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Abstract Fuel components such as benzene, toluene, and methyl tertiary-butyl ether (MTBE) are frequently detected pollutants in groundwater resources. Ex-situ remediation technologies by activated carbon have been used for treatment for many years. However, due to high cost of these technology, more attention has been given to the in-situ remediation methods of contaminated groundwaters using liquid carbon adsorbents. Literature search showed limited studies on using adsorbents in liquid form for the removal of such contaminants. Therefore, this lab-scale study investigates the capacity of using raw biochar-based liquid activated carbon and iron-modified biochar-based liquid activated carbon to remove these pollutants. The adsorption efficiency of the synthesized liquid activated carbon and iron-modified liquid activated carbon mixed with sand, limestone, and 1:1 mixture of sand/limestone, was tested using batch suspension experiments. Adsorption by granular activated carbon was also investigated for comparison with liquid activated carbon. Results of the study revealed that mixing of liquid activated carbon or LAC-Fe on subsurface materials had not improved the removal efficiency of MTBE. At the same time, it showed a slight improvement in the adsorption efficiency of benzene and toluene. In all cases, the removal by GAC was higher with around 80% and 90% for MTBE and BT, respectively. Results also showed that benzene and toluene were better removed by liquid activated carbon and iron-modified liquid activated carbon (∼ 40%) than MTBE (∼ 20%). It is also found that water chemistry (i.e., salinity and pH) had insignificant effects on the removal efficiency of pollutants under the study conditions. It can be concluded that more research is needed to improve the capacity of biochar-based liquid-activated carbon in removing MTBE, benzene and toluene compounds that will lead to improve the utilization of liquid activated carbon for the in-situ remediation of contaminated groundwaters.

Methyl tertiary-butyl ether (MTBE) and BTEX (benzene, toluene, ethylbenzene, and xylenes) are common groundwater contaminants that pose significant health risks. This study investigated the efficiency of a colloidal activated carbon (CAC) material in removing MTBE and BTEX from contaminated water using batch and continuous core flooding systems. In the batch system, a mixture of sand and carbonate was coated with 1-3 g of CAC for the removal of contaminants. The core flooding system was packed with similar materials and mixed with 10 g of CAC. X-ray diffraction (XRD) revealed that the carbonate consists of more than 97% calcite, with traces of clay and quartz minerals. On the other hand, the sandstone sample showed around 89% quartz, 8% clay minerals, and traces of feldspar. The CAC has a surface area of 1050 m 2 /g, mean particle size of 31.8 μm, density of 1.0976 (g/cm 3 ), viscosity of 24.4 mPa·s, and a negative surface charge. Spiked water samples with 2000 ppb MTBE and BTEX concentrations ranging between 1000 and 200 ppb were injected through the system at rates of 0.5 and 1.0 mL/min. The results showed that the type of packing materials and flow rate have a significant impact on contaminant removal. For example, the removal efficiency was higher in sandstone due to uniform particle shapes facilitating better water distribution and CAC accessibility within the pore medium. A lower injection rate (0.5 mL/min) resulted in higher removal efficiencies due to increased contact time between contaminants and CAC. At 1 mL/min, the maximum removal of 94% and 65% for MTBE and benzene was achieved in carbonate, while 99% and 96% were achieved in sandstone, respectively. At 0.5 mL/min, complete MTBE removal and over 95% benzene removal were achieved in both materials. Overall, the CAC demonstrated excellent MTBE and BTEX removal capabilities, exceeding 95%, offering a promising approach for in situ groundwater remediation., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)