Preparation of novel biodegradable starch/poly(vinyl alcohol)/bentonite grafted polymeric films for fertilizer encapsulation

Sufficient hydroxyl moiety, ease of accessibility, biodegradability and reaction compatibility with other molecules make starch a basic ingredient for polymeric synthesis and to prepare encapsulated controlled release fertilizers. This article aims to prepare biodegradable clay-polymeric (starch/PVA) blended encapsulating films (CPSBs) from starch/PVA and economically feasible clay-fractioned bentonite for CPSB-encapsulated diammonium phosphate (DAP) production. The XRD, TEM and FTIR spectroscopy recognized the compatibility of bentonite with starch/PVA blend; several micropores in CPSB surface was visible through SEM. Relative crystallinity index, density of CPSBs increased with increasing bentonite content (0-20 wt%); but, porosity, water absorption was decreased. Half-life of CPSB-10 was 37.4, 40.1 and 51.9 days with Aspergillus awamori, Trichoderma viride and uninoculated soil, respectively. Nitrogen (N) and phosphorus (P) release data from CPSB-encapsulated-DAP and uncoated DAP fitted well to Korsmeyer-Peppas model. Overall, greater bentonite content stabilizes the CPSB structure and CPSB-encapsulation reduced the N and P release from DAP.

Automated summary

This study focused on preparing biodegradable clay-polymeric blended encapsulating films using starch/PVA and fractioned bentonite, for the production of encapsulated diammonium phosphate (DAP). The results showed that higher bentonite content can stabilize the structure of the encapsulating films and reduce the release of nitrogen and phosphorus from the encapsulated DAP.