Response Surface Modelling and Optimization of Lead Adsorption from Wastewater Using Rice Husk Activated Carbon

Abstract

Nigeria is renowned for its vast production of paddy rice, resulting in a significant volume of rice husk generation. Consequently, the conversion of these quantities of rice husk into beneficial applications is imperative to mitigate environmental pollution. The rice husk, procured from local millers in Zaria market, Nigeria, was subjected to thermal and chemical methods to produce activated carbon. The carbonization process involved heating at three different temperatures (300, 350 and 400 ℃) and subsequent mixing with 1M H3PO4 at a 1:2 ratio. Batch adsorption experiments were conducted, varying dosages of rice husk activated carbon (1 - 5 g), lead initial concentrations (10 - 60 mg/l), and carbonization temperatures (300 - 400 ℃). The Response Surface Methodology was utilized to model the adsorption capacities and removal efficiencies obtained. At carbonization temperature of 350 ℃, initial lead concentration of 60 mg/l, and adsorbent dosage of 3 g, the optimum removal efficiency and adsorption capacity 100% and 1.690 mg/g, respectively were observed. The veracity of the model equations was confirmed through the verification of the optimum adsorption conditions, with recorded percentage errors of 0.253% and 17.988%, for removal efficiency and adsorption capacity, respectively. The study's findings showed that rice husk activated carbon was highly effective in removing lead from wastewater. Furthermore, the model equations demonstrated reliability in forecasting the responses, and the optimum conditions were deemed valid.