| Vinyl polymer has been extensively used in papermaking, leather making, textile printing and dyeing, oilfields, cosmetics etc. Vinyl polymer/nano-ZnO could combine the properties of the individual constituents such as mechanical, flexibility, optical, electrical properties, and broaden its application range. As a new class leather finishing agent, polymer based nanocomposites brings a new vitality into leather making. With the rapid development of nanomaterials, the risks of nanomaterials have attracted a great deal of attention in recent years. The underused leather agent firstly discharged into wastewater treatment system. Hence, the transformation and biological effects of polymer based nanocomposites under the conditions of biological treatment is significant in evaluation of its environmental risks, while very few related studies are available.In this research, the adsorptive, biodegradability, bacterial community success and diversity, luminous bacteria and dehydrogenase concentration of vinyl polymer and its nano-ZnO composite were studied. Vinyl polymer/nano-ZnO including polydiallyl dimethyl ammonium chloride-acrylic-acrylamide-hydroxyethyl acrylate/nano-ZnO(PDM/ZnO), polyacrylate/nano-ZnO(PA/ZnO), and polyer matrix including polyacrylate (PA), PDM polymers which was synthesized using polydiallyl dimethyl ammonium (PDM), acrylic acid (AA), acrylamide (AM) and 2-hydroxyethyl acrylate (HEA). The difference of the transformation and biological effect of vinyl polymer and its nanocomposit were also compared. The main results of this study include the following parts:(1) Adsorption studies were carried out on vinyl polymer and its nano-ZnO composite by activated sludge. The adsorption rate is quickly and adsorption equilibrium can be achieved within 30 min for all materials. The adsorption amount of PDM, PDM-AA, PDM-AA-AM, PDM-AA-AM-HEA, PDM/ZnO-B (blending method), PDM/ZnO-S(sol-gel method), PA and PA/ZnO were 279 mg/g,452 mg/g,481 mg/g,409 mg/g,448 mg/g,285 mg/g,484 mg/g, and 356 mg/g, respectively. The adsorption capacity of the activated sludge for PDM was the lowest among the 8 materials. The cationic quaternary ammonium salt of PDM is adsorbed by activated sludge via electrostatic interaction. Because of the different hydrophobicity and electric charge, the adsorption capacity of the amphoteric polymers of PDM-AA, PDM-AA-AM and PDM-AA-AM-HEA are differences. Distribution is major role in PDM-AA-AM and PDM-AA-AM-HEA adsorption. Distribution and electrostatic interaction may play major roles in PDM-AA adsorption. PDM/ZnO production method affects its surface electric charge thereby showed diffrence adsorption amount. The adsorption amount of PDM/ZnO-B was higher than its polymer matrix (PDM-AA-AM-HEA), while the adsorption amount of PDM/ZnO-S was lower than its polymer matrix. The adsorption capacity of the activated sludge for PA/ZnO was higher than the rest tested materials. The introduction of nano ZnO to PA reduced its adsorption capacity. Distribution is the major role in PA and PA/ZnO adsorption.EPS-extracted activated sludge and inactivated sludge decreased the surface area and negative charge of the sludge, which leading to a decrease adsorption capacity for all the tested samples. The presence of Cr3+ ions improved the tested materials adsorption except PA and PDM. The presence of Cr3+ ions slightly improved the six materials adsorption probably because Cr3+ may directly combine with carboxyl or hydroxyl group. Coexisting Ca2+ and Na+ ions have negligible effect on all the tested composites adsorption capacity. This probably because the cations in solution may neutralize the negative charge carried by the activated sludge flocs. Meanwhile, the existed competitive effects might make the active sites fewer. Moreover, Ca2+ and Na+ addition lead to lower viscosity values and higher compressibility of activated sludge.(2) After 1 day aerobic treatment, the concentrations of all the tested samples were increased, suggesting that the samples were desorped from the activated sludge. After 1 to 2 days incubations, biodegradation proceeded gradually. The COD, TOC, BOD, CO2 results showed that vinyl polymers and its nano-ZnO composites exhibited certain biodegradability in the activated sludge reactor. PDM polymers and its nano-ZnO composites seemed to be unbiodegradable in anaerobic system. PA and PA/ZnO showed good adsorption-biodegradation ability. The removal efficiency of vinyl polymers and its nano-ZnO were relatively higher in aerobic system than in anaerobic system. The results showed that the introduction of nano ZnO to vinyl polymer enhanced the biodegradability. The acylamino, acid group and ester group are easily biodegraded group.(3) In the aerobic system, the inhibition of PDM-AA-AM-HEA to dehydrogenase activity was lower than PDM, while higher than PDM/ZnO, suggesting that the inhibition to dehydrogenase activity decreased when the introduction of AA、AM、HE A to PDM, and the inhibition to dehydrogenase activity further decreased when the the introduction of nano-ZnO to PDM-AA-AM-HEA. Nitrospirae decreased under continuous exposure to PDM, PDM-AA-AM-HEA, PDM/ZnO-S and PDM/ZnO-B. Firmicutes generated under continuous exposure to PDM and PDM-AA-AM-HEA. The results showed that the introduction of nano-ZnO to PDM-AA-AM-HEA decreased the biological effect. The biological effect of PDM/ZnO relate to the preparation method. The effect of the PDM/ZnO to the microorganisms which made by sol-gel polymerization production method (PDM/ZnO-S) was lower than that made by blending polymerization (PDM/ZnO-B). PA and PA/ZnO were little effect to microorganisms. The luminous bacteria inhibiting ratio were asistant with the above results.In summary, this study provided evidence that adsorption can aggregate vinyl polymers and its nano-ZnO composites. Chemical composition and molecular structure, hydrophobicity, and surface charge characteristics impact the behavior of vinyl polymers and its nano-ZnO removal from water. The introduction of nano ZnO to vinyl polymer enhanced the biodegradability and decreased the toxicity effect. The adsorption-biodegradation can be employed for an effective solution for nano-ZnO composites and its vinyl polymer matrix removal in wastewater treatment activated sludge. The results suggesting that the bacterial community analysis and dehydrogenase concentration activity determination could be used to evaluate the biological effects of vinyl polymer nano-ZnO composites in activated sludge. |
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