ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Preparation of iron-modified biochar from rice straw and its application for the removal of lead (Pb⁺²) from lead-contaminated water by adsorption

Mushtaq Ahmad, Izaz Ul Islam, Maqbool Ahmad, Shah Rukh, and Ihsan Ullah

Department of Chemistry Govt. Post Graduate College Mardan, Higher Education Department, Peshawar, Pakistan

E-mail: ihsan.chem@tju.edu.cn

Received: 24 October 2021  Accepted: 31 January 2022

Abstract:

Lead pollution is a major cause of increasing blood and cardiac diseases. Adsorption is a good method for the treatment of polluted water. In this project, we prepared biochar from rice straw by pyrolysis at 600 °C in a thermolyne 1400 furnace. The Biochar was modified with iron by adding the aqueous solution of FeCl₃/FeSO₄ to the suspension of biochar in an aqueous solvent followed by raising the pH to 11. The unmodified and iron-modified biochar (FMBC) were characterized by furrier transform infrared spectrometer, energy dispersive X-ray spectrometer, X-rays diffraction spectrometer, point of zero charge (pH_PZC), transmission electron microscope, and scanning electron microscope. Batch mode was used to study the adsorption potential of FMBC for lead. Different conditions were applied to the adsorption process to study the influence of pH, initial concentrations, contact time and to set optimum conditions for maximum adsorption of Pb⁺². The maximum adsorption capacity (q_e) of 52.8 mg/g of lead onto iron-modified biochar (FMBC) was obtained at a contact time of 240 min, pH 5, and adsorbent dosage of 0.05 g/80 ml for 35 mg⁻¹ of lead solution. Experimental isotherm data were investigated theoretically using Temkin's Freundlich, and Langmuir adsorption isotherm model, while kinetic data were investigated using pseudo-second order (PSO) and pseudo-first order kinetic models. The equilibrium adsorption isotherm modeling and kinetic studies show that obtained data were compatible with Langmuir, and PSO kinetic model, which reveals that the nature of the adsorption is chemisorption. The adsorption capacity (q_e) of FMBC for the lead was higher (q_e = 60 mg/g) than the adsorption capacity of other adsorbents previously investigated. FMBC was paramagnetic, which allow its convenient magnetic isolation from the solution after the adsorption process. The higher adsorption capacity and possible magnetic separation of FMBC from aqueous solution suggest that FMBC has the potential to be practically applied for the treatment of lead (II) polluted water.

Keywords: Rice straw; Pyrolysis; Raw biochar (RBC); Iron-modified biochar (FMBC); Lead; Adsorption; Adsorption capacity (q e)

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-022-02118-y

Chemical Papers 76 (6) 3789–3808 (2022)