Effluents metal plating

Concentrated waste solutions are obtained from spent metal plating baths and etchants. However, the majority of metal wastes are soflds or sludges obtained from the hydrolysis of metal-bearing solutions and industrial process effluents. Most of these water-insoluble wastes are composed of hydroxides or basic salts of the contained metals. Eor processing by hydrometallurgical routes the materials must be brought into solution usually by acid or ammoniacal or alkaline digestion. 

Liquid Solution Metal plating effluent spent acids wash-waters... 

Liquid Liquid Liquid-gas Liquid-liquid Liquid-solid Solution Foam Emulsions Slurry Suspension Metal plating effluent spent acids wash-waters Detergent foam Oil-in-water (e.g. suds) water-in-oil Aqueous effluent from fume scrubbing... 

Cyanide compounds are useful to society in terms of their key role in synthetic and industrial processes, for certain fumigation and agricultural uses, and for some therapeutic applications (Ballantyne and Marrs 1987). Cyanides are present in effluents from iron and steel processing plants, petroleum refineries, and metal-plating plants, and constitute a hazard to aquatic ecosystems in certain waste-receiving waters (Smith et al. 1979) and to livestock (USEPA 1980 Towill et al. 1978). Cyanide serves no useful purpose in the human body, yet it is present in our food, air, and water (Becker 1985). 

DSA-02 oxide-coated Ti anode (DSA = Dimensionally Stable Anode) is placed, thus creating a large cathode volume. The effluent solution flows perpendicularly through the electrodes with a typical flow rate of 0.5 dm3 s-1. The flowthrough metal electrodes have an active area approximately 15 times their geometric area. The cell allows air sparging to increase the mass-transfer. The current efficiency is about 40% when the inlet concentration of the metal ions is 150 to 1500 ppm and the concentration at the out-let is about 50 ppm. The cell is currently used for the treatment of recirculated wash-waters from acid copper, copper cyanide, zinc cyanide, zinc chloride, cadmium sulphate, cadmium cyanide and precious metal plating and washwaters from electroless copper deposition. Since the foam metal electrodes are relatively expensive the electrodes... 

Table 4.1 Bioassay results (toxic threshold values in TUs) before (B) and after (A) biodegradation of five effluent samples, each representing one of the following industrial sectors (1) organic chemical production (2) inorganic chemical production (3) pulp and paper (4) metal plating (5) textile (Costan et al., 1993, pp. 133-5). 

Metals and metal finishing Mining effluent treatment Plating rinse water Reuse and recovery of metals... 

Environment issued the Environmental Quality Standards for ground water pollution. Many hazardous species are required to be monitored and maintained to protect our health. Eor hazardous substances, ionic species are analyzed with 1C, which has also been used to monitor cyan in effluents from metal plating industries. 1C has been commonly used not only for monitoring pollution but also for environmental analysis. Eigure 10 shows an anion chromatogram of a sample from an... 

Redox electrodes are mainly used as sensors in processes involving redox couples. An important application is in the metal plating industries where cyanide has to be removed from the plant effluents. Cyanide is efiminated in alkaline solutions by oxidation with chlorine gas in the first step to cyanate ions and then continuing the oxidation process to produce nitrogen and carbon dioxide as the final products ... 

RDE Refining of Cyanide Industriai Wastewaters Cyanides are used in many industrial processes such as surface treatment and noble metal plating. After several cycles the baths must be renewed in order to maintain the same operating conditions. The conventional physicochemical process applied to eliminate cyanide from liquid effluents is mainly oxidation by hypochlorite or ozone. Depleted wastewaters contain O.lmg/L of free cyanide and may be rejected into the environment. The new environmental regulations are more restrictive and concern both free and total cyanide. RDE technology was applied in order to reduce both free and complexed cyanide levels. 

Industrial Wastewater Treatment. Industrial wastewaters require different treatments depending on their sources. Plating waste contains toxic metals that are precipitated and insolubiHzed with lime (see Electroplating). Iron and other heavy metals are also precipitated from waste-pidde Hquor, which requires acid neutralization. Akin to pickle Hquor is the concentrated sulfuric acid waste, high in iron, that accumulates in smokeless powder ordinance and chemical plants. Lime is also useful in clarifying wastes from textile dyeworks and paper pulp mills and a wide variety of other wastes. Effluents from active and abandoned coal mines also have a high sulfuric acid and iron oxide content because of the presence of pyrite in coal. 

Yourfacility is involved in chrome plating of metal parts, which produces an aqueous plating waste that is treated on-site to recover chromium sludge. The effluent from the on-site treatment plant, which contains chromium compounds (a listed toxic chemical), is piped to a POTW. The chromium sludge is transferred to an off-site, private ly owned firm tor the recovery of the chromium. 

Concentrated metal hydroxide sludge is pumped from the clarifier to a polypropylene plate filter press [T-102], The plate filter press56 is of sufficient capacity without any buildup in the lamellar portion of the unit. This also prevents any overflow of precipitate to the sewer system. The metal hydroxides form a dense sludge cake suitable for disposal in an approved landfill. The liquid effluent from the plate filter is returned to the surge tank [T-99],... 

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