Wastewater zinc processing

Crane, R.S., Barton, P., Cartmell, E., Coulon, E, Hillis, P, Judd, S.J., Santos, A., Stephenson, T. Lester, J.N. (2010) Fate and behaviour of copper and zinc in secondary biological wastewater treatment processes. 1. Evaluation of biomass adsorption capacity. Environmental Technology, 31, 705-723. 

We have also developed an SUM system with strip dispersion effective at the low feed pH of also about 2 for zinc removal and recovery from wastewaters and process streams (Ho, 2001b, 2(X)2a, 2(X)3 Ho et al., 2001, 2002). The organic membrane solution in the strip dispersion consisted of 8wt% di(2,4,4-trimethylpentyl) dithiophosphinic acid (Cyanex 301), 2 wt% dodecanol, and 90 wt% Isopar L. The aqueous strip solution was 3 M sulfuric acid. 

About 100 gal of process wastewater is typically generated from 1 t of coke produced.15 These wastewaters from byproduct coke making contain high levels of oil and grease, ammonia nitrogen, sulfides, cyanides, thiocyanates, phenols, benzenes, toluene, xylene, other aromatic volatile components, and polynuclear aromatic compounds. They may also contain toxic metals such as antimony, arsenic, selenium, and zinc. Water-to-air transfer of pollutants may take place due to the escape of volatile pollutants from open equalization and storage tanks and other wastewater treatment systems in the plant. 

At some plants the blast furnace dust is recycled as feedstock to the sinter plant. At plants without sintering operations, blast furnace dust is sometimes mixed with other byproduct residues, briquetted, and recycled back to the blast furnace. In other plants, the dust is landfilled or stockpiled.1 Several techniques are available for removing the zinc and lead. The majority of blast furnace sludge is land disposed as solid waste or stockpiled. Because of the similarity between wastewater sludges generated by sinter plants and blast furnaces, these streams are commingled and cotreated.1 The blast furnace slag is cooled and processed to be reused for various applications such as onsite in-land reclamation and landfill construction. 

Electrolytic copper refining Blister copper Process wastewater Slimes containing impurities such as gold, silver, antimony, arsenic, bismuth, iron, lead, nickel, selenium, sulfur, and zinc... 

Many toxic pollutants were detected in the process wastewaters from metal molding and casting processes. The toxic pollutants detected most frequently in concentrations at or above 0.1 mg/L were phenolic compounds and heavy metals. The pollutants include 2,4,6-trichlorophenol, 2,4-dimethyl-phenol, phenol, 2-ethylhexyl, cadmium, chromium, copper, lead, nickel, and zinc. Each type of operation in the foundry industry can produce different types of pollutants in the wastewater stream. Also, because each subcategory operation often involves different processes, pollutant concentrations per casting metals may vary. 

Prominent among the heavy metals found in the wastewater generated in the copper sulfate industry are copper, arsenic, cadmium, nickel, antimony, lead, chromium, and zinc (Table 22.11). They are traced to the copper and acids sources used as raw materials. These pollutants are generally removed by precipitation, clarification, gravity separation, centrifugation, and filtration. Alkaline precipitation at pH values between 7 and 10 can eradicate copper, nickel, cadmium, and zinc in the wastewater, while the quantity of arsenic can be reduced through the same process at a higher pH value. 

Hexavalent chromium and metals such as zinc and nickel that are present as impurities in the chromites ore are predominant pollutants associated with the sodium dichromate plant. They are generally removed through alkaline precipitation, clarification, filtration, and settling processes. The wastewater is treated with sodium sulfide to reduce hexavalent chromium to trivalent chromium,... 

As was indicated in the previous section, the concentration of iron in the mixed wastewaters ranged from 5980 to 6100 mg/L its pH was 0.7 and zinc concentration was 15 pg/L. Since these wastewaters come only from acid baths and not from other processes of the plant, parameters such as cadmium and fluoride are not encountered. The discharge standards for the metal industry effluents set by the Turkish Water Pollution Control Regulation (Official Gazette, Table 15.7, September 4, 1988) are shown in Table 28.10.1... 

Note Most process operations are accomplished without the use of process water No wastewater characterization data available Anode production (zinc, mercury, TSS, oil, and grease) Cathode production (copper, chromium, zinc, lead, silver, nickel, mercury, and TSS)... 

Chemical precipitation. Chemical precipitation followed by solids separation is particularly useful for separating heavy metals. The heavy metals of particular concern in the treatment of wastewaters include cadmium, chromium, copper, lead, mercury, nickel and zinc. This is a particular problem in the manufacture of dyes and textiles and in metal processes such as pickling, galvanizing and plating. 

In the fatty acid distillation process, wastewater is generated as a result of an acidification process, which breaks the emulsion. This wastewater is neutralized and sent to the sewer. It will contain salt from the neutralization, zinc and alkaline earth metal salts from the fat splitting catalyst, and emulsified fatty acids and fatty acid polymers. 

In the pesticide industry, metals are used principally as catalysts or as raw materials that are incorporated into the active ingredients, for example, metallo-organic pesticides. Priority pollutant metals commonly incorporated into metallo-organic pesticides include arsenic, cadmium, copper, and mercury. For metals not incorporated into the active ingredients, copper is found or suspected in wastewaters from at least eight pesticides, where it is used as a raw material or catalyst zinc becomes part of the technical grade pesticide in seven processes and mercury is used as a catalyst in one pesticide process. Nonpriority pollutant metals such as manganese and tin are also used in pesticide processes. 

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