دانلود رایگان مقاله انگلیسی افزایش حذف فلزات سنگین از لجن در تصفیه الکتروکینتیک با بیوسورفکتانت ها - الزویر 2018

Abstract

High content of heavy metals in the sludge was the obstacle of sludge land application and resource recycling. In this work, rhamnolipid, saponin and sophorolipid were used to enhance heavy metals removal from the sludge in the electrokinetic tests. Also, the 0.1 mol L-1 HNO3 was used to control catholyte pH in the electrokinetic tests. The electric current with the duration time variation, sections pH and heavy metals residual concentrations with space and time variations were investigated in the electrokinetic tests. Results indicated that these three biosurfactants and catholyte conditioning (0.1 mol L-1 HNO3) could enhance heavy metals removal from sludge in the electrokinetic experiments. After EK experiments, Cu, Zn, Cr, Pb, Ni, Mn, Fe and Hg removal efficiencies in the enhanced EK experiment were higher than unenhanced EK experiment. Cu, Zn, Cr, Pb, Ni, Mn, Fe and Hg obtained an effective removal efficiency in the EK3 test, which were 55.8±5.46%, 73.8±6.23%, 64.0±5.11%, 51.6±5.32%, 60.8±2.12%, 56.0±3.21%, 41.0±2.12%, 35.0±2.12%, respectively. Heavy metals transferring toward the cathode were greater than anode, due to the free heavy metal ions and positively charged complexed heavy metal moved to the cathode chamber by electromigration. Rhamnolipid, saponin and sophorolipid can effectively enhance heavy metals removal from the sludge in the electrokinetic tests.

4. Conclusions

In this work, rhamnolipid, saponin and sophorolipid were used to pretreat the sludge, and the nitric acid was used to control catholyte pH in the EK tests, which were used to enhance heavy metal removal from the sludge in the novel enhanced EK technique. Results demonstrated that heavy metal can effectively remove from the sludge in the enhanced EK tests. Heavy metals removal efficiencies in the biosurfactants enhanced EK tests (EK3, EK4 and EK5) were higher than unenhanced EK (EK1) and acid-enhanced EK (EK2) tests. Rhamnolipid, saponin and sophorolipid have chelating and binding ability in acid conditions, these characteristics can enhance heavy metal removal from sludge in the EK tests. The positively charged metal-complexes and free heavy metal cation can migrate toward the cathode chamber by electromigration. The results demonstrated three biosurfactants can effectively enhance heavy metals removal from the sludge in the electrokinetic tests.