Removal Of Metal Pollutants Research Articles

ARSENIC CONTAMINATION: SOURCES, EXTENT AND IMPACT ON THE ENVIRONMENT

Arsenic (As) is a heavy metalloid with emanating concern of its environmental toxicology worldwide. Arsenic is released into the living environment via natural and anthropogenic sources. Natural phenomena include dust storms, forest fires, volcanic eruptions, hydrothermal activities, pedogenesis and geothermal activities. Agricultural inputs like chemical fertilizers and pesticides, dumping of municipal wastes, addition of untreated effluents resulting form industrial activities into the surroundings, smelting, mining, cement manufacturing, coal burning and disarmament of the chemical weapons are considered as human activities. The potential threat of Arsenic is extended over 105 nations and 226 million populations on a global scale. As contamination in soil and groundwater is the major route for human exposure. Many parts of the world have been reported As levels exceeding the threshold limits for soil as well as groundwater. The chemical similarity of arsenate and phosphate facilitate the entry of As into plants and disrupt the metabolic and physiological pathways. Apart from its carcinogenic risk, chronic exposure leads to arsenicosis and other disorders. Phytoremediation and microbial remediation are environmental friendly and cost effective technique for As removal and nanotechnology is an emerging technology with wide application in removal of metal pollutants from the contaminated site.

Effects of algal-bacterial ratio on the growth and cadmium accumulation of Chlorella salina-Bacillus subtilis consortia.

Algae-bacteria consortia have been proven effective in the removal of metal pollutants, but the effects of algal-bacterial ratio in the metal accumulation and resistance by this symbiotic system have not been systematically investigated. In this study, we set up consortia with various ratios of Chlorella salina-Bacillus subtilis, determined their growth, Cd accumulation, levels of intracellular glutathione (GSH), extracellular polysaccharide, phosphorus (P) in the culture medium, and functional groups of consortia after Cd treatments (0.1, 0.5, 1 mg L-1 ) for 7 days. With the addition of B. subtilis in the C. salina culture, the dry weight and specific growth rate of the consortia significantly increased compared with C. salina alone, reaching 68.33 mg and 0.382 (mg L-1 ) d-1 respectively at the 1:4 algal-bacterial ratio with 1 mg L-1 Cd treatment. Maximum Cd removal (51.66%) was also observed upon the same Cd exposure and algal-bacterial ratio. Cadmium was mostly taken up into cells at 1 mg L-1 Cd whereas its adsorption dominated the accumulation when Cd was 0.1 and 0.5 mg L-1 . The amounts of extracellular polysaccharides, GSH, and P of the symbiotic system were also increased by the bacterial addition. Besides, Fouriertransform infrared (FTIR) spectroscopy analysis showed that functional groups like N-H, O-H, and P-O-C were involved in the Cd complexation. Taken together, a higher bacterial ratio promoted the Cd accumulation and detoxification by the C. salina-B. subtilis consortia through intra- and extracellular processes.

Synthesis and Electrochemical Application of MxFe3-XO4 (M=Cu,Co) for the Detection and Removal of Metal Pollutants

Over the last two decades, nanomaterials (metallic nanoparticles, carbonaceous nanostructures) have triggered great interest thanks to their specific physic-chemical properties. The improvements they have made in the field of electro-analysis are numerous. Thus, a wide range of physic-chemical technologies based on the use of inorganic materials for the detection and removal of water pollutants has become a promising voice. In this context, we were interested in the design of electrodes modified by nanomaterials of the spinel type CxFe3-xO4 for the detection and quantification of metallic micro pollutants in water. The phases of the spinel system were synthesized by the sol-gel method, and physic-chemical characterization was performed by ATD-TG, DRX and MEB. The methods used for the electrochemical test are cyclic voltammetry (CV), square wave voltammetry (SWV) and impedance spectroscopy (EIS).The results of the physic-chemical analysis of the oxides showed that the phase is obtained at a calcination temperature of 600°C, and the electrochemical tests of the elaborate electrode revealed a very high sensitivity to ions (Mn2+, cd2+, pb2+, Hg2+). Keywords: nanoparticles, spinals, metal pollutants, modified electrode, electrochemical tests.

Removal of Metal Pollutants (Cd(II) and Cr(III)) from Phosphoric Acid Solutions by Chelating Resins Containing Phosphonic or Diphosphonic Groups

In this study, chelating ion exchangers containing phosphonic (−PO(OH)2) acid groups (RSPO, Diaion-CRP200) and the new chelating resins (Diphonix) containing sulfonic and gem-diphosphonic acid groups chemically bonded in a styrene−divinylbenzene polymeric network have been investigated for sorption of Cd(II) ions from phosphoric acid solutions. Comparison of acid dependencies of Cd(II) uptake measured with that obtained using a commercial sulfonic acid type ion-exchange resin (Dowex 50W(X8)) and a solvent containing resins (Actinide-CU) has been performed. The resin Diphonix has been employed for columnar sorption of Cd(II) and Cr(III) ions from phosphoric acid solutions.