Method For Malachite Green Removal By Enhanced Precipitation Of Calcium Oleate And Microbial Flocculant GA1 Flocculation

With the rapid development of textile industry,The toxic dyestuff wastewaters from the production and use of dyes are often released into the environment without any prior treatment.On the one hand,the dyestuff wastewaters would deleteriously impact the aquatic life by reducing the penetration of light and oxygen,on the other hand would pose a threat to body tissue by the intense carcinogenesis,tetratogenesis and mutagenesis,and in severe cases would endanger human life.Malachite green?MG?,a cationic azo dye,was widely used in producing paper,leather and pharma-ceutical products,textile industry,food additive and commercial aquaculture filed.Malachite green have been shown to be toxic to liver,kidney,digestive tract and other organs of aquatic life and mammal.Hence,it is crucial to remove the dye of MG from effluents by taking the effective measures.This study developed a method containing calcium oleate?Ca?OL?₂?enhanced precipitation and microbial flocculant GA1?MBFGA1?flocculation to remove mala-chite green?MG?,a cationic dye,from aqueous solution.This method combined the solubilization effect of sodium oleate?NaOL?micelles on MG and the Ca²⁺effect on NaOL micelles including the solubilized MG?NaOL-MG micelles?to make MG se-parated out from aqueous solution in a form of MG loaded calcium oleate particles?Ca?OL?₂-MG particles?,which then were flocculated and settled out by MBFGA1.In this way,MG was removed from aqueous solution.This study researched the effects of factors,including NaOL,Ca²⁺,and MBFGA1 dosage,MG initial concentration,rapid mixing time and slow mixing time on the MG removal.Meanwhile,the inde-pendent and interactive effects of factors,such as NaOL,Ca²⁺and MBFGA1 dosages,on the interaction between NaOL and Ca²⁺and the removal of MG were studied.Fi-nally based on these investigations,MG removal mechanism and the interactive me-chanism between NaOL and Ca²⁺were discussed and confirmed by environmental scanning electron microscope?ESEM?and Energy dispersive spectrometer?EDS?analysis.Under the optimum conditions of MG initial concentration 50 mg·L^-1,NaOL do-sage 9 mmol·L^-1,Ca²⁺dosage 9 mmol·L^-1,MBFGA1 dosage 4 mL,5 minutes rapid mixing at 200 rpm and 30 minutes slow mixing at 40 rpm,experimental results sug-gested that the MG removal rate would acquire 98.13%.These results showed that the method was highly efficient and environmentally friendly,and would not cause sec-ondary pollution.Through independent and interactive effects analysis of important factors on MG removal rate and the flocs analysis by the ESEM and EDS,we could speculate that the interaction between Ca²⁺and NaOL mostly relied on the relative concentration of Ca²⁺and NaOL.Only when Ca²⁺dosage was relatively enough,High MG removal rate would be acquired.In the overall system,when Ca²⁺dosage was relatively excess,in the function of Ca²⁺dosage,the Ca²⁺would react with NaOL micelles including the solubilized MG?NaOL-MG micelles?to generate MG loaded calcium oleate particles?Ca?OL?₂-MG particles?.With the flocculation of MBFGA1,MG was removed in a form of Ca?OL?₂-MG particles.Nevertheless,with continued increase of Ca²⁺dosage,when NaOL dosage was excessive relatively,the formation of NaOL micelles would continually solubilize the majority of MG molecules adsorbed on the Ca?OL?₂-MG particles,which would greatly cause the decrease of MG removal rate.Method containing calcium oleate enhanced precipitation and microbial floccu-lant GA1 flocculation to remove malachite green had the advantages of high efficient,convenient operation,environment friendly,and so on.And it seemed to hold strong applied potential to the treatment of real dye wastewater.