Response Surface Methodolgy (RSM) Optimization and Characterization of Silica Production from Bida Rice Husk

Abstract

Due to the fact that the compositions of silica derived from rice husk depends on the soil type and composition, type of fertilizer and chemicals used during planting and climate or geographical factors. In this particular research, the production of silica from rice husk obtained from Bida was optimized using Response Surface Methodology (RSM). The final silica produced at optimum conditions was characterized using XRF, XRD, SEM/EDX and BET, Preliminary investigations were conducted on the reaction variables which include: NaOH concentration, volume of NaOH, reaction temperature and reaction time. The results obtained were used to generate a design matrix using design expert 13.0 software via Box-Behnken Design (BBD). The software suggested a quadratic model that predicted the optimum yield of 7.655 g at optimum conditions of 3.0 M NaOH, 250 ml NaOH, 90 minutes reaction time and 100 °C reaction temperatures. The model fit statistics also shows that the predicted Rº value of 0.9141 is in agreement with the adjusted Rª value of 0,9654. The adequate precision of the model is 28.558 with an insignificant lack of fit. P. value of 1.71. The experimental optimum yield recorded is 7.30 g with a standard deviation of 0.251. The XRF analysis reveals 71.415 % and 79.120 % silica in the rice husk and final silica respectively. The XRD results shows predominance of amorphous silica while the SEM image shows that the silica possesses agglomerates particles of irregular shapes that are jagged and porous. The elemental analysis from the EDX is in accord with the XRF result. The BET results showed that the silica has a surface area of 314 m%/g pore volume of 0.1761 cm'/g and pore size of 2.128 mm. From all the results gathered, silica of significant quality and characteristic can be successfully produced from Bida rice husk.