Abstract: Some embodiments relate to methods and apparatus for mitigating high metal concentrations in photoresist residue and recycling sulfuric acid (H2SO4) in single wafer cleaning tools. In some embodiments, a disclosed single wafer cleaning tool has a processing chamber that houses a semiconductor substrate. A high oxidative treatment unit may apply a high oxidative chemical pre-treatment to the semiconductor substrate to remove a photoresist residue having metal impurities from the semiconductor substrate in a manner that results in a contaminant remainder. A SPM cleaning unit apply a sulfuric-peroxide mixture (SPM) cleaning solution to the semiconductor substrate to remove the contaminant remainder from the semiconductor substrate as an SPM effluent. The SPM effluent is provided to a recycling unit configured to recover sulfuric acid (H2SO4) from the SPM effluent and to provide the recovered H2SO4to the SPM cleaning unit via a feedback conduit.