Adsorption Removal Of Persistent Organic Ollutants From Dyeine Wastewater By Bentonite/Surfactant In One-step Process

Persistent Organic Pollutants (POPs) widely exist in dyeing wastewater. If not effectively treated, they would cause serious harms to human beings and environments. Therefore, it is essential to study and control the POPs pollution in dyeing wastewater. Here, a method of POPs enrichment and analysis from dyeing wastewater was established by using liquid-liquid extraction, solid phase extraction, HPLC and GC/MS technologies. A bentonite/surfactant one-step process was proposed to replace the traditional PAC flocculation process in order to improve the removal efficiencies of POPs in dyeing wastewater. In this thesis, the removal of representative POPs in the one-step process was evaluated and their removal mechanism was also discussed. Additionally, the adsorbed organobentonite sludge was regenerated by theomo processing. The main valuable findings were as follows:(1) A method of POPs enrichment and analysis from dyeing wastewater was established, and four categories of POPs species were detected, including six POPs-like dyes (disperse orange30, disperse orange62, disperse red43, vat purple1, reactive blue13and acid yellow72), pentachlorophenol, PAHs and PCBs in the range of50-95mg/L,15-50μg/L,800-1200ng/L and7-20ng/L, respectively. Disperse POPs-like dyes were the main type of dyes, accounting for more than85%. The low molecular weight PAHs and PCB-11were the major PAHs and PCBs species, and mainly adsorbed on particulates or sludges.(2) Bentonite/surfactant one-step process was applied in the treatment of dyeing wastewater. Comparing with the traditional PAC flocculation process, the removal of representative POPs increased significantly, which were93.6%,98.7%,90.4%and61.4%for POPs-like dyes, pentachlorophenol, PAHs and PCBs, respectively. Meanwhile, biological biodegradability (B/C) increased from0.24to0.48in the effluent, which provide an effective guarantee for the stable operation of the subsequent biological treatment process and the safe discharge of wastewater.(3) The main removal mechanism of representative POPs in dyeing wastewater by bentonite/surfactant one-step process was investigated in detail. In the bentonite/surfactant one-step process, raw bentonite can adsorb organic cations by ion exchange, and then assemble the organobentonite automatically. In the one-step process, the removal of anionic POPs from wastewater was mainly controlled by chemical adsorption, and the adsorption of nonionic POPs complied with linear sorption model, which was mainly controlled by partition. The interaction between surfactant and POPs could promote the adsorption of POPs onto the self-assembled organobentonite. Meanwhile, polar or weekly polar organic compounds could promote the adsorption of nonpolar POPs. Self-assembled organobentonite can efficiently adsorb the non-polar POPs in dyeing wastewater.(4) Organobentonite sludge sorbing POPs was regenerated by thermo processing. The best regeneration temperature was450℃and the best time was1.5h. After several times of repeated adsorption and regeneration, the adsorption capacity of the regenerated sample for aniline was nearly six times to raw bentonite. It could be considered as an effective way to solve the secondary pollution of sludges.