Study On Biological Treatment Of Excess Xanthate In Floatation Wastewater

With the development of mining industry, the environmental problems caused by mineral processing has caught people’s attention, mineral processing waste water treatment has become an important part of environmental remediation. Many physical and chemical methods such as coagulation and sedimentation, oxidation and agent neutralizationare widely used. However, among these, some can not play its role due to the limitation of cost and technology.Taking the actual condition that low concentration of xanthate, heavy metal ions and some agents, such as foaming agents, activators and inhibitors coexisting in floatation wastewater into consideration, the effects of co-metabolism substrates, nitrogen sources, C/N ration, metal ions (Fe3+, Zn2+ and Pb2+) and co-existing agents on microbial degradation of xanthate were investigated. Starch, sucrose, glucose were selected as co-metabolism substrates Ammonium chloride, urea, yeast extract, sodium nitrate and sodium nitrite were used as nitrogen sources. The shaker culture was applied in this study, floras which could degrade xanthate wereselected and acclimated.At the same time, the biofilm reactors were built by bagasse, biodegradable resin-poly butylene succinate (PBS), activated carbon and rice husk which served as biofilm suspended carriers. In biofilm reactors, the effects of different carriers on xanthate biodegradability was detected, the effects of biofilm EPS concentration and its composition on biochemical degradation xanthate was also explored, finally the changing of the material in the process of xanthate biodegradation was deduced. The results in this study were showed as follows:(1) Xanthate degradation could occur under natural conditions,at the starting, the degradation rate was very slow, with the increasing of time it become fast.In general, the speed of degradation is slowly. At lower the pH value, the natural degradation of xanthate was more stronger. With thedomesticatedxanthate degrading bacterias,the speed of xanthatedegradation was significantly accelerated, and degradation efficiency was significantly increased.The growth and reproduction rate of xanthate degrading bacteria was consistent with the degradation rate of xanthate.It indicated that the domesticated microorganism plays an important role in the degradation of xanthate. Higher pH value promote the microbial degradation of xanthate, within the pH range of 6 to 10. However, the biochemical degradation rate was not evidently variousat different pH, andthe effluent is a little alkaline.With the presence of microorganisms, pH of the solution change to neutral in the degradation of xanthate which maybe due to the products of xanthate degradation and the regulation of microorganisms, co-metabolism substrates enhance the biodegradation of xanthate.However, the enhancement vary due to the difference in chemical structure and is in the order:Starch>sucrose>glucose, Polysaccharide is better than monosaccharide. Starch is the most appropriate co-metabolism matrix. Ammonium chloride and urea is better because of high nitrogen contain in them, followed by yeast extractin which more nutrients contained but fewer nitrogen,The nitrogen in sodium nitrate and sodium nitrite is difficult to be used by this mixed species. Higher C/N ration is in favor of biodegradation of xanthate.(2)With the additionof Fe3+ranged from 0 to 20 mg/L, the microbial degradation of xanthate was enhanced. 10mg/L of Zn2+slightly increased the biodegradation, while at 20mg/L the effect was not significant, and the biodegradation is inhibited at the range of 30～-50 mg/L. Pb2+was inhibitory to microorganis,4 mg/L of Pb2+ inhibited the biodegradation of xanthate, the inhibition became more evident with the increasing of Pb2+concentration. Saponifier.flotation oil, high concentrations of sodium sulfide and zinc sulfate inhibitedthe biodegradation of xanthate. the inhibition became more obvious with the increasing of concentration. But the effect of low concentration of sodium sulfide and zinc sulfate on biodegradation of xanthate was not significant. In degradation progress, the higher the concentration of saponifier and zinc sulfate,the more obvious inhibition.The impact of flotation oil and sodium sulfide flotation became weaker at the late of degradation. Influence of aponifier and flotation oil alone was more significant than the activator sodium sulfide, and with the increasing of drug concentration, the degradation rate of xanthate became weaker, The effect of zinc sulfate is stronger than flotation oil. The combined effect of coexistence agents were different because of the interaction.The combined effect of zinc sulfate and saponification which was stronger than the influence of each alone, apart from this, other remaining agents madethe inhibition weaker because of the interaction between them.The UV scanning spectrum of xanthate biodegradation process is different in the case of the presence of different agents.The presence of carbon disulfide was maximum accumulation undr saponifier, and hydrogen sulfate absorption peaks occurredat the presence of an activator sodium sulfide.(3) Bagasse, PBS, activated charcoal and rice husk was used as a biofilm reactor carriers which supplied a stable biofilm growth and play a role of degradation. Compared to the suspended growth systems,the biochemical degradation of xanthate becamesignificantlyin biofilm systems. Bagasse as the carrier which can provide better co-metabolism carbon as well, and in favor of the growth of bacteria which can degradate xanthate. What’s more,it havegreater biomass, higher EPS content and PN/PS values, soit is conducive to the degradation of xanthate inbiofilm reactor.EPS concentration, polysaccharide, protein ratio and carbon disulfide were diferent, becaule of the diversity of physicochemical properties of the carriers in biofilm reactor, but the products isthe same in degradation process. The EPS concentrationand proportion of protein were higher in biofilm reactor with a ctivated carbon and bagasse as carriers, and its speed of xanthate biochemical degradation is fastest.