Microwave heating system for CuFe2O4/rGO/PMS enhanced catalytic-oxidative pre-treatment, water, and salt recovery from reverse osmosis reject of textile industry effluent

Abstract

Microwave (MW) heating mechanism was investigated for reverse osmosis (RO) reject management of real textile effluent, i.e., pre-treatment, water, and salt recovery. For pre-treatment, microwave-induced catalytic degradation (MICD) enhanced with CuFe2O4/rGO for PMS activation was applied for organics degradation. The synthesized CuFe2O4/rGO (average particle size ∼16.44 nm) was characterized for XRD, SEM with EDAX, FTIR, VSM and TGA. MICD (1 g/L catalyst (80 %:20 %), 400 mg/L PMS, 90℃ MW temperature, 450 W MW power, and pH 11.32) showed 100 % color, 80.4 % TOC, and 91.1 % COD reduction within 16 min of MW irradiation. Radical quenching studies and EPR analysis revealed that SO4•− and ⦁OH were the dominant reactive species followed by non-radical O21. Recyclability study of CuFe2O4/rGO showed 72 % color, 65 % TOC, and 71.4 % COD removal after 5 cycles. XRD and FTIR of reused CuFe2O4/rGO hold similar crystallinity and structural properties as fresh catalyst. ATR-FTIR spectrum of before and after degradation of RO reject showed considerable degradation of organic dye molecules. Subsequently, the MW heating system was optimized for water recovery (110℃ MW temperature, 700 W MW power, and 100 mL reject volume), showing 100 % water recovery within 6 min, and its characterization showed a high distillate purity. NaCl and Na2SO4 salts were recovered under different MW operating temperatures, exploiting solubility equilibrium, and characterized for XRD, SEM with EDAX, and PSA.