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Application and mechanism of polysaccharide extracted from Enteromorpha to remove nano-ZnO and humic acid in coagulation process

Sun, Jianzhang, Gao, Baoyu, Luo, Yuanxia, Xue, Moxi, Xu, Xing, Yue, Qinyan, Wang, Yan
Frontiers of environmental science & engineering 2018 v.12 no.3 pp. 11
Ulva, adsorption, algae, aluminum, chlorides, coagulants, coagulation, colloids, dissolved organic matter, heavy metals, humic acids, metal ions, nanoparticles, neutralization, pollutants, polysaccharides, turbidity, water treatment, zinc
Enteromorpha polysaccharide (Ep) extracted from alga a novel green coagulant aid for nanoparticles (NPs) and heavy metal ions removal and the structure of EP was intensively studied in this study. The integration of Ep with polyaluminum chloride (PAC-Ep) coagulants exhibited higher coagulation performance than that of the polyaluminum chloride (PAC) because of the negatively charged NPs suspension and humic aid (HA) solution. Significant high removal efficiencies of dissolved organic matter (94.1%), turbidity (99.3%) and Zn ions (69.3%) were achieved by the PAC-Ep coagulants. The dual-coagulation properties of PAC-Ep for different pollutants was based on multiple mechanisms, including (i) Al³⁺ charge neutralization; (ii) hydroxy aluminum hydroxyl bridging formed polynuclearhydroxy complexes bridge and sweep colloidal particles; (iii) adsorption and bridging of Ep chain for the NPs and heavy metal ions. Results indicated that the destabilization of colloid was induced by the coexisting HA and higher removal was achieved as ions adsorption was enhance in the presence of HA complexation. On the basis of that, the extraction of polysaccharide is a promising candidate for its high coagulation performance in water treatment.