Synthesis and Characterization of Rice Husk Biochar and its Application in the Adsorption Studies of Lead and Copper

The present study aimed to use chemically activated rice husk biochar as an adsorbent for the removal of heavy metals from an aqueous solution. A series of the Rice husk biochar (RHB) samples were produced at different temperatures, as follows: 300, 400, 500, 600, and 700℃ for 2 hours each through pyrolysis process in Dalhan Scientific Muffle Furnace. The chemically treated rice husk biochar synthesized at 500℃ was used as potential char for removal of Cu(II) and Pb(II) from aqueous solutions. The sorption of these metal ions from an aqueous solution was determined after adsorption using Flame Atomic Absorption Spectrophotometry (AAS). The Shimadzu IR Affinity Fourier Transform Infra-Red Spectroscopy (FT-IR) was used for the characterization of rice husk char and it revealed the presence of OH, C=O, and COO- bonds which are responsible for heavy metal ions adsorption through chemisorption. The effect of adsorption parameters was determined that is; pyrolysis temperature which was found to be 500℃, the optimal contact time for the metal ions Cu (II) and Pb (II) was found to be 60 minutes, the optimum dosage was 0.250 g and optimum initial concentration was 2 mg/l. The kinetics were tested against pseudo-first order and pseudo-second order model as well Langmuir and Freundlich isotherms. Cu(II), adsorption process followed Pseudo-second order kinetics with regression coefficient (R2) 0.9942 and Langmuir isotherm model with R2 0.9895. For Pb(II), adsorption capacity followed Pseudo-second order kinetics with regression coefficient (R2) 0.99991 and Freundlich isotherm model with R2 0.96675 optimum equilibrium adsorption capacity of 0.5274 mg/g.