Effects Of Butyl Xanthate On Microbial Toxicity And Nickel Speciation In Soil

With the rapid development of the economy in recent years,the scale of the mining industry has expanded.Butyl xanthate is a typical flotation reagent for nickel(Ni²⁺)sulfide ore and has been used in large quantities during the flotation process.However,due to the lack of regulatory measures,large amounts of butyl xanthate and nickel released into the environment may form secondary products,which may cause serious damage to the ecological environment.Therefore,the microcalorimetric method,soil enzyme activity measurements and the BCR sequential extraction method have been used to analyze the effects of combined pollution of nickel and butyl xanthate on microbial toxicology and heavy metal speciation in this study.The main findings are as follows:From the perspective of energy metabolism,the inhibition rate（I）of microbial activity increased with the increased dose of butyl xanthate or Ni²⁺.The I of butyl xanthate or Ni²⁺was continuously reduced during the research period,and contaminants stimulated microbial activity on the 180th day.The I of microbial activity decreased as butyl xanthate increased in the presence of same Ni²⁺concentration.In most of the time,the I of combined pollution on soil microbial activity was higher than that of Ni²⁺or butyl xanthate.As butyl xanthate is continuously degraded and utilized,its toxic effect was weakened,but the microbial activity was stimulated in the later stage.Butyl xanthate captured Ni²⁺to form a complex,which in turn altered the toxicity to soil microorganisms.From the perspective of soil enzyme activity,butyl xanthate inhibited urease and invertase activity,slightly stimulating FDA hydrolase activity in the early stage.Urease and FDA hydrolase activity decreased as butyl xanthate increased.Single Ni²⁺pollution and combined pollution had an inhibitory effect on these three enzymes,but the inhibition decreased.Under combined pollution conditions,butyl xanthate had a significant dose-effect relationship with urease.Especially on day 180,butyl xanthate,Ni²⁺and combined pollution significantly stimulated urease activity.Sensitivity of soil enzymes to contaminants is shown below:urease>FDA hydrolase>invertase.Urease activity was more sensitive than others,because contaminants affected the normal biochemical metabolism of microorganisms or directly damaged the structure of the enzyme.From the perspective of the Ni²⁺speciation,because of the aging effect of heavy metals,the exchangeable and reducible Ni²⁺in the soil gradually transformed into more stable forms with time.However,the percentage of exchangeable or reducible states in the combined pollution was higher than the single Ni²⁺pollution.The possible reason was that butyl xanthate reacted with nickel form a complex（nickel butyl xanthate）,which altered Ni²⁺speciation in the soil,which are increasing the potential ecotoxicity of Ni²⁺.Correlation analysis of different environmental biological factors showed that the exchangeable Ni²⁺（bioavailability）was the main factor determining soil microbial toxicity.