The Study of Bioremediation on Heavy Metal of Cultured Seawater by <i>Sphingomonas sp. XJ2</i> Immobilized <i>Sphingomonas</i> Strain

Abstract

Listen

Translate article

In this study, the bacterium was identified as Sphingomonas sp. XJ2 by means of microscopic examination, physiological, biochemical detection, and modern molecular biology technology. After acclimatization for several times, this bacterium has good performance in removing heavy metals and organic matter from seawater. Alginate immobilized cells has obvious holes on the surface and has big specific surface area, which are conducive to the adsorption of metal ions. Hydration heat of Pb2+ is small, and is most likely to drop out of ligand water then become exposed Pb2+; in addition, the ionic radius of Pb2+ and is very similar to the ball K+ and is adsorbed by the ball easily. FTIR and XPS study indicated that Pb (II) was complexed by C-H and C-O bonds. The concentration of Pb(Ⅱ)of mine wastewater reach the first class of irrigation water quality standards after the first time of adsorption treatment, and reach the first class of fishery water quality standard after the second treatment. 1． Introduction Mine waste water mainly comes from mine production, the main pollutants including heavy metals, acid, organic pollutants, oil pollutants, cyanide, fluoride and soluble salts and so on. Heavy metal pollution and acid pollution are the most common water pollutions, the mainly heavy metals from wastewater are lead, zinc, nickel, copper, mercury, chromium, cadmium, cobalt, manganese, titanium, vanadium and bismuth. Hazards of mine waste water including environmental degradation and toxic to organisms; mine waste water contains heavy metal ions and other metal ions, through infiltration, percolation and runoff channels walk into the environment, then pollute water. After precipitation, absorption, complexation, chelation and redox, migrate and change in the water, and ultimately affect human health and aquatic growth. Heavy metals and metalloids and other pollutants in wastewater once enter the water environment, they can not be biodegradable, but by precipitation - dissolution, oxidation - reduction, coordinate effect, colloid formation effect, adsorption - desorption process and a series of physical and chemical migration transformation, which will eventually as one or more form stay in the environment for a long term, causing permanent potentially damage [1]. How to prevent non-ferrous metal mine waste water polluting water and farmland is one of the current problems which arising large public attention. Traditional treat methods of heavy metal waste water are chemical precipitation, ion exchange, evaporation and electrolysis, etc., these methods have disadvantages of high investment and operating costs, precipitation removal is not satisfactory, and could easily lead to secondary pollution and other defects. Since 1980s, people began to turn to research microbial treatment of heavy metal waste water, and found that microbial treatment of wastewater had advantages of low cost, effective and no secondary pollution. The economical and ecological feasibility of biosorption processes depend on the biosorbent metal uptake capacity to reach metal concentration legal limits for wastewater discharge and the ability of eluants to release sequestered metal in subsequent recovery [2-4]. Recovery allows metal recycling, leading to energy savings and materials conservation[5]. Finally, biosorbent regeneration used in multiple adsorption–desorption cycles [6], contributes to process cost effectiveness. Living cells have so broad assortment of mechanisms for surviving in environment that have elevated metal concentrations, including transport and intracellular and extracellular sequestration .The active process of metal accumulation by cells is usually referred to as bioaccumulation, while the passive metal sequestration by cell components is generally called biosorption. The physicochemical basis for metal sequestration at the cell surface may include complexation, coordination, chelation, ion exchange, adsorption, and inorganic microprecipitation processes. Bacteria make excellent biosorbents because of their high surface-to-volume ratios. Metal-binding behaviour has been evaluated on the basis of bacterial cell Gram reaction for viable cells and cell walls and envelopes. In this study, we conducted separation domesticated culture to Sphingomonas sp. XJ2 and used them to treat waste water preliminarily. Establishing an efficient, cheap, adaptable and easy to operate way of treating non-ferrous metal mine wastewater is a new development.