Plenary, Clean Water and Sanitation (SDG 6), Climate Action (SDG 13)
Biochar-based water treatment: a sustainable technology for clean water in developing countries Dinesh Mohan Professor, School of Environmental Sciences, Jawaharlal Nehru University, New Delhi , India Climate change, environmental contamination, land degradation, food and water shortages lead to social, economic, and environmental damage. These threats should be addressed to stop major disasters happening now and in near future. The rise in anthropogenic and geogenic water pollution, high living standards and human population growth vaults water security to a high global priority. Thus, the need for sustainable technologies for clean drinking water continues to increase. Sustainable Development Goal (SDG) 6 addresses the need for “clean water and sanitation for all”. This is one of 17 SDGs established by the United Nations (UN) General Assembly in 2015. Its official wording is: “Ensure availability and sustainable management of water and sanitation for all”. This must be on the top priority of Commonwealth chemists to achieve UN SDGs by developing sustainable technologies for clean water. It requires action on many fronts including harnessing and maximizing the potential of sustainable technological innovation. Water pollutants span a huge contaminant range. Contaminants pose serious health issues. Environmental regulations set up by many agencies require that many of these pollutants must be remediated before water is consumed. Sorption, precipitation, coagulation, filtration, and ion exchange are most used for water cleanup. Sorption is widely used due to its low operational costs. Sustainable Biochar (BC) from biomass and wastes is an excellent option for climate change mitigation coupled with soil fertility management, contaminated soil remediation, carbon sequestration in soils and agricultural by-product/waste recycling. Various feeds and reactors (slow and fast pyrolysis) can be used to prepare biochars. We have developed a variety of biochars by slow and fast pyrolyses of agricultural wastes/byproducts including pine needles, water hyacinths, sugarcane bagasse, rice husks, wheat husks, corn cobs, corn stover, banana peels, tea residues, and okra stems. Modified biochars with enhanced sorption capacities including magnetic biochars nano-sized particulate biochar, zero-valent iron-decorated biochar, BC- iron-aluminum composites were successfully used for water filtration. Magnetic separation permits the processing flexibility for biochar recycling. Morphological, structural, and physico-chemical characteristics of unmodified and modified biochars were characterized using BET surface area, XRD, XRF, SEM, SEM- EDX, TEM, FTIR, XPS, pHpzc, CHNS, proximate and ultimate analysis. Unmodified and modified biochars were successfully remediated organic and inorganic compounds including dyes, pharmaceuticals, oil, heavy metals, actinides, lanthanides, microplastics, arsenate, arsenite and other oxyanion species and perfluoroalkyl substances. These contaminants were recovered and biochars were recycled. Rice and wheat husks were copyrolyzed after soaking in aqueous FeCl3 to prepare iron oxide-biochar composites for aqueous arsenic removal (96-111 µg/g). Banana peel biochars removed aqueous ciprofloxacin (23.3 mg/g) and acetaminophen (57.3 mg/g). Highly persistent per- and poly-fluoroalkyl substances (PFAS) sorption from ppb levels onto biochar and its magnetic Fe3O4- containing variant were studied. Novel biochar-based hydrophobic, floating, magnetic, sorptive and multi-functional adsorbent composites were synthesized for oil removal. Sustainable biochar sorbents application in water filtration is strongly dependent on biochar production conditions (e.g., feed type, pyrolysis temperature, residence time, pressure), and water physico-chemical characteristics and by batch or column implementation.
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