Valorization of almond shells’ lignocellulosic microparticles for controlled release urea production: interactive effect of process parameters on longevity and kinetics of nutrient release

In this study, almond shell lignocellulosic bio-waste material is utilized as a spray suspension for the production of controlled release urea in a rotary pan coater. For this purpose, the almond shell particles are chemically modified to enhance the spray characteristics and mechanical properties of the coating film. Response surface methodology is employed to investigate the interactive effect of process parameters on time and kinetics of urea release from controlled release product. The FTIR spectrum of the coating suspension vindicates the acetylation of the lignocellulosic particles of almond shells. TGA reveals an enhancement of thermal stability of the chemically modified almond shell particles. The viscosity of spray suspension decreases with increase in temperature and increases with increase in the particle size of the spray suspension. The release experiments indicate that complete urea dissolution took place in a couple of minutes, whereas it took more than 20 h for the 100% release of urea from coated product. The analysis of variance reveals that spray rate is the most influential process parameter among the other studied parameters.