Removal of Microplastics from Water by Using Agro-Waste Biochar

Microplastics (MP), an emerging contaminant, have attracted attention all over the world for their increased pollution in the air, water, and soil biota, which in the long run causes ecotoxicological effects as well. Water and Wastewater treatment plants have treatment processes like rapid sand filters, disc filters, and membrane filtration, which remove more than 90% of the MPs; still, some of them get left over in the final effluent. Although each method has benefits and drawbacks of its own, the main disadvantage is changing of membranes from time to time, the use of chemicals, the generation of toxic by-products, high cost and insufficient removal of contaminants. In recent times, adsorption has emerged as a phenomenon which is characterized by its cost-effective nature, low operation costs, high removal efficiency, eco-friendly and extensive processing range. One such adsorbent is biochar (BC), which is a porous carbon substance prepared from various biomass feedstocks like wood, shells, sludge, forest residue etc. by the process of pyrolysis. In this study, rice straws biochar is synthesized at three different temperatures of 300, 450, and 600 °C in a muffle furnace for a residence time of 1 h. The synthesized biochars were applied for the removal of Microplastics from water sample. The removal efficiency at the three temperatures was found to be 75, 81 and 90%, respectively. According to the study, the process of adsorption is driven by electrostatic attraction and chemical bonds between MP and biochar. The degree of carbonization gets affected by an increase in the pyrolytic temperature, thus improving the structural, elemental, morphological and sorption properties. The study emphasizes the important role of rice straws adsorption in microplastic removal. Composite biochar materials are crucial for improving microplastic removal and immobilization.