IRON IMPREGNATED RICE HUSK ASH ADSORBENT FOR CYANIDE REMOVAL FROM CASSAVA PROCESSING EFLLUENT
Rice husk (RH) was calcined and the resultant ash (RHA) was impregnated with Fe, (Fe-RHA). Both were used to adsorb cyanide from simulated cyanide solution and effluent from cassava processing. X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), and Scanning Electron Microscope (SEM) were used to characterize the RH, RHA and Fe-RHA, while UV spectrophotometer was used to monitor the cyanide concentrations. BET results for surface area, pore volume and pore width are 552 m2/g, 0.625 cm3/g, and 3.17 nm, respectively for RHA while those for Fe-RHA are 475.6 m2/g, 0.2253 cm3/g, and 2.128 nm respectively. The optimum conditions for the synthesis of Fe-RHA when response surface methodology was employed were 0.075 mol/L, 630 oC, and 11minutes respectively for impregnation ratio, calcination temperature, and calcination time. Batch adsorption processes for cyanide removal were carried out by contacting RHA and Fe-RHA adsorbents with effluents A (juice extracted from cassava tubers), B (effluent from cassava processing plant), and C (effluent from cassava processing plant after sedimentation). The adsorption efficiencies when RHA adsorbent was used were: 45.10%., 40.09% and 58.18% respectively for effluents A, B, and C. Similarly, 64.71%, 60.37%, and 63.03% respectively when Fe-RHA adsorbent was used. The analysis of the adsorption data using the Langmuir and Freundlich models showed that Langmuir model is suitable with adsorption capacity of 4.2 mg/g with a correlation coefficient (R2) of 0.9924. Pseudo-second-order kinetic model has been found most applicable when first, second, and intra-particle kinetic models were used to fit the data.