SUSTAINABLE RE-UTILISATION OF WASTE MATERIALS AS ADSORBENTS FOR WATER TREATMENT

Abstract

Organic compounds present in polluted wastewater exhibit stability during treatment. Methylene blue, an organic pollutant known for its hazardous oxidative properties, is of particular concern as it is commonly found in the effluent from the textile industry, and its presence in the environment threatens the biosphere. Given the stability of methylene blue dye, sorption via biochar materials emerges as a viable pathway for remediation. Biochar, derived from waste materials such as straw flax and sewage sludge through pyrolysis, is an effective medium. This approach addresses waste management concerns and aligns with the principles of circular economy and environmentally friendly practices. The scope of this work is to study the adsorption properties of biochar from sewage sludge or straw flax in removing methylene blue from water. The working concentration of methylene blue (MB) in water was 20 ppm. Biochar was characterised by various techniques such as Scanning Electron Microscopy, Thermogravimetric Analysis, Fourier Transform Infrared Spectroscopy, and X-ray Diffraction. The biochar efficiency as an adsorbent was proved by the MB removal of 77.33% achieved after 30 min for 220 mg of straw flax-derived biochar with particle size in the 100-400 μm range. Using the sewage sludge-derived biochar (220 mg, 100 μm < d < 400 μm), an MB removal of 30.86% was achieved after 30 min. The straw flax biochar (100 μm < d < 400 μm) showed the lowest thermal tolerance, as 65.71% of it retained its weight at 800 oC in the N2 environment. Biochar with particle size distribution ranging in 100-400 μm was more effective than particle sizes in 400-800 μm. The maximum adsorption efficiency observed was 84.37%, and it was achieved by 220 mg of the straw flax biochar with particle size in the range of 100-400 µm after 2 hours. The significance of this investigation lies in its innovative approach to repurposing waste materials generated from pyrolysis for the treatment of water contaminated with the organic dye methylene blue, aligning with the principles of the circular economy.