Removing silicon species from hydrocarbon solvents such as cyclohexane. The process comprises contacting the hydrocarbon solvent with sulfuric acid in an amount sufficient to phase separate the silicon species and removing at least 20% by weight of the residual silicon species from the hydrocarbon solvent. The hydrocarbon solvent may be a polymerization solvent containing residual silicon species, and more than 80% by weight of the silicon species can be removed.