Adsorption Of Heavy Metals And Corresponding Nanoparticles With The EPS In Typical Sludges

With the rapid development of technology and urban social modernization, extensive use of heavy metals and nanoparticles inevitably lead to serious environmental problems. Currently, wastewater containing heavy metals and sewage containing nanoparticles were mainly treated by biotechnology. Sludge was a major component of biological wastewater treatment system. The settling properties, dehydration performance, bioflocculation and surface characteristics of sludge were affected largely by the sludge extracellular polymeric substances(EPS). At present, the adsorption characteristics of heavy metal ions and nanoparticles by the whole sludge EPS are widely studied, while the component analysis of EPS which affects the adsorption performance is unknown, and most of the studies are focused on waste activated sludge. Therefore, a comprehensive inquiry of sludge EPS is important for heavy metal ions and nanoparticles removal by absorption.The hydrophilic/hydrophobic components and the physical and chemical characteristics of three kinds of EPS(the EPS fom activated sludge, anaerobic granular sludge and anaerobic granular sludge) were studied by classification experiments.The results showed that aromatic substances and microbial metabolites were the main contents in all the three kinds of sludge. The content of protein in anaerobic flocculent sludge was the highest, which was followed by anaerobic granular sludge and activated sludge; As for polysaccharides, TOC and UV-254 value, anaerobic flocculent sludge contained the highest, followed by activated sludge and anaerobic granular sludge. sedimentation properties of the sludge were positively correlated with the content of the hydrophilic fraction, and so did the relationship betweent dewatering performance and the content of hydrophobic substance.The components of EPS and its adsorption properties of Zn2+、Ti4+、Cu2+and their nanoparticles by three kinds of sludge were performed in this study. The results showed that: for the same kind of metal ion, the anaerobic granular sludge showed the highest adsorption capacity, while anaerobic flocculent sludge and waste activated sludge were similar; for the same kind of nanoparticles, the highest adsorption capacity was got by activated sludge, followed by anaerobic flocculent sludge and anaerobic granular sludge; for the same sludge EPS, its affinity for heavy metal ions was Cu2+> Ti4+> Zn2+ and for the nanoparticles is Ti O2> Cu O>Zn O.The thermodynamics and kinetics were studied through the adsorption isotherms and kinetic equations of Zn2+, Ti4+, Cu2+and their nanoparticles by anaerobic granular sludge. The results showed that: analog Freundlich isotherm equation could fitted the adsorption of Ti4+, Cu2+ and nano-Cu O by EPS perfectly, while Langmuir isotherm equation modeling was suitable for Zn2+, nano-Zn O and nano-Ti O2. In addition, Cu2+, Zn2+, Ti4+ and their nanoparticles are suitable for simulation with the pseudo-secondorder kinetic model, and the adsorption are mainly chemical adsorption process.Infrared spectroscopy and scanning electron microscopy were adopted to find the adsorption mechanism of Zn2+, Ti4+ and Cu2+ and their nanoparticles through different kinds of sludge EPS. The results showed that sludge EPS combined with Zn2+, Ti4+, Cu2+ and their nanoparticles through the function of hydroxyl, carboxyl, amino, amide groups and C-O-C groups.