Treatment of fracturing fluid waste by Fenton reaction using transition metal complexes catalyzes oxidation of hydroxypropyl guar gum at high pH

Hydroxypropyl guar gum (HPGG), polyacrylamide (PAM) and carboxymethyl cellulose (CMC) are widely used as thickeners in fracturing fluids, and thus contaminate wastewater. We designed a clean oxidation process for the treatment of waste fracturing fluids containing hydroxypropyl guar gum and other polymers under high pH value. For that, 1,10-phenanthroline(L)-transition metal complexes were prepared and screened for viscosity reduction of hydroxypropyl guar gum oxidized by hydrogen peroxide (H2O2). Results show that Cu(II)L exhibited high catalytic performance for the degradation of hydroxypropyl guar gum in a pH range of 7–14. Under the optimum experimental conditions, the viscosity of hydroxypropyl guar gum solution can be reduced effectively with 10.0% H2O2 and 5.0% Cu(II)L. The chemical oxygen demand (COD) of the hydroxypropyl guar gum solution decreased from 8 g/L to 65 mg/L. Cu(II)L also showed a high catalytic ability for the degradation of various polymers.