Metal plating waste

UF can remove metal values from metal plating wastes provided the metals are first precipitated to form a colloidal suspension. The process is described in Chapter 2 in the section on cross-flow applications. Even though MF membranes provide a higher flux, they are more prone to flux decay than UF due to internal pore fouling. The long term UF flux may be higher than that from MF. 

Figure 8. Some emissions to the environment form the disposal of Aqueous acid metal-plating waste...

A third major class of physical separation is molecular separation, which is often based on membrane processes in which dissolved contaminants or solvents pass through a size-selective membrane under pressure. The products are a relatively pure solvent phase (usually water) and a concentrate rich in the solute impurities. Membrane processes including the special case of reverse osmosis to remove salts from water are discussed for the treatment of water in Chapter 5, Section 5.10. Electrodialysis, employing membranes alternately permeable to cations and to anions and driven by the passage of an electrical current (see Chapter 5, Section 5.10), is sometimes used to concentrate metal plating wastes and to reclaim dissolved metals. 

The metal plating waste products from a zinc plating process were added to portland cement and the hydration was followed by conduction calorimetry. At an addition level of 3-10%, the rate of hydration was greatly reduced,... 

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. 

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. 

Treatment of Industrial Wastes. The alkaline nature and inexpensive price of lime make it ideal for treatment of acid waste Hquors (6), including waste pickle Hquids from steel plants, wastes from metal plating operations, eg, chrome and copper plating, acid wastes from chemical and explosives plants, and acid mine wastewaters. 

The most common toxic metals in industrial use are cadmium, chromium, lead, silver, and mercury less commonly used are arsenic, selenium (both metalloids), and barium. Cadmium, a metal commonly used in alloys and myriads of other industrial uses, is fairly mobile in the environment and is responsible for many maladies including renal failure and a degenerative bone disease called "ITA ITA" disease. Chromium, most often found in plating wastes, is also environmentally mobile and is most toxic in the Cr valence state. Lead has been historically used as a component of an antiknock compound in gasoline and, along with chromium (as lead chromate), in paint and pigments. 

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. 

C04-0026. Cadmium ions are environmental pollutants found in mining waste, metal plating, water pipes, and industrial discharge. Cadmium ions replace zinc ions in biochemistry and cause kidney damage, high blood pressure, and brittle bones. Dissolved Cd " " impurities can be removed from a water sample... 

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). 

There is no wasted material during fabrication due to the available width of metal plate. 

In a centrally located recovery plant for the treatment of oxidic and hydroxidic metal containing waste (dust and sludge) from steel and metal works, including the plating industry, the main problem is the dominating amounts of iron. To avoid a secondary waste problem, special precautions have to be considered to create an iron product. One possibility is a pyro-metallurgical treatment to produce pig iron or a master alloy. 

The vendor claims that Ensol is applicable for the treatment of wastewaters including sewage after primary treatment, metal plating and finishing waters, and paper mill white water. The claim also extends to the treatment of solid wastes and soils, provided that they contain sufficient free water. 

Additional reductions in the amount of hazardous filter cake sludge produced were achieved with three process chemistry substitutions completed in September 1988, which eliminated a major source of chrome-containing wastes in the metal plating production facility. The initial substitutions replaced a chromic acid / nitric... 

The latest projects to eliminate the production of waste treatment sludges were undertaken in the wet process metal plating production area. The projects, completed in March 1989, involved the installation of separate cadmium, chrome, copper and nickel recovery systems. All of the recovery systems utilized redundant conventional ion exchange columns for initial metal waste recovery and concentration. 

Figure Thirteen (13) illustrates the specific components of the entire system. Because the manufacturing process involves heavy metals plating, the contaminated rinse water contains some hazardous materials, thereby requiring special waste treatment considerations.

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