Heavy metals simultaneous removal

SESR is applicable for soils contaminated with petroleum hydrocarbons, polychlorinated biphenyls (RGBs), and pentachlorophenol (PCP). The technology has been demonstrated to fix heavy metals and remove hydrocarbon contaminants simultaneously. After treatment, soluble salts can be leached from the dried, agglomerated soil. 

The modification of the sand surface allows the grains to simultaneously adsorb soluble heavy metals and remove particulate metals by filtration in a column packed with the media. Important factors to the performance of the adsorbent include pH of the solution to be treated, empty bed detention time (EBDT), and the presence of complexing agents, oil, surfactant, and biodegradable substances. 

Miretzky, P., Saralegui, A., and Fernandez Cirelli, A., Aquatic macrophytes potential for the simultaneous removal of heavy metals (Buenos Aires, Argentina), Chemosphere, 57 (8), 997-1005, 2004. 

The heavy metals copper, manganese, cobalt and zinc were omitted individually and in combination from MS and B5 media to determine the effect on antibody stability in solution [63]. When IgG, antibody was added to these modified media in experiments similar to the one represented in Figure 2.2, only the B5 medium without Mn showed a significant improvement in antibody retention relative to normal culture media. Nevertheless, protein losses were considerable as only about 30% of the added antibody could be detected in the Mn-free medium after about 5 h. The beneficial effect of removing Mn was lost when all four heavy metals, Cu, Mn, Co and Zn, were omitted simultaneously. The reason for these results is unclear. Addition of the metal chelating agent ethylenediaminetetraacetate (EDTA) had a negligible effect on antibody retention in both MS and B5 media [63]. 

V. C. Gopalratnam, G. F. Bennett, and R. W. Peters, The simultaneous removal of oil and heavy metals from industrial wastewater by joint precipitation and air floatation. Environ. Prog. 7, 84-92 (1988). 

C. C. Nesbitt and T. E. Davis, Removal of Heavy Metals from Metallurgical Effluents by the Simultaneous Precipitation and Flotation of Metal Sulfides Using Column Cells, in Extraction and Processing for the Treatment and Minimization of Wastes, J. Hager, B. Hansen, W. Imrie, J. Pusateri, and V. Ramachandran (eds.), TMS, Warrendale, PA, 1994, pp. 331-342. 

Barnes, L. J., Janssen, F. J., Sherren, J., Versteegh, J. H., Koch, R. O. and Scheeren, P. J. H. (1992). Simultaneous removal of microbial sulphate and heavy metals from wastewater. Trans. Inst. Mining Metall. 101, 183-190. 

The process of SO2 removal on activated coke followed by a simultaneous reduction of NO with ammonia has been successfully applied in industry [176]. Mitsui Mining Process [177] (Table 12) and the Sumitomo Heavy Industry Process [178] are examples of the simultaneous desulphurization and NO removal with the application of moving beds of carbon adsorbents. Apart from the two above mentioned target gases, these processes also exhibit high removal efficiency for heavy metals and dioxins. Removal of NO on activated carbons can also be carried out using two separate processes. As NO2 can be easily removed from gas streams by water, low-temperature oxidation of NO to NO2 on the porous carbon surface is considered as feasible for the removal of NO without the ammonia addition [179]. 

Simultaneous removal of heavy metals and nitrate. In addition to denitrification, the above series of columns were also used for the removal of heavy metals. A decrease in the denitrification capacity of the column was used as an index of the critical heavy metal concentrations causing toxicity to the P. aeruginosa. The toxic effect of metals (lead, chromium, copper, cadmium and zinc) was examined in a separate study (unpublished data). Of these metals copper proved to have the highest toxicity as it fully prevented denitrification in a very short time at a concentration of 10 ppm. Regarding their toxic effect the next in order was lead, followed by cadmium, zinc, and chromium. 

Fixed-bed bioreactors, using Immobilized P. aeruginosa cells are suitable for the simultaneous or separate removal of nitrates and heavy metals from very diluted solutions. The availability of a large amount of plastic waste makes it attractive as a cheap carrier for waste removal. The choice of plastic depends on the intended application for denitrification PVC is adequate (maximum viability of cells but less stability), for Pu removal PP is better (maximum stability, lessened viability). The plastic based bioreactors are highly competitive with others both in performance and in economy. 

For the simultaneous removal of organic compounds, these compounds are solubilized using different solubilizing agents (surfactants, cosolvents, and cyclo-dextrins). They are then transported and removed mainly by the electroosmosis process. It is essential to maintain all of the contaminants in soluble form and maintain electro-osmotic flow for the removal of both heavy metals and organic compounds. 

Sequential approaches are developed where (a) anionic metals are removed first and then cationic metals when mixed metal contamination is present and (b) organic compounds are removed first followed by the removal of heavy metals when coexisting heavy metal and organic contaminants are found. For example, the simultaneous electrokinetic removal of inorganic and organic pollutants (SEKRIOP)... 

For some combinations of heavy metals, it is also necessary to use enhancement solutions to ensure the simultaneous removal of all pollutants (Ottosen et ai, 2003). Especially, the presence of As in the soil necessitate alternative solutions to the acidic front since As generally has low mobility under acidic conditions, whereas As is more mobile under alkaline conditions, where most heavy metals are not mobile (Le Hecho, TelUer, and Astruc, 1998 Ottosen et aL, 2000). Le Hecho, Tellier, and Astruc (1998) conducted laboratory experiments with spiked soils, where the pollutants were As and Cr. Successful remediation was obtained in the developing alkaline front combined with the injection of sodium hypochlorite. As was mobile in the alkaline environment, and Cr(III) was oxidized to Cr(VI) by hypochlorite and mobilized in the alkaline environment. In loamy sand polluted with Cu and As from wood preservation. As and Cu were mobile simultaneously after the addition of NH3 to the soil (Ottosen et a/., 2000). As was mobile due to the alkaline environment and Cu formed charged tetra-ammine complexes. For the simultaneous mobilization and electrochemical removal of Cu, Cr, and As, ammonium citrate has shown to be successful (Ottosen et al, 2003). 

Maturi K, Reddy KR (2006). Simultaneous removal of organic compounds and heavy metals from soils by electrokinetic remediation with a modified cyclodextrin. Chemosphere 63(6) 1022-1031. 

Based on the laboratory experimental and field application results, electrokinetic remediation technology has been shown to be a promising method for simultaneously recovering multiple metal contaminants. However, the process is accompanied by limitations on the removal of several specific heavy metals. In this last section, the previous investigations, which focused on the removal of heavy metals, including Cr, As, and Hg, will be examined in more detail. Heavy metals have some reasonable properties, which should be considered more specifically ... 

The potential of electrokinetic remediation technology has been demonstrated for the remediation of mixed metal-contaminated soils, sediments, and groundwater over the past decade. Various enhancement schemes have been developed by the laboratory experimental and field applications, such as electrolyte conditioning and electrodialytic remediation. Despite such advances in the technology, it still has some limitations on the removal of mixed metal contaminants, including several specific heavy metals such as Cr, As, and Hg. Finding a simultaneously applicable process for the remediation of mixed heavy metals wUl require further study. 

Elektorowicz and Hakimipour (2001,2003a) presented a technology that permitted the simultaneous removal of heavy metals and PAHs from natural soil called Simultaneous Electrokinetic Removal of Inorganic and Organic Pollutants (SEKRIOP). This technology used EDTA for metal mobility and zwitterionic surfactants for hydrocarbon mobility. Furthermore, the application of cationic reactive membranes permitted capturing free metallic ions generated by electrokinetic phenomena before their precipitation in the cathode area. The capture of metal-EDTA complexes was done on anionic reactive membranes. 

The simultaneous introduction of several conditioning liquids presents a challenge, particularly in clayey soils. Elektorowicz and Hakimipour (2003a) designed a system for the simultaneous desorption of heavy metals and PAHs, their simultaneous transport through the clayey soU, and removal. The system included the simultaneous utilization of a surfactant, a chelating agent, and special electrode supply/removal systems in combination with electrokinetic transport. 

The results showed that the application of the multifunctional method SEKRIOP to clayey soil permitted the simultaneous removal of heavy metals (Pb, Ni) and PAH (phenanthrene) in situ. The removal was observed in all cells including the control cell (Table 15.2). However, the removal percentage [normalized calculations expressed as the final concentration C (mg/kg) to the initial concentration Co (mg/ kg)] varied due to the different response of physicochemical processes, which were different in each cell. 

Considering the effectiveness of the simultaneous heavy metals and PAH removal, it can be concluded that SEKRIOP might be used for an electrokinetic in situ remediation of mixed contaminated soils. The development of the above-described multifunctional method permits remediating the soils, particularly those characterized with low permeability. The results from the research can be applied to various municipal and industrial sites containing petroleum products and heavy metals. 

SEKRIOP technology is capable of the simultaneous removal of heavy metals and organic pollutants using a multifunctional electrode system. 

Reddy and Karri (2008b) also reported research investigating Fenton-like oxidation coupled with EK remediation of low-permeabiUty soils contaminated with both heavy metals and PAHs. That study examined the simultaneous oxidation of organic contaminants and removal of heavy metals. Kaolin spiked with nickel and phenanthrene each at a concentration of 500mg/kg of dry soil to represent typical heavy metal and PAH contaminants found at contaminated sites. Four-week lab-scale EK... 

EDTA-enhanced electrokinetic high removal efficiency of only Cr in high pH Enhanced by various electrolyte solutions simultaneous removal of multiple heavy metals NaCl/EDTA or acetic acid Different removal efficiency depending on scale bench scale < field scale field scale 78% Cr, 70% Cd after 6 months... 

In a recent study, we proposed a new method (competitive adsorption method) for the removal of toxic heavy metal ions from acid-sensitive biomaterials, and applied it to the removal of cadmium from the MG of the scallop Patinopecten yessoensis [54]. In this method, a competitive adsorbent (IHA) is added to a weakly acidic solution containing MG to lower the cadmium concentration in the liquid phase. The lowering of the cadmium concentration in the liquid phase promotes the release of cadmium ions from MG, and the released cadmium ions are immediately adsorbed by IHA. In this manner the competitive adsorption method enables the simultaneous removal of cadmium from the scallop midgut and from the liquid phase under mild acidic conditions. 

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