Heavy metals removal from waste waters

Sulffde Precipitants. The removal of heavy metals from waste waters using soluble sulfides has been studied extensively. Peters and Ku (13) showed that pH strongly affects the removal of heavy metal sulfides from waste water. Their data showed that the solubilities of most heavy metal sulfides, other than arsenic (HI) sulfide, decreases up to about pH 9. Since most phosphate fluid fertilizers, such as 10-34-0 and 11-37-0, have a pH in the range of 6 to 7, these data indicate that concentrations of several heavy metals in phosphate fluid fertilizers could be reduced to very low levels by precipitation with inorganic sulfide reagents. The use of soluble sulfides to precipitate heavy metals from WPA has also been reported. Both Maruyama (14) and Berglund (15) have... 

Some ferrites that have been obtained by coprecipitation are shown in Table 3.2. Besides the preparation of powders for the ferrite industry, raw materials prepared by coprecipitation are used for the manufacture of pigments and magnetic toners and for the removal of heavy metal ions from waste water (Takada, 1982). 

Several investigations were carried out to remove toxic heavy metal ions from waste water by biosorption. Microbial cells loaded with heavy metals were recovered by flotation, e.g. Streptomyces griseus and S clavuUgerus loaded with Pb [108] and Streptomyces pilosus loaded with Cd [109]. In these flotation processes the microbial cells were dead therefore, they are not considered here. The removal of pyritic sulfur from coal slurries such as coal/water mixtures by Thiobacillus ferrooxidans and recovery of this iron-oxidizing bacterium by flotation is a special technique in the presence of high concentrations of solid particles (see e.g. [110]). The flotation of colloid gas aphrons was used for the recovery of yeast in continuous operation [ 111 ] for the recovery of micro algae, and in the presence of flocculants in batch operation [112]. These special techniques are not discussed here. 

Dr. B.R. Ambedkar National Institute of Technology -Jalandhar. Seven students have completed their Ph.D. degree under his supervision. He has a wide experience in the field of natural products, polymers composites, hydrogels, removal of toxic heavy metal ions from waste water, removal of colloidal particles, sustained drug delivery, controlled release of insecticides/pesticides, etc. He has more than 80 research papers in various reputed international journals. He has more than 60 research papers in the proceedings of the international conferences and... 

Heavy metals may be removed from waste water by photosensitisation using Ti02 where the metal is deposited on the surface of the photocatalyst ... 

Undissolved heavy metals have to be removed from waste water by physical methods (sedimentation, filtration, possibly flotation). Concentrations well below 0.5 mg/1 can be achieved by the use of these methods. 

Even when not specifically designed for the removal of heavy metals, some wastewater treatment processes remove appreciable quantities of the more troublesome heavy metals encountered in waste-water. Biological waste treatment effectively removes metals from water. These metals accumulate in the sludge from biological treatment, so sludge disposal must be given careful consideration. 

The U.S. Bureau of Mines-Salt Lake Research Center is conducting research to develop new biohydrometallurgical techniques to decontaminate mining and milling wastes containing heavy metals and toxic chemicals. Bacterial techniques are being developed to remove cyanide and selenium from waste water. 

Land disturbance and exposure of buried geologic strata to the open environment leads to sulfide oxidation (if present) and, as a consequence, water-quality degradation of runoff. For water-quality-control purposes, sedimentation ponds required by law are used as water treatment basins. Often, the pH of such basin waters is below 6, and the concentration of heavy metals is above acceptable levels. Water treatments include neutralization and removal of heavy metals as precipitates. Similar water-quality problems arise from other industrial sources, including heavy steel industries, electronics, food processing, mineral processing, and waste-disposal leachates. This portion of the chapter deals with some of the chemical agents used for neutralization purposes and some of their limitations. 

Dean JG, Bosqui FL, Lanoveite KH. 1972. Removing heavy metals from waste water. Environ Sci Technol 6 518-522. 

WI Starch Xanthate. Research by Wing and others (22, 27-29) has shown that water-soluble (WS) starch xanthates, in combination with cationic polymers to form polyelectrolyte complexes, can effectively remove heavy metals from waste water. To eliminate the expensive cationic polymer and give a more economical method of heavy metal removal, further research by Wing and others (12,30-33) showed that xanthation of a highly crosslinked starch yields a water-insoluble (WI) product that is effective in removing heavy metals from waste water without the need for a cationic polymer. In more recent work, Tare and Chaudhari (34) evaluated the effectiveness of the starch xanthate (WS and WI) process for removal of hexavalent chromium from synthetic waste waters. 

Mitchell, G. D. Total removal and recovery of heavy metals from waste water. Institute for Interconnection and Packaging of Electronic... 

Large quantities of sedimentary zeolites are known in the western United States (1). One of the more attractive of their potential uses is as an inexpensive, cation-exchange material for metals in environmental improvement. This use includes the removal of heavy metal ions from acid mine-drainage waters and the treatment of industrial waste solutions. Inasmuch as solutions containing unprecipitated heavy metal ions are typically acidic, the stability of zeolites in an acidic environment is an important consideration in evaluating their potential as a cation exchanger in such systems. 

Waste water treatment Recovery of heavy metal ions from effluent of the galvanizing process,36 treatment of waste from galvanizing baths (Cr, Zn, etc.),37 recovery of precious metals, regeneration of chemical plating baths,38 removal of radioactive elements,39 removal of ions such as chloride ions from a Kraft pulp mill,40 completion of closed system of waste water in factories,41 treatment of adsorption solution of flue gases,42 removal of salt from landfill leachate.43... 

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