The Mechanism Of Arsenic Removed By Biologically Nano-FeS And Application

Arsenic?As?can be released into the environment by various ways,resulting in arsenic content increased in soil and water.As compounds have high toxicity and poses a serious threat to human health.In recent years,there are more and more researches of arsenic remediation in contaminated and water using nano-FeS particles.However,there are no previous studies on aqueous arsenic species and kinetics in As removed by biologically FeS particles,and the fate and transport of As associated with nano-FeS particles in the natural environment is poorly understood.In this work,we synthesized biologically nano-sized FeS by Fe reducing bacteria?JF-5?and sulfate reducing bacteria?SRB?,investigated the removal of As and in aqueous solution and analyzed the adsorption performance and mechanisms of biologically FeS to As.Explored the release of adsorbed As on biologically FeS in different environment geochemical conditions.?1?The biologically nano-sized particles was synthesized by two reducing bacteria,it was mainly composed of amorphous mackinawite(FeS_0.9).The surface area was 45.1 mg/g.The kinetics results showed that the efficiency of removed by biologically FeS depended on pH,and the best removal occurred at pH 5;the reaction reached equilibrium in 240 min.Due to the horizontal oscillation accelerated the FeS particles rapidly settled,the efficiency of removal decreased with increasing solid/solution ratio;the adsorption kinetics followed the pseudo-second-order model and the isotherm followed by Langmuir equilibrium for different solid/solution ratios.The maximum sorption capacities were 218.5 mg/g.The mechanism study revealed that the FeS particles dissolved and released S^2-,which could reduce As???to As???and other lower valence,subsequently removed arsenic by adsorption or complexation.?2?Based on the potential hazards of the products from arsenic removed by biologically FeS under different environment geochemical conditions are incompletely known.This work investigated the effect of pH,Fe³⁺and H₂O₂ on the stability of FeS-As???solid.The dissolved As species in the solutions was As???at pH 3,where about 25%As???were released from FeS-As???solid,however,about 45%As???released at pH 9.The dissolved As??/??were lower at the coexist of Fe³⁺,only little occurred in the low concentration experiment.Similar trend showed in H₂O₂ experiments,but about 5.8%As???and 20.3%As???were released from the FeS-As???solids.The dissolved kinetics of nano-FeS containing As showed that the dissolution was highly depended on pH,the rate of dissolution rapidly increased before 2 h and gradually decreased after the time at pH 3 and pH 9.High concentration of Fe???and H₂O₂ could restrained the released of dissolved As,due to the formation of iron?hydroxide?oxides.