Activated carbon from baobab fruit shells through domestic processes

Surface and groundwater pollution is rampant due to poor waste management and runoff. Dry regions of the country also writhe from water scarcity which leaves communities to resort to unsafe water supplies for domestic use. It is estimated that about 90% rural households in Zimbabwe consume untreated water (Hoko, 2005) and that more than 75% of Zimbabwe's population lives under water stressed conditions in most rural areas (Manyanhaire et al., 2009). Commercially produced activated carbon is expensive. The aim of the research was to investigate the production of activated carbon from baobab fruit shells (a cheap raw material) using a method that can be employed at rural homesteads in removing organic pollutants. Two methods of producing activated carbon were also compared i.e. activating before carbonization and activating after carbonization. Activating with salt after carbonization proved to be the efficient (adsorption% 93.2). A contact time of 60 minutes was determined as the maximum time required for adsorption and a pollutant concentration equivalent to 0.3M oxalic acid gave the highest adsorption of 98.9%. The activated carbon from baobab fruit shells follows a Langmuir isotherm which explains the existence of a monolayer and the saturation of adsorption sites on the activated carbon. It was concluded that activated carbon from baobab fruit shells have the potential of removing organic pollutants from water.Keywords: activated carbon, percentage adsorption, carbonization, adsorption, organic pollutants and fruit shell

Moving towards resource efficiency and circular economy in the brick manufacturing sector in Zimbabwe

The life cycle assessment of the ABC (Pvt) Ltd brick manufacturing plant has considered land use, fossil resource scarcity, water consumption, global warming and fine particulate matter formation as the impact categories for assessment, with clay mining and coal as the input flows with the highest significant contributions to environmental load. The phase of clay mining (65.8%) is significantly impacting on all the investigated impact categories followed by brick moulding (24.8%) and brick roasting (9.4%) phases, respectively. Hotspots were assessed to identify potential for resource efficiency and circular economy at ABC bricks, Zimbabwe. It can be concluded that ABC is severely polluting the air with emissions above the Environmental Management Agency (EMA) standards for SO2, CO, PM and NOx thus putting kiln workers at risk of respiratory diseases. The calculated Air Quality Index (AQI) ranks CO as the most affecting pollutant with an average score of ∼600. Clay production efficiency was also determined, and an analysis revealed that extrusion and clamping stage contributed highly to the clay losses during brick moulding. Therefore, focus must be placed on these process steps to reduce raw material losses. Furthermore, an environmental waste (fly ash) was used in different weight percentage ratios of 10%, 20% and 100% to substitute clay. The increase of the fly ash content in the brick making process proved to significantly reduce the environmental load among the selected impact categories. ABC uses clay as its main raw material hence the high demand for clay. Strategies should include accounting of used clay daily and raw materials substitution. If ABC uses fly ash from its brick kilns and from other thermal power plant boilers to mix with clay in brick production, then the quantity of clay demanded will be reduced. Using fly ash will reduce rate of clay extraction while at the same time solving the problem of fly ash disposal in Zimbabwe. This circular option will ultimately result in reduced pit expansion, hence reducing top-soil loss and environmental degradation. It should not be disregarded that top-soil loss in turn affects food security. By adopting appropriate technologies, implementing resource efficiency, and designing circular economy patterns, the brick manufacturing sector in Zimbabwe may not only reduce production waste but also comply with enforced environmental protection legislation