Preparation Of Biodegradable Polymer Composites And Its Performance In Heavy Metal Contaminated Soil

Heavy metals(HMs)have strong inhibitory effects on the growths and reproductions of animals and plants,and they are very easy to move in the soil-plant system,so they could cause serious adverse effects on human health and ecosystem.In-situ immobilization of HMs in contaminated soil is an effective and low-cost technology to reduce their mobility and bioavailability.In order to further develop environmentally friendly and cost-effective in-situ remediation technology,this paper studied the degradation and nutrient release performance of simple physical mixtures(PSRF+SAPWS)or semi-interpenetrating polymer network nanocomposites of PSRF and SAP(SI-PSRF/SAPWS)in heavy metal contaminated soil through tomato pot experiment,and further studied the effects of these composite materials on the physical and chemical properties,HMs bioavailability and mobility of contaminated soil In addition,a new kind of humic acid modified water absorption and water retention composite with semi interpenetrating network structure was prepared by interpenetrating PSRF,a linear polymer slow-release material containing nutrient elements,into the three-dimensional network of humic acid-g-poly(acrylic acid acrylamide).The main research content and results are as follows:(1)The degradation and nutrient release properties of simple physical mixtures(PSRF+SAPWS)or semi-interpenetrating polymer network nanocomposites of PSRF and SAP(SI-PSRF/SAPWS)in contaminated soil and non-contaminated soil were compared.The results showed that the degradation performance and cumulative release rate of nitrogen and carbon nutrients of the two polymer materials in polluted soil were lower than those of the corresponding non polluted soil treatment,while the cumulative release rate of phosphorus was higher than that of the corresponding non polluted soil treatment.In addition,SI-PSRF/SAPWS is better than PSRF+SAPWS in the degradation of polluted soil.(2)In the polluted soil,the application of PSRF+SAPWS,and SI-PSRF/SAPWS polymer materials increased soil nutrient content,improved soil microenvironment,and increased soil enzyme activity compared with no fertilization treatment.In addition,the substances released from the degradation of the two polymer materials participate in the synthesis and transformation of soil organic matter,thus adsorbing and fixing HM in the soil,reducing the content of active forms of heavy metals Cu,Zn,Cd and Pb in the soil and the content of heavy metals in the plant,improving the nutrient content of tomato plants in the polluted soil and tomato yield,especially in the treatment of SI-PSRF/SAPWS,tomato yield was highest,and it had the best inhibitory effect on heavy metal migration.(3)A new type of humic acid modified composite material with both water absorption and water retention and slow release of nutrients was prepared from PSRF molecular chain and HA-g-P(AA-co-AM)water-absorbing resin through solution polymerization and semi-interpenetrating network technology.FTIR and XRD were used to characterize the structure of the prepared composite,and the effect of the ratio of raw materials on the water absorption properties of the composite was studied.The slow-release behavior of the material and its effects on the water-holding and water-retaining properties of the soil were measured.The results show that the maximum water absorption rate of the prepared composite in tap water can reach 76.09 g / g.It can improve the water-holding and water-retaining properties of the soil after being applied into.In addition,it has excellent slow-release performances of nutrients nitrogen,phosphorus and potassium.After 30 days of cultivation in the soil,its cumulative release rates of nitrogen,phosphorus and potassium are 31.81%,47.71% and 79.30%,respectively.The prepared composite can be used as a high-quality water and fertilizer material in agricultural applications.