Development of Fenton Process with Sludge Reuse for the Treatment of Wastewater from a Pharmaceutical Industry Producing Anticancer Active Ingredients

Wastewater from pharmaceutical industries cannot be properly treated in conventional purification plants. Fenton process is an effective method to treat these effluents whose applicability, however, is hampered by the necessity of dispose of a large quantity of sludge that is produced by the removal of the catalyst from the liquid phase after the treatment. To overcome these drawbacks, in this work a suitable procedure for the recovery and reuse of sludge, was developed. The experiments were conducted by treating wastewater generated from the production of anticancer active ingredients. The homogeneous Fenton process was initially optimized and temperature of 40 °C, dosages of peroxide RHC=2 gH2O2/gCOD and catalyst RIC=0.4 gFe2+/gCOD were identified as the most suitable operating conditions that allowed to reach removals of chemical oxygen demand (COD) of approximately 68%. The oxidation treatment was found to be very fast following a pseudo second-order kinetic law and reaching the stationary state in a treatment time of only 30 min. Afterwards, the sequential fractional addition of peroxide and the reuse of sludge were investigated. By feeding the H2O2 dosage in two subsequent aliquots, COD removal increased up to 78% and the biodegradability reached 61%. By reusing the sludge produced by the gradual dosing of H2O2, the efficiency was equal to that with the fresh catalyst in the first reusing cycle and around 55% in the fifth cycle. With the addition of H2O2 in two fractionated doses, a supplementation of 10% of the dosage of pure catalyst permitted to maintain efficiencies always above 78%.