In Thailand, onshore drill cuttings (DC) contaminated with total petroleum hydrocarbon (TPH) are currently transported off-site for incineration, causing high transportation cost and potential leakage to the environment. To address the issues, we develop solvent-based washing as a greener alternative for onshore DC remediation, focusing on solvent selection, washing process optimization, and solvent recovery. The results showed that ethyl lactate (EL) was the best green solvent for DC washing, compared to water, ethylene glycol, and ethyl acetate. Based on response surface methodology assisted with central composite design, the maximum TPH removal of 87.1% was achieved from 4 mL g-1 liquid-to-solid ratio, 14 min washing time, and 80 rpm stirring speed, and the TPH removal rate by EL fitted well with the second-order reaction (R2 = 0.9774). Furthermore, the spent EL was successfully recycled by simple and low-energy adsorption using granular activated carbon (GAC). With the sufficient GAC dosage, TPH could be completely removed from the spent EL without impairing the original EL properties. Moreover, the recycled EL exhibited its successful reuse in the subsequent DC washing process. These findings suggest that solvent washing accompanied with solvent recovery by adsorption could be a novel and greener remedial scheme for onshore DC management.
Keywords: Drill cuttings; Green solvents; Optimization; Solvent recovery; Total petroleum hydrocarbon.
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