Mechanisms of the effect of modified phosphogypsum on the change of heavy metal migration from sludge
This study utilized a mixture of potato residues and phosphogypsum waste residue to prepare a dual-modified material(D-MPR),which was then used to treat heavy metals in sludge.The preparation conditions of the dual-modified material were studied,along with its effects on the Zeta potential of the sludge,extracellular polymeric substances(EPS),and the migration of heavy metals;the ecological risk of heavy metals in the treated sludge was analyzed,and a heavy metal migration model was constructed.Experimental results showed that the waste residue(PR)underwent etherification modification at an alkalization temperature of 50°C with 2%hexadecyl trimethyl ammonium bromide(CTAB)by PR mass,at an etherification temperature of 50°C for 3hours;subsequently,by adding 1%PR of ammonium persulfate and 80%PR of acrylamide(AM),and reacting at 50°C for 3hours for graft modification,D-MPR was prepared.By adding D-MPR at a proportion of 12‰ of the dry solids(DS)amount of the sludge to treat heavy metals,it was found that compared with the original sludge,approximately 42.43%of non-stable Cd,60.42%of non-stable Cr,53.10%of non-stable Cu,67.58%of non-stable Pb,55.21%of non-stable Zn,34.23%of non-stable Ni,and 74.68%of non-stable As were immobilized into the sludge cake,significantly reducing the migration risk and potential ecological risk coefficients of heavy metals in the sludge cake.Furthermore,the study found that the conversion rate of non-stable heavy metals decreased with an increase in LB-EPS and TB-EPS content,and increased with an increase in Zeta potential,thereby establishing a conversion model for non-stable heavy metals.This research provides a solid research foundation for the study of sludge heavy metal treatment with solid waste-based materials and has significant practical importance for the detoxification of sludge.
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