Abstract
Eco-friendly biochar produced from cost-effective and readily available agricultural waste will likely pose no threat on the aqueous phases, other environmental media, human health and emission of greenhouse gases to the atmosphere. Optimising biochar for an intended application could require careful selection of a biomass feedstock as well as production pyrolysis technique and conditions for the production of biochars with specific characteristics. Previous studies have explores the relationships that exist between biochar production conditions, characteristics, and possible end-uses of biochar. This review provides an overview of the production and utilisation of biochar as absorbents for adsorption of trace metals in contaminated aqueous environment. Biochar has great affinity to adsorb molecular ions that is making it possible to be used for various toxicological remediation strategies. It has proven effective and useful for mitigating aqueous metals, organic compounds, suspended solids, and organic hydrocarbons in a various kind of industrial applications such as urban and residential storm water runoff, landfill leachates, industrial runoff, resource extraction runoff, and industrial wastewater filtration. Specifically designed biochar could be very effective in the removal of trace metals from contaminated aqueous environment. The multiple factors that determine the adsorption of the trace metals in aqueous environment or phases needs to be carefully examined. Cost-effectiveness of biomass feedstock and eco-friendliness of techniques need to also be given much consideration by way of making comparison with existing contaminant mitigation technologies.
Highlights
Biochar is produced from biomass or feedstock pyrolysis which is a process that involves breaking down of organic substances at temperatures that ranged from 350 °C to 1000 °C in a low-oxygen thermal process [1]
Biochars characteristics and properties are greatly affected by the original of feedstock, the pyrolysis process and its parameters
The adsorption capacity for trace metals is highly dependent on the experimental conditions that include adsorbent particle size, contact time, competing trace metals, dosage of biochar, pH, metal concentration, and temperature of the leaching solution
Summary
Biochar is produced from biomass or feedstock pyrolysis which is a process that involves breaking down of organic substances at temperatures that ranged from 350 °C to 1000 °C in a low-oxygen thermal process [1]. The cost involved in the use of adsorption technology can be reduced provided the adsorbent is cheap [4] It is mostly used because of its effectiveness as physical method of separation for removal or minimisation of the concentration of organics and inorganics contaminants in the aqueous environment by application of most common adsorbents which include activated carbon, aluminium oxide and silica gel [5]. Trace metals occur naturally can be found in aqueous environment from a pedogenetic processes that involves weathering of parent materials at levels that can be regarded as trace (less than 1000 mg/ kg) and rarely toxic [11,12] Anthropogenic activities such as electroplating, energy and fuel production, mining, melting operations, intensive agriculture, smelting, sludge dumping, and power transmission, are the major contributor to trace metals contamination [9]. The mining sector and landfilling sites for waste are major contributing sources of trace metals contamination in aqueous environment
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