REMOVAL OF LIGNIN IN PULPING WASTEWATER BY HETEROGENEOUS FENTON-LIKE PROCESS USING IRON MOLYBDATE

Abstract

Pulping industry consumes high amount of raw materials and chemical reagents in each process and wastewater problem from Pulp industries is one of the most concern. One of concerned wastes is black liquor which contains high lignin content. Lignin causes environmental problems such as increase oxygen demand and can be changed to be toxic by-products such as phenols, ketone and carboxylic acids. Therefore, wastewater treatments are required before discharge to environment. This research studied on the treatment of synthetic pulping wastewater. The treatment of synthetic pulping wastewater was carried out by Fenton process using ferrous sulfate and heterogeneous Fenton-like process using iron molybdate to find the optimum conditions for color and lignin removal. Furthermore, iron molybdate was reused to find its durability. The initial lignin concentration of synthetic pulping wastewater was 910 mg/l. The result of Fenton process showed that at pH of 3, Fe2+:H2O2 ratio of 1:2.5 and Fe2+ dosage was 400 mg/l achieved 92%, 90% and 92% for lignin, color and COD removal efficiencies, respectively. The result of heterogeneous Fenton-like process showed that at pH of 8, Fe3+:H2O2 ratio of 1:10 and 2 g/l Fe3+ dosage, lignin, color and COD removal efficiency were achieved 71%, 67% and 67%, respectively. Moreover, iron molybdate could maintain its durability after four times reuse. Although using of iron molybdate in heterogeneous Fenton-like process showed lower performance than using of ferrous sulfate in Fenton process, it could overcome several drawbacks of Fenton process e.g. no sludge iron, could be applied in wide range of pH, and maintain its performance after several times reused.