Heavy metals removal processes

Wing, R. E. and Rayford, W. E. (1978), Heavy Metal Removal Processes for Plating Rinse Waters, Proceedings of the 32nd Industrial Waste Conference, May, 1977, Purdue University, Ann Arbor Science, Ann Arbor, Michigan, pp. 838-52. 

For metal desorption from the biomass certain dilute solutions of mineral acids like hydrochloric acid, sulfuric acid, acetic acid and nitric acid were used [219, 76]. Batch system was carried out to study the desorption of the adsorbed Hg (II) from the biosorbent - immobilized and heat inactivated Trametes versicolor and Pleurotus sajur-caju [8]. Hg (II) ions adsorbed onto the biosorbents were eluted with 10 mmol dm HCl and the results showed that more than 97% of the adsorbed Hg (II) ions were desorbed from the biosorbents. In order to evaluate the feasibility of applying the prepared biosorbents in the heavy metals removal processes, the metal desorption efficiency from loaded biosorbents, and the reusability of the biosorbent in repeated adsorption-desorption operations were determined. The charged species exhibited desorption-resistance fraction whereas the desorption of the neutral form was completely reversible. The difference in sorption and desorption between the neutral and charged species is attributed to the fact that the anionic species sorbs by a more specific exothermic adsorption reaction whereas the neutral form partition by the hydrophobic binding to the soil [206]. Desorption of soil-associated metal ions and possible mechanisms have received considerable attention in literature [148],... 

Biosorption is a process that utilizes biological materials as adsorbents [Volesky, 1994], and this method has been studied by several researchers as an alternative technique to conventional methods for heavy metal removal from wastewater. 

Reverse osmosis and nano-filtration are high-pressure membrane separation processes (typically 10 to 50 bar for reverse osmosis and 5 to 20 bar for nano-filtration), which can be used to reject dissolved inorganic salt or heavy metals. The processes were discussed in Chapter 10 and are particularly useful for removal of ionic species, such... 

Normally, treatment of coproduced groundwater during hydrocarbon recovery operations will include, as a minimum, oil-water separation and the removal of dissolved volatile hydrocarbon fractions (i.e., benzene, toluene, and total xylenes). In addition, removal of inorganic compounds and heavy metals (i.e., iron) is often required. Dissolved iron, a common dissolved constituent in groundwater, for example, may require treatment prior to downstream treatment processes to prevent fouling problems in air-stripping systems. Heavy metals removal is normally accomplished by chemical precipitation. 

Alternative 1 consists of preliminary treatment for heavy metals removal with the primary concern being iron removal (Figure 8.3). The levels of iron observed in the groundwater at this site would be very detrimental to the downstream treatment processes. This pretreated water would then be used for cooling tower makeup water followed by biological treatment. This approach would be the easiest and cheapest alternative. This combined process should provide effective removal of BTEX. 

Heavy metals such as copper, zinc, lead, nickel, silver, arsenic, selenium, cadmium and chromium may originate from many sources within a rehnery and may, in specihc cases, require end-of-pipe treatment. Some agencies have set discharge limits that are beyond the capability of common metals removal processes such as lime precipitahon and clarihcation to achieve. Other treatment processes such as iron coprecipitation and adsorption, ion exchange, and reverse osmosis may be required to achieve these low effluent concentrations [52]. 

T0235 Electrochemical Treatment of Contaminated Ground Water—General T0279 Environmental Research and Development, Inc., The Neutral Process for Heavy Metals Removal... 

HPT Research, Inc., has developed the ionic state modification (ISM) process for the treatment of acid mine drainage (AMD). ISM is an ex situ treatment technology that uses magnets, electricity, and proprietary chemical to precipitate heavy metals, remove sulfate ions, and neutralize acidity from AMD and industrial wastewaters. The end products of the process are a metal hydroxide sludge, a calcium sulfate sludge, and treated liquid effluent. The vendor claims that the metal hydroxide sludge may have some value as an ore, the calcium sulfate may be used as an agricultural additive to soils, and the liquid effluent is free of metal contamination and has low sulfate concentrations. 

Andco Environmental Processes, Inc., "Andco Heavy Metal Removal Systems, Actual Performance Results. ... 

Brantner, K., and Cichon, E., (1981) "Heavy Metals Removal Comparison of Alternative Precipitation Processes. Proc 13th Mid-Atlantic Industrial Haste Conf., 13 43-50. 

A complete process scheme for regeneration and reuse of spent final rinse water from an electroless plating operation has been developed by Wong et al. [105]. It includes (i) pre-treatment by microfiltration, UV irradiation, carbon adsorption (ii) heavy metal removal by nanofiltration and (iii) polishing using an ion exchange mixed bed. The results of a pilot study showed that high quality product water with an overall water recovery of 90% could be produced with an estimated payback period of less than 18 months. 

The application of natural zeolites in heavy metal removal is described now. The methodology consists of the development of a process for heavy metal removal from wastewater using dynamic ion exchange in natural zeolite columns [38,53],... 

Examples of sorption processes using packed beds include recovery of crude antibiotics from fermentation broth filtrate, heavy metal removal from product streams, and separation of amino acids from solutions. 

Lead A heavy metal removed by the refining process. 0.1 mg/kg max... 

Fig. 11 A conceptualized continuous decontamination process for heavy-metal removal from a sludge reactor using CIM.

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. 

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