Electroplating Waste Water Research Articles

Development of a process for biodetoxification of metal cyanides from waste waters

A bacterial consortium capable of utilising metal cyanides as a source of nitrogen was used to develop a microbiological process for the detoxification of metal cyanides (viz. copper cyanide and zinc cyanide) from electroplating waste water. Optimal conditions biodegradation of both the metal-cyanide compounds were pH 7.5, temperature 35°C, inoculum size 10 9 cells per ml and glucose or sugarcane molasses requirement of 5 mM or 0.6 ml/l, respectively. Metal precipitates obtained during metal-cyanide biodegradation were identified as metal-hydroxides. When the treatment was carried out in a 27 l rotating biological contactor (RBC) in continuous mode, the system could achieve >99.9% removal of 0.5 mM metal cyanide (ca. 52 mg/l cyanide and 30–40 mg/l copper/zinc) in 15 h with sugarcane molasses as carbon source. The RBC treated effluent was found to be safe for discharge in the environment as confirmed by chemical analysis and fish bioassay studies.

Solvent Extraction of Chromium from Dilute Aqueous Solution

ABSTRACT Electroplating process of chromium generates inevitably hexavalent chromium species that is strictly regulated by the environmental protection acts. In general, chemical precipitation method is widely employed for treating the waste water containing hexavalent chromium. This study investigates solvent extraction of Chromate with anion exchange extractants like Alamine 336 and Aliquat 336 for application to treatment of electroplating waste water with low concentration of hexavalent chromium. The result showed that Aliquat 336 of quaternary amine effectively extracted hexavalent chromium and was superior to Alumine 336.

Expert membrane system design and selection for metal finishing waste water treatment

An integrated decision support system to aid in the design and selection of membrane-based treatment systems for metal finishing and electroplating waste water is the focus of this research. The modular system offers basic information on membrane, electroplating and metal finishing processes, an expert system for treating waste water from these processes, a simulator and a multicriteria scoring module for ranking the design options. The simulator tracks ion concentrations, offers design recommendations based on effluent limits of regulated materials and technical feasibility, and calculates recovery and crude cost estimates of the treatment system. Although the system targets metal finishing and electroplating, it addresses the more fundamental issue of membrane technology transfer.

Heavy metal uptake during anaerobic digestion of combined electroplating and brewery wastewaters

Batch and continuous culture laboratory-scale experiments were conducted to quantify the effect of combining chrome and nickel electroplating effluent (EE) and brewery effluent as substrate for established anaerobic digester granules. EE at a 1:12 ratio in brewery effluent was inhibitory to anaerobic digestion but acclimation at a 1:24 ratio occurred during continuous culture experiments. At least 90% of the chromium and nickel was absorbed by the granules with nickel attaching to granule perimeters while chromium penetrated into deeper recesses. © Rapid Science Ltd. 1998

Treatment of Chromium Electroplating Wastewater by an Automated Solvent Extraction Technique

The results of a comprehensive and coherent study for a better understanding of the extraction of Cr(VI) by Aliquat 336 in hydroxide form are presented. Distribution data were obtained under conditions typical of waste rinsewater generated in chromium electroplating. A solvent extraction process was developed to recover and concentrate chromium from the rinsewater. The feasibility of the process to remove chromium to a level meeting very stringent environmental requirements was demonstrated with automated mixer-settler solvent extraction units.

Pilot scale membrane separation of electroplating waste water by reverse osmosis

Electroplating waste water containing copper was treated by means of reverse osmosis (RO) membrane separation on a pilot scale. The copper concentration in the untreated waste water was 340 ppm. After the treatment, the concentration in the treated water was below 4 ppm which is the Hong Kong government discharge limit. It is shown that, by increasing transmembrane pressure drop, metal concentrations in the treated water can be further reduced. This study suggests that larger scale operations on treating electroplating waste water by RO membrane separation is possible and effective. Effects of operating variables including transmembrane pressure drop and temperature on membrane separation performance were studied and explained based on the solution-diffusion model. The present study is part of the recent investigation of industrial waste water management sponsored by the Hong Kong Government. The purpose of this project is to provide guidelines to the local industries for waste minimization which is closely monitored by the Hong Kong legislature.

Determination of metal ions as EDTA complexes by reversed-phase ion-pair liquid chromatography

A reversed-phase ion-pair liquid chromatographic method was developed for the determination of metal ions in aqueous solution. Metal ions were first chelated with EDTA, followed by injection into the chromatographic system. A reversed-phase C 8 column was used to separate the chelate ions with an eluent consisting of acetonitrile-water mixture (8 + 92, v/v) containing 0.002 M tetrabutylammonium as the counter ion. UV detection at 242 nm was applied. Factors affecting the ion-pair formation and the chromatographic separation were studied. This method can be applied to the determination of metal ions such as Pb, Ni, Cd, Fe and Cu. The linear dynamic range is larger than two orders of magnitude, the detection limit is at the ng ml -1 level and the R.S.D. is ca. 3% at mid-calibration range. The method has been successfully used in metal analysis of electroplating waste water. The results are comparable to those of atomic absorption spectrometry.

Separation of multicomponent solutions using reagent ultrafiltration

Efficiency of ultrafiltration separation may be greatly increased when preliminary selective binding components of a solution to the form of aggregates (high molecular substances and colloidal particles). One of the possible ways of aggregation is the formation of complexes with water soluble polymers. One can find such a polymer agent which binds only one component. Hence only this component will be rejected during ultrafiltration. The second way is the conversion of a component to the form of hydroxide. This method is acceptable for removal of heavy metal ions. In this case we cannot receive very high selectivity as in the first, but it is possible to get a rejection effect using only pH adjustment. In this work we used reagent ultrafiltration for purification of electroplating waste waters from heavy metal and for selective concentration of scandium from brackish waters.

Liquid chromatographic behaviour of chelates of vanadium(V), copper(II), cobalt(III) and chromium(III) with 2-(3,5-dibromo-2-pyridylazo)diethylaminophenol

The reversed-phase liquid chromatographic behaviour of the chelates of VV, CuII, CoIII and CrIII with 2-(3,5-dibromo-2-pyridylazo)diethylaminophenol(3,5-diBr-PADAP) was studied using a C18 column, and a method for the simultaneous determination of VV, CuII, CoIII and CrIII was developed. A mobile phase of methanol-acetonitrile-water (84 + 12 + 4) containing 0.11 mmol dm–3 cetyltrimethylammonium bromide and 0.1 mmol dm–3 NaOAc–HCOOH(pH 3.5) was found to be the best. The chelates were detected at 590 nm. The calibration graphs were linear for 0.20–6.40 µg ml–1 of VV, 0.40–12.80 µg ml–1 of CuII, 0.08–2.56 µg ml–1 of CoIII and 0.40–6.40 µg ml–1 of CrIII. The detection limits were 0.2, 0.4, 0.04 and 0.2 ng for VV, CuII, CoIII and CrIII, respectively. The method was applied to the determination of VV, CuII, CoIII and CrIII in electroplating waste water samples.

Electrolytic oxidation of cuprocyanide electroplating waste waters under different pH conditions

The main purpose of this work was to investigate the electrolytic oxidation of cuprocyanide solution with various total cyanide to copper molar ratios ranging from 2.8 to 20 and under different pH conditions. In strong alkaline solution (pH≥12), cuprocyanide ions Cu(CN) /(−1)− , wheren=2, 3 or 4, are directly electroxidized, and copper oxide precipitates on the anode. Cyanate ions, as well as nitrogen gas, were detected as the products and 0.30–0.43 g mol of total cyanide was destroyed per Faraday. For less alkaline solutions (pH<12), cuprocyanide ions first dissociated to free cyanide ions and then electroxidized. At a pH of 10.5–11.7, cyanate ion and brown azulmin polymer were produced in the anolyte. In the neutral solution (pH=7.0–8.6), carbonate and ammonium ions and azulmin were formed and 0.52–0.56 g mol of total cyanide was destroyed per Faraday. In weak acidic solution (pH=5.2–6.8), oxalate and ammonium ions and white oxamide were produced and 1.01–1.18 g mol of total cyanide were destroyed per Faraday.

Determination of cobalt, copper, mercury, and nickel as bis(2-hydroxyethyl)dithiocarbamate complexes by high-performance liquid chromatography

Ammonium bis(2-hydroxyethyl)dithiocarbamate (HEDC) is used as a precolumn derivatizing reagent for the reversed-phase HPLC determination of Co(II), Cu(II), Hg(II), and Ni(II). The metal-HEDC complexes are soluble in water, which eliminates the need to extract them into an organic solvent prior to analysis. Co(II), Cu(II), and Ni(II) can be determined by direct aqueous injection onto a C18 column in the range of 0.005-10.0 mg/L, with a precision of 1.5-3.2%. Detection is at 405 nm. The Hg(II)-HEDC complex is preconcentrated on an on-line adsorption column prior to HPLC analysis. After preconcentration, Hg(II) can be determined in the range of 0.02-25..mu..g/L with a precision of less than 2%. The analysis of spiked electroplating waste waters showed good agreement with expected values.

シアン化亜鉛めっき排水中の鉄シアノ錯体の沈殿除去

(1) [Fe(CN)6]3- in aqueous solution was efficiently removed as Zn2Fe(CN)6 by reducing it with a mixed reducing agent of sulfite and thiosulfate ions (1:1) in the presence of Zn2+. In this process, moreover, trace amounts of Cu2+ were found to accelerate the reduction of [Fe(CN)6]3- markedly owing to a synergistic action with Zn2+.(2) The above process was applied to the removal of the remaining [Fe(CN)6]3- after alkaline chlorination of waste water from cyanide zinc electroplating solutions. As a result, total cyanide concentration was reduced to a level of less than 0.1ppm except when Ni was present, and it was possible to automate the whole operation from alkaline chlorination to the remeval of [Fe(CN)6]3-.(3) The volume of cyanide-bearing sludge produced by the treatment of electroplating waste water containing cyanides can be greatly decreased by the above process involving the reduction of [Fe(CN)6]3- in the vicinity of pH6, followed by separation of the precipitate formed.(4) In processing electroplating waste water containing Ni, the primary alkaline chlorination treatment should be carried out by a batch process to make sure that the destruction of [Ni(CN)4]2- is complete.

Chromosomal aberrations induced by electroplating waste water.

It is established that heavy metal complex ions and cyanides induce chromosomal aberrations in Allium cepa. It is concluded that these pollutants present in the electroplating waste water increase mutation rates when they are present in high concentration. Further studies on the role of individual metal ions and cyanides may throw more light on their capacity in bringing about chromosomal aberrations.

Mass Transport Characterization of Donnan Dialysis: The Nickel Sulfate System

There is a need for reliable models of the mass transfer characteristics of hollow tube Donnan dialyzers, to guide application to industrially significant problems such as recovery from electroplating waste water. This work is focused on determining mass transport correlations in a shell‐and‐tube dialyzer, fabricated from ion‐selective membranes, used to extract nickel from dilute nickel sulfate solution with sulfuric acid as the stripping agent. Correlations between mass transport coefficient and Reynolds number are reported for both laminar and turbulent flow regimes.