Study on the adsorption of Cd(II) in aqueous solution onto biochar materials synthesized from rice husk via microwave-assisted pyrolysis method

Biochar materials from rice husk were successfully synthesized using the microwave-assisted pyrolysis (MAP) method, and subsequently applied for the adsorption of Cd(II) ions in aqueous solution. The characteristics of the materials were analyzed using different methods. The factors influencing the adsorption process were investigated, including pH, time, concentration, and temperature. 03 isotherm models composed of: Langmuir, Freundlich, Sips models were utilized to study the isotherm properties of the adsorption process. The results demonstrate that the biochar material synthesized via the MAP method exhibits high porosity (surface area = 270 m2/g, with an average pore size of approximately 5.1 nm). This material is capable of adsorbing Cd(II) ions from aqueous solutions optimally at pH 5.0, with an adsorption equilibrium time of 180 mins. The maximum adsorption capacity calculated from the Langmuir model at 307 K is 6.22 mg/g.