Incorporation of biochar into semi-interpenetrating polymer networks through graft co-polymerization for the synthesis of new slow-release fertilizers

Modern agriculture is strongly calling for the development of environment-friendly slow-release fertilizers (SRFs) with high water retention. In this study, a new biochar embedded-Semi-IPN based SRF is developed by the incorporation of biochar into semi-interpenetrating polymer networks (Semi-IPN) via grafted co-polymerization, which holds great potential to combine the advantages of biochar and Semi-IPN when they are used in SRFs. The results show that the as-prepared biochar embedded-Semi-IPN based SRF (BiBe-SRF) exhibits a high water-retention capacity with the value of 73.50% after 25 days, which far outstrips that of Semi-IPN based SRF without the incorporation of biochar. BiBe-SRF also has a better slow-release performance of nutrients than the Semi-IPN based SRF. The release ratios of N, P and K from Semi-IPN based SRF within 30 days reach in the range of 95.5%-100.0%, but they are less than 80.0% for BiBe-SRF. The degradation ratio for BiBe-SRF is 62.63% after 90 days' degradation experiment which is higher than Semi-IPN based SRF, suggesting that the presence of biochar significantly improves the degradability of BiBe-SRF. Pot experiments reveal that pepper seedlings fertilized by BiBe-SRF grow better than those fertilized by Semi-IPN based SRFs, which further highlights its great potentials for the practical application. The mechanism study suggests that the existence of biochar is beneficial for the formation of improved porous structure and generation of abundant cross-linking points within BiBe-SRF, and it is also responsible for the high hydrophilicity of BiBe-SRF. Overall, this study demonstrates a new route for the development of environment-friendly SRFs with high water retention. (C) 2020 Elsevier Ltd. All rights reserved.