Study on adsorption performance and mechanism of peanut hull-derived magnetic biochar for removal of malachite green from water

Abstract

Magnetic biochar (MBC) has the advantages including wide source of raw materials and low cost, and has become a potential adsorbent for water treatment, overcoming the shortcomings of biochar (BC) with the hard separation of solid and liquid. Peanut hull-derived magnetic biochar loaded with Fe _3 O _4 (Fe _3 O _4 /BC) was prepared by co-precipitation method. By means of material characterization and batch processing experiments, material properties and environmental factors affecting adsorption performance were investigated. The adsorption mechanism of Fe _3 O _4 /BC on malachite green (MG) was revealed using adsorption isotherms, adsorption kinetics and thermodynamics. The results showed that Fe _3 O _4 particles were uniformly loaded, the total pore volume was increased, surface oxygen-containing functional groups were formed, and the maximum adsorption capacity of the biochar reached 175.4 mg g ^−1 , 1.6 times of that before modification. In a wide PH range, Fe _3 O _4 /BC showed high adsorption performance for MG, and significant influence from ionic strength wasn’t found. Chemical adsorption was the main adsorption mechanism, including electrostatic interaction, cation exchange, hydrogen bonding and π - π interaction. The study of adsorption mechanism will promote the application of MBC in the removal of organic pollutants from water.

Keywords

• peanut hull
• magnetic biochar
• co-precipitation
• malachite green
• adsorption mechanism