Influence of Pyrolysis Parameters Using Microwave toward Structural Properties of ZnO/CNS Intermediate and Application of ZnCr2O4/CNS Final Product for Dark Degradation of Pesticide in Wet Paddy Soil.

Pesticide is a pollution problem in agriculture. The usage of ZnCr₂O₄/CNS and H₂O₂ as additive in liquid fertilizer has potency for catalytic pesticide degradation. Colloid condition is needed for easy spraying. Rice husk and sawdust were used as carbon precursor and ZnCl₂ as activator. The biomass-ZnCl₂ mixtures were pyrolyzed using microwave (400-800 W, 50 min). The products were dispersed in water by blending then evaporated to obtain ZnO/CNS. The composites were reacted with KOH, CrCl₃·6H₂O, more ZnCl₂, and little water by microwave (600 W, 5 min). The ZnCr₂O₄/CNS and H₂O₂ were used for degradation of buthylphenylmethyl carbamate (BPMC) in wet deactivated paddy soil. TOC was measured using TOC meter. The FTIR spectra of the ZnO/CNS composites indicated the completed carbonization except at 800 W without ZnCl₂. The X-ray diffractograms of the composites confirmed ZnO/CNS structure. SEM images showed irregular particle shapes for using both biomass. ZnCr₂O₄/CNS structure was confirmed by XRD as the final product with crystallite size of 74.99 nm. The sawdust produced more stable colloids of CNS and ZnO/CNS composite than the rice husk. The pyrolysis without ZnCl₂ formed more stable colloid than with ZnCl₂. The ZnCr₂O₄/CNS from sawdust gave better dark catalytic degradation of BPMC than from rice husk, i.e., 2.5 and 1.6 times larger for 400 and 800 W pyrolysis, respectively. [ABSTRACT FROM AUTHOR]