Processes for removing oil from a solid wellbore material such as drill cuttings or water such as produced by a subterranean formation include contacting the solid material/water with an amino-substituted polymer such as chitosan and a halogenating agent. The oil separates from the solid material and becomes bound within a flocculated solid. The flocculated solid containing the oil subsequently may be combined with a solvent of the amino-substituted polymer. Further, the flocculated solid may be contacted with a reducing agent, converting the flocculated solid back into the amino-substitute polymer and forming an oil-phase separate from the solvent-phase. The oil-phase may then be separated from the solvent phase and recovered. The solvent in which the amino-substituted polymer is dissolved may be recycled for treating more solid material removed from the well bore.