Optimization of Lead Ion Adsorption Capacity by Biomass Mixture of Palm Bunches and Rice Husks after Activated with Citric Acid

Optimization of lead ion adsorption rate by biomass mixture of palm bunches and rice husks (PB-RS) after activated with citric acid was carried out with the Design-Expert 6.0.8 software. The purpose of this study was to obtain an optimal response (adsorption rate) which was influenced by several dependent variables (biomass weight ratio, activator concentration, and contact time). Biomass mixture was carbonized in the tube furnace at 500 °C for 2 hours followed chemically activated using citric acid as an activator. The activated carbon formed was contacted with water containing Pb(II) ion. Pb removal rate was measured to observe the biomass performance on Pb(II) ion absorption with various variables including biomass ratio, citric acid concentration, and contact time. Pb(II) ion concentration was analyzed using Atomic Absorption Spectrophotometry, Shimadzu AA-6300 while the optimum adsorption of Pb ion was analyzed using Design Expert 6.0.8 software with Central Composite Design (CCD). The results showed that the variable of mass ratio, activator concentration, and contact time influence the rate of Pb(II) ion adsorption from the water phase. Base on the optimization analysis, the optimum condition of Pb(II) ion adsorption achieved at 30 g of activated PB-RS biomass, activator concentration (citric acid) of 0.6 mol/L, at 99.88 minutes contact time, and at a Pb(II) initial concentration of 99.42 mg/L. In this optimum condition, Pb(II) ion adsorption capacity obtained was 3.01 mg/g.