ADSORPTION OF COPPER IONS ONTO RICE HUSK ACTIVATED CARBON PREPARED USING ULTRASOUND ASSISTANCE: OPTIMIZATION BASED ON STEP-BY-STEP SINGLE VARIABLE KNOCKOUT TECHNIQUE

This study proposed 3 types of rice husk activated carbon prepared by a variation of chemical activation techniques includes non-stirred, mechanical stirred and mechanical stirred with ultrasound assistance. FTIR transmission spectra showed that aromatic rings and alkenes were released more on husk activated carbon with ultrasound assistance in chemical activation (RH-ACMUS), and SEM images confirmed that more pores were obtained in RH-ACMUS. The effect of independent variables on adsorption capacity of Cu(II) ions was investigated. An optimum condition of batch mode adsorption was obtained based on step-by-step single variable knockout technique, which consisted of 500.09 mg/L of Cu(II) ions in 100 mL of aqueous volume, 1 g of RH-ACMUS, at 100-rpm magnetic stirring, pH 6, 1 atm and 27 degrees C. The adsorption capacity in the optimum condition was 39.84 mg/g. Adsorption of Cu(II) ions onto RH-ACMUS fitted very well (R-2 = 0.99) with pseudo-second order kinetic, and the adsorption rate and equilibrium capacity determined were 0.88 g/mg.min and 39.84 mg/g, respectively. In addition, it was best fit (R-2 = 0.91) to Freundlich adsorption isotherm with porous volume obtained was 1.52 L/mg, and adsorption intensity was 1.46, and it indicated physical adsorption was taking place dominantly.