenesis, carcinogenesis, and/or teratogenesis (Jones and Parry 1992).

Application of a fish DNA damage assay as a biological toxicity screening tool for metal plating wastewater

AbstractThe utility of a fish DNA damage assay as a rapid monitoring tool was investigated. Metal plating wastewater was chosen as a sample because it contains various genotoxic metal species. Fish DNA damage assay results were compared to data generated from the conventional whole effluent toxicity (WET) test procedure. The Microtox® assay (Azur Environmental, Carlsbad, CA, USA) using Vibrio fischeri was also employed. Eleven samples from two metal plating companies were collected for this evaluation. For the fish DNA damage assay, 7‐d‐old fathead minnow larvae, Pimephalespromelas, were utilized. They were exposed to a series of dilutions at 20°C for 2 h. Whole effluent toxicity tests conducted in this study included two acute toxicity tests with Daphnia magna and fathead minnows and two chronic toxicity tests with Ceriodaphnia dubia and fathead minnows. The fish DNA damage assay showed good correlations with both the acute and chronic WET test results, especially with those obtained with fathead minnows. The kappa values, an index of agreement, between the fish DNA damage assay and WET tests were shown to be acceptable (kappa ≥ 0.55). These findings imply that this novel fish DNA damage assay has use as an expedient toxicity screening procedure since it produces comparable results to those of the acute and chronic fathead minnow toxicity tests.

Removal of Heavy Metals from Plating Wastewater by Crystallization/Precipitation of Gypsum

AbstractA high surface area was created during nucleation and crystal growth of gypsum by mixing calcium and sulfate ions, causing adsorption of heavy metals on the colloids of gypsum and capsulation in the subsequent precipitation process. In addition to the effect of surface area, zeta potential and surface pH of the gypsum colloids, ionic strength of solution, as well as solubility and particle size of the metal hydroxide influenced the extent of uptake of heavy metals from wastewater.

Heavy meatals removal by a promising locally available aquatic plant, Najas graminea Del., in Taiwan

This study uses an aquatic plant, Najas graminea Del., to treat man-made wastewater containing single and/or binary components of copper, lead, cadmium and nickel. Adsorption experiments demonstrate that the adsorption process correspond to the Lagergren kinetic model with the rate constant close to 0.01 min−1; meanwhile, the equilibrium results corresponds to the Langmuir adsorption isotherm. Notably, the rate constants of metals are not significantly different between each other. Competitive effect on the adsorption kinetics of cadmium is insignificant with the background solute (lead) concentration up to 10 mg/l; while significant deviation observed with concentration of lead reached 100 mg/l. In addition, the maximum adsorption density of cadmium is reduced by around 50% in the presence of 100 mg/l of lead. A simulated copper plating wastewater is also treated by Najas graminea Del. to demonstrate its efficiency in removing metals from wastewater with multi-cations/anions.

溶媒抽出法による無電解コバルトめっき廃液処理

The application of solvent extraction to the treatment of electroless cobalt plating wastewater has been investigated. In the treatment of caustic and ammoniacal alkaline plating wastewaters, TOMAC is favorable to the extraction of cobalt and citrate ion, and the separation from hypophosphite ion and phosphite ion. The extraction of hypophosphite ion from alkaline solutions with TOMAC is suppressed by loading the organic phase with phosphite ion, and the separation efficiency of phosphite ion and hypophosphite ion in the alkaline region is improved using the mixed extractants of TOMAC and phosphine oxides such as CYANEX 923.

Heavy meatals removal by a promising locally available aquatic plant, Najas graminea Del., in Taiwan

This study uses an aquatic plant, Najas graminea Del., to treat man-made wastewater containing single and/or binary components of copper, lead, cadmium and nickel. Adsorption experiments demonstrate that the adsorption process correspond to the Lagergren kinetic model with the rate constant close to 0.01 min−1; meanwhile, the equilibrium results corresponds to the Langmuir adsorption isotherm. Notably, the rate constants of metals are not significantly different between each other. Competitive effect on the adsorption kinetics of cadmium is insignificant with the background solute (lead) concentration up to 10 mg/1; while significant deviation observed with concentration of lead reached 100 mg/1. In addition, the maximum adsorption density of cadmium is reduced by around 50% in the presence of 100 mg/1 of lead. A simulated copper plating wastewater is also treated by Najas graminea Del. to demonstrate its efficiency in removing metals from wastewater with multi-cations/anions.

Inhibition of Nickel Precipitation by Gluconate. II: Kinetic Modeling

Gluconate has been shown to inhibit nickel precipitation. This can result in adverse system performance when treating nickel plating wastewater. A kinetic model based on the formation of major species was developed to simulate nickel precipitation in the absence and presence of gluconate. The model was calibrated and verified against batch kinetic experimental results. The model simulated the studied nickel-gluconate systems well. However, no universal mechanisms could be adopted to explain all of the phenomena observed in the kinetic study, indicating different controlling mechanisms in each system. The results of this study can be used to evaluate optimum conditions for nickel precipitation and to aid in the design of treatment processes enhancing the optimization of nickel recovery from metal finishing wastewaters.

無電解ニッケルめっき廃液処理への溶媒抽出法の適用

Electroless plating is widely used in electronics, semiconductor and automobile industries as a surface treatment technique, because uniform thickness metal can be deposited on plastics, ceramics or polymers with intricately shaped surfaces. Above all, electroless nickel plating using hypophosphite as a reducing agent is very popular and has been studied a lot, since it gives excellent plated metal surfaces with corrosion resistance, lubricity and magnetic properties. As metal deposition progresses in this process, however, phosphorous acid increases in the plating bath, which causes degradation of the bath solution. Therefore, the bath itself must be disposed after a certain number of turnovers before the degradation occurs. The waste solution from electroless nickel plating bath contains a large quantity of nickel, hypophosphite, phosphite and organic compounds such as citrate, malate or succinate. It is quite harmful to the environment and at the same time, these hazardous wastes can be viewed as resources if properly handled. Therefore, it is very important to develop an effective extraction technique removing these chemical substances separately.In the present study, the application of solvent extraction to the treatment of electroless nickel plating waste water was investigated. In the treatment of caustic alkaline plating waste water, TOMAC is favorable to the extraction of nickel and citrate, and the separation from hypophosphite and phosphite. It is difficult to apply TOMAC to the treatment of ammoniacal alkaline plating waste water, while the use of chelating extractants such as LIX 26 is favorable to extraction of nickel. Meanwhile, the application of solvent extraction to the treatment of acidic plating waste water is difficult.

表面処理と環境‐水質編 錯体を含むめっき液のフェントン法による廃液処理

表面処理と環境‐水質編 錯体を含むめっき液のフェントン法による廃液処理

表面処理と環境‐水質編 めっき廃水の処理

表面処理と環境‐水質編 めっき廃水の処理

表面処理と環境‐水質編 高効率凝集分離装置によるめっき排水処理

表面処理と環境‐水質編 高効率凝集分離装置によるめっき排水処理

Agricultural By-products as Metal Adsorbents: Sorption Properties and Resistance to Mechanical Abrasion

Defatted rice bran, soybean and cottonseed hulls were evaluated for their sorption properties and resistance to mechanical abrasion in consideration of their potential use as commercial metal adsorbents. These by-products were evaluated using both laboratory prepared solutions and metal plating wastewater for their ability to adsorb Zn(II) and/or Cu(II) and Ni(II). Extrusion stabilized, pilot plant-prepared brans had greater adsorption capacities and adsorption efficiencies than expander stabilized, commercially available bran. All rice brans possessed low mechanical abrasion resistance in batch applications. NaOH- and HCl-washed soybean and cottonseed hulls had generally higher adsorption efficiencies than water-washed (control) hulls, but had higher or lower adsorption capacities, respectively, than water-washed hulls. Heat-treated cottonseed and soybean hulls had lower adsorption properties than water-washed hulls. Unlike rice bran, both soybean and cottonseed hulls were found to have high mechanical abrasion resistance in batch applications. Reuse of hulls after one adsorption/desorption (sorption) cycle resulted in a large decrease in adsorption capacity which classified hulls as single-use adsorbents when desorbed with HCl.

5401374 Electrolyzer for plating waste water: Leutwyler Rene Maegenwil, Switzerland Assigned to JWI Inc

5401374 Electrolyzer for plating waste water: Leutwyler Rene Maegenwil, Switzerland Assigned to JWI Inc

Effect of surfactants on recovery of nickel from nickel plating wastewater by electrowinning

The effect of surfactants on the electrowinning efficiency of the recovery of nickel from nickel plating wastewater was studied. Owing to the decrease of the effective electrode area and mass transfer coefficient of solution, the electrowinning efficiency was decreased by the presence of surfactants in wastewater. The higher the surface activity and the longer chain-length of the surfactant, the lower the electrowinning efficiency. This drawback could be eliminated by the addition of boric acid and with a greater rate of flow of solution. An attempt had been made to delineate the effect of boric acid on electrowinning efficiency.