Utilization of Industrial Wastes as Catalyst or Catalyst Support for Photocatalytic Treatment of Synthetic and Simulated Pulp Bleaching Wastewaters

In the present study, the performance of industrial wastes as a catalyst and/or catalyst support was investigated for the photocatalytic treatment of synthetic and simulated pulp bleaching wastewaters. The treated effluent treatment plant sludge from a steel industry was used as a catalyst (SS_HCl) alone or in conjunction with TiO2 or ZnO. Moreover, the black liquor (BL) from a pulp and paper mill was utilized for deriving catalyst supports, that is, carbonized material (C_BL) and activated carbon (AC_BL). TiO2/SS_HCl/AC_BL and SS_HCl/C_BL catalysts showed favorable catalytic properties (surface area = 377 and 268 m2 g–1, respectively). During photocatalytic oxidation, total organic carbon (TOC) removal of 65–67% could be achieved from synthetic wastewater samples (initial TOC = 110 mg L–1). The presence of radicals during the photocatalytic process was also confirmed. The chlorophenols' oxidation kinetic data could be fit adequately in the Langmuir–Hinshelwood model. Apart from this, reusability potential of the catalysts was also investigated.