Biochar versus Iron Oxide-biochar Performance as Adsorbents for Lead and Methyl Orange from an Aqueous Solution

Abstract

Water purification is slowly becoming a problem worldwide due to population growth. Lack of proper wastewater disposal from domestic and industrial sources has escalated water pollution in developing countries. Continuous pollution of water sources has made water purification for domestic supplies very expensive. Modern and cost-effective ways of water purification are urgently needed. One of the modern emerging technologies is adsorption using nano-materials. The aim of the study was to prepare an engineered iron oxide-biochar (Fe2O3-BC), a nano-composite using pyrolysis and microwave activation. The efficiency of the nano-composite was evaluated in the removal of the heavy metal lead (Pb) and the dye methyl orange (MO) in aqueous solutions. Infrared spectroscopy was used to identify the functional groups present in the synthesized biochars before and after adsorption. The adsorption properties of the synthesised Fe2O3-BC and biochar (BC) were determined by application in lead metal and methyl orange aqueous solutions on known concentrations. FAAS and UV/VIS Spectrophotometry were used for Lead and Methyl Orange concentrations measurements respectively. Batch adsorption experiments were conducted to investigate the capacity of Fe2O3-BC and BC to remove MO and Pb in aqueous solutions.  A dose of 50 mg Fe2O3-BC had the highest percentage MO removal of 89.81% at pH 2 while 50 mg of BC had a highest of 11.55% at pH 12. A dosage of 100 mg of Fe2O3-BC had 100% MO removal and 250 mg BC achieved a maximum of 30.61% removal in 30 minutes. Maximum MO removal concentrations were 70 mg/L and 55 mg/L respectively for Fe2O3-BC and BC adsorbents. Both Fe2O3-BC and BC had Pb2+ removal of 97% in 30 minutes. A dose of 65 mg for both Fe2O3-BC and BC adsorbents had 100% removal of Pb2+. The adsorption studies of both MO dye and Pb2+ on Fe2O3-BC nano-composite fit the Langmuir isotherm (R2 value of 0.999) and Temkin isotherm (R2 value of 0.919). The Fe2O3-BC nano-composite adsorbs Pb and MO dye better than biochar. The Fe2O3-BC nano-composite could be a good adsorbent for other cations and anions. More work need to be done in order to investigate the adsorption potential of other cations and anions using Fe2O3-BC nano-composite.