Treatment for high-concentration liquid crystal wastewater with a novel Fenton–SBR–microwave pyrolysis integrated process

Abstract

Abstract A novel Fenton–SBR–microwave pyrolysis integrated process is developed to treat liquid crystal wastewater possessing complex components, high toxicity and strong stability. In this integrated process, Fenton–SBR and microwave pyrolysis are for the removal of chemical oxygen demand (COD) and disposal of iron mud generated in the Fenton process respectively. The effects of H2O2:Fe2+ molar ratio and Fenton dosage on COD removal were optimized. The experimental results revealed that the removal efficiencies for COD and total organic carbon (TOC) were 99.8% and 99.2%, and the values for MLSS and SVI were stable at 4,500 mg L–1 and 65%, respectively. Microscopic examination proved that there were rotifer, Epistylis galea, Opercularia coarctata, vorticella and mormon genus which are indicative microbes for good water quality. Iron mud waste produced in the Fenton reaction was handled with microwave pyrolysis, producing ɑ-Fe2O3 commercial byproduct. The estimated cost including chemical reagents and electricity for this integrated process is about $320 T–1, without consideration of the added value of the ɑ-Fe2O3 byproduct. TOC removals in the Fenton and SBR processes both fit well with pseudo-first-order kinetics and the corresponding half-life times are 0.15 and 7 h, respectively.