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.

In this work, bio-char, a mass productive by-product of biomass fast pyrolysis, was adopted as an adsorbent to remove tetracycline (TC) from aqueous solution. To enhance the adsorption capacity, a simple modification of bio-char with acid and alkali was carried out. Bio-char samples were characterized by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption isotherm. The results show that the alkali treated bio-char possesses larger surface area than those of raw and acid treated bio-chars, and accordingly exhibits a more excellent adsorption performance (58.8 mg/g) than the other two bio-chars and other adsorbents reported previously. The graphite-like structure of bio-char facilitates the formation of π-π interactions between ring structure in tetracycline molecule and graphite-like sheets. The surface area showed significant effects on TC adsorption as well as O-containing functional groups, whereas the initial pH of solution has small effects on TC adsorption under the experimental conditions. Copyright © 2012 Elsevier Ltd. All rights reserved.