Enhanced Remediation Of TBBPA-Cd Co-contaminated Soil Based On Sludge Hydrolysate

At present,the rapid development of industrial and mineral industry can cause serious soil pollution,in which surrounding soil shows a trend of combined pollution,while e-wastes dismantling facility is a typical polluted site with the combination of brominated flame retardants?BFRs?and heavy metals.Tetrabromobisphenol A?TBBPA?is one of the most extensively used BRFs all arould the world,which is recognized as a potential endocrine disruptors along with immunotoxicity,neurovirulence,etc.E-waste contains a lot of heavy metal contaminants,and the removal and processing of e-waste must be accompanied by heavy metal pollution,in which Cd contamination is particularly acute,which can enter human body via digestive and respiratory tract,even concentrate in body and threat human health.To the best of our knowledge,no previous study on TBBPA-Cd remediation was reported,therefore,this research has a widespread practical significance.In the present study,we first studied the remediation of co-contaminated soil in the presence of sludge hydrolysate.Results showed that the sludge hydrolysate contained protein-like and humic acids,etc.,which could complex with TBBPA and Cd?II?.As control we studied the enhanced remediation of TBBPA-Cd co-contaminated soil by bamboo biochar,while the adsorption of Cd?II?in the presence of bamboo charcoal is an endothermic and spontaneous reaction,the results of remediation of combined pollutant further showed that the bamboo charcoal could enhance the removal efficiency of TBBPA and the immobilization of Cd at the same time.The TBBPA removal efficiency?initial concentration,30 mg/kg?was 49.28% and the immobilization efficiency of Cd?initial concentration,5 mg/kg?was 16.75% upon the addition of 4 g/kg of bamboo charcoal after 15 days reaction.We green synthesized a mixture of submicro iron oxides on the basis of sludge hydrolysate.XRD results showed that the mixture of submicro iron oxides were Fe₃O₄.When the submicro iron oxides synthesized with optimized condition were introduced into the polluted soil,the removal efficiency of TBBPA was 53.5%,and the immobilization efficiency of Cd was 42.96% after 15 days reaction.Finally,the results of seed germination index demonstrated that the green synthesis of magnetic iron oxides could efficiently reduce the toxicity of polluted soil.We then investigated the mechanism of bacterial community-level changes during the process of TBBPA degradation.The results showed that the place of TBBPA degradation was located in extracellular and periplasmic fractions.The metabolites of TBBPA degradation were detected by using HR HPLC-LTQ-Orbitrap MS.Five main intermediates were obtained,including Tri-BPA,BPA,4-hydroxyphenylacetone,4-hydroxyphenylacetic acid,and phenylacetic acid.Therefore,based on the above five identified products,the possible pathway during TBBPA biodegradation was proposed,the first step is TBBPA debrominated to BPA stepwise,and the second step is aerobic mineralization of BPA by soil microorganism.