Absorption Water Treatment Potential of Crop-Waste Biochar Made by Controlled and Uncontrolled Pyrolysis: An Investigation into Converting Biowaste to Bioresource for the Developing World
Bhattacharia, Sanjoy K.
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Access to clean water is an issue that persists in many developing countries. Available water is often polluted from inadequately treated agricultural, industrial, and human wastes. There are many ways to address environmental challenges for polluted water including source water protection, altering the use patterns of water, and treating heavily polluted water sources before they mix with other, cleaner waters. Employing water protection and water treatment strategies in developing world contexts in particular is often challenging due to a lack of financial resources, industrial infrastructure, and technical know-how. One approach to bridge the gap between the developed “well resourced” world and the developing “limited resource” world is to make use of materials readily available, even waste materials, to treat water and minimize solid and hazardous waste generation. Biochar is such an application of this approach. It is a microporous, carbon-rich adsorbent material that can be made from any virtually any kind of waste biomass or other waste organic material. Since many developing world communities are highly agrarian, people in those communities have access to a large amount of crop and animal waste which can be used as biochar feedstock. In our study, we made crop-waste (rice hull, pecan shell, cottonseed) biochar using temperature-controlled pyrolysis in a muffle furnace (MF) reminiscent of the kinds of high technology, high resource process in the developed world. We contrast that with biochars made from a simple and easily built top-lift updraft (TLUD) pyrolysis process that would not be difficult for developing world communities to appropriate in their local context with biomass they have on hand. We looked specifically at the contrasting abilities of these two types of biochar, MF and TLUD, to adsorb cationic and anion colored dyes in water through controlled shaking experiments. Quantitative examination of the amount of dye that can be removed, on different biochar, and at differing pH helped to discern the mechanism of adsorptive interaction on the biochars. We then relate the way the biochar was made, in light of the material from which it was made, to the adsorptive performance we saw in the dyes. These comparisons provide fundamental understanding into the nature of ionic pollutant surface interactions on biochars. This understanding can be used to design treatment processes for industrial, sanitary, storm-, and agricultural wastewater in both developing and developed worlds.