Crop straw biochar enhances hydrocarbon adsorption in ground water

Hydrocarbon fuel production and use can pose environmental risks, such as spills during extraction and transportation, which can contaminate soil, damage vegetation, adversely affect human and animal health, and contaminate ground water with soluble hydrocarbons, that could spread to surrounding areas. Our study evaluates the simultaneous adsorption capacity of canola straw biochar for 12 hydrocarbon pollutants in ground water from a northern peatland. This approach simulates the simultaneous contamination of multiple hydrocarbon classes in a complex aqueous matrix. In the laboratory, canola straw biochar remediated benzene, toluene, ethylbenzene, and xylene (BTEX), and linear chained and polycyclic aromatic hydrocarbons from ground water. BTEX concentrations significantly decreased with application of 1 g L^-1 biochar, achieving a remediation efficiency of over 95 % within 7 days. Increasing application rates enhanced remediation efficiency, exceeding 99 % at a 2 g L^-1 application rate. Hydrocarbon adsorption on biochar is a complex process involving surface interactions and diffusion-controlled steps, with the kinetic data fitting well to models indicative of chemisorption. X-ray photoelectron spectroscopy, BET/CO₂ porosimetry and Fourier transform infrared spectroscopy corroborated theoretical isotherm and kinetic models, indicating that functional groups on the biochar surface play a crucial role in adsorption, primarily through hydrophobic and π-π interactions. The results enhanced our understanding of adsorption mechanisms for multiple hydrocarbon classes in complex matrices under controlled laboratory conditions, and positioned canola straw biochar as an effective remediation technique for hydrocarbon water treatment. Biochar is made from waste agricultural materials and sequesters carbon, contributing to environmentally sustainable remediation and a circular economy.