Advances in biosorbents for removal of environmental pollutants: A review on pretreatment, removal mechanism and future outlook

Heavy metal toxicity has proven to be a major threat and there are several health risks associated with it. The toxic effects of these metals, even though they do not have any biological role, remain present in some or the other form harmful for the human body and its proper functioning. They sometimes act as a pseudo element of the body while at certain times they may even interfere with metabolic processes. Few metals, such as aluminium, can be removed through elimination activities, while some metals get accumulated in the body and food chain, exhibiting a chronic nature. Various public health measures have been undertaken to control, prevent and treat metal toxicity occurring at various levels, such as occupational exposure, accidents and environmental factors. Metal toxicity depends upon the absorbed dose, the route of exposure and duration of exposure, i.e. acute or chronic. This can lead to various disorders and can also result in excessive damage due to oxidative stress induced by free radical formation. This review gives details about some heavy metals and their toxicity mechanisms, along with their health effects. Show more

Biochar is a stable carbon-rich by-product synthesized through pyrolysis/carbonization of plant- and animal-based biomass. An increasing interest in the beneficial application of biochar has opened up multidisciplinary areas for science and engineering. The potential biochar applications include carbon sequestration, soil fertility improvement, pollution remediation, and agricultural by-product/waste recycling. The key parameters controlling its properties include pyrolysis temperature, residence time, heat transfer rate, and feedstock type. The efficacy of biochar in contaminant management depends on its surface area, pore size distribution and ion-exchange capacity. Physical architecture and molecular composition of biochar could be critical for practical application to soil and water. Relatively high pyrolysis temperatures generally produce biochars that are effective in the sorption of organic contaminants by increasing surface area, microporosity, and hydrophobicity; whereas the biochars obtained at low temperatures are more suitable for removing inorganic/polar organic contaminants by oxygen-containing functional groups, electrostatic attraction, and precipitation. However, due to complexity of soil-water system in nature, the effectiveness of biochars on remediation of various organic/inorganic contaminants is still uncertain. In this review, a succinct overview of current biochar use as a sorbent for contaminant management in soil and water is summarized and discussed. Show more

Biochar is used for soil conditioning, remediation, carbon sequestration and water remediation. Biochar application to water and wastewater has never been reviewed previously. This review focuses on recent applications of biochars, produced from biomass pyrolysis (slow and fast), in water and wastewater treatment. Slow and fast pyrolysis biochar production is briefly discussed. The literature on sorption of organic and inorganic contaminants by biochars is surveyed and reviewed. Adsorption capacities for organic and inorganic contaminants by different biochars under different operating conditions are summarized and, where possible, compared. Mechanisms responsible for contaminant remediation are briefly discussed. Finally, a few recommendations for further research have been made in the area of biochar development for application to water filtration. Show more