Glutaraldehyde removal from produced water using photolysis and photocatalysis

Abstract

Glutaraldehyde (GA) has been used extensively as a biocide in hydraulic fracturing fluids leading to the contamination of the compound in produced water. In this study, the performances of photolysis and photocatalysis for removal of GA in synthetic produced water were investigated. Photolysis of GA was performed under ultraviolet (UV). GA can be photolyzed by UV at all studied conditions with the removal ranging from 52 to 85% within one hour irradiation. Photolysis of GA followed pseudo-first order kinetics. The degradation rate of GA increased with increasing incident light intensity and decreasing pH. Increasing initial GA concentration resulted in decreasing rate of GA degradation. Photocatalysis of GA used Ag/AgCl/BiOCl as a photocatalyst. Visible light bulbs emitting light at 419 nm were used for photocatalysis. Removal of GA at 0.1 mM in 200 g/L NaCl solution at pH 7 was 90% after 75 min irradiation using 5 g/L of the photocatalyst. The removal rate of GA markedly increased with increasing pH (5-9) and photocatalyst loading (2-8 g/L), and under 350 nm UV (compared to visible light). The removal rate of GA substantially decreased at higher NaCl and GA concentrations. The removal of GA under natural sunlight was slightly better than that under 419 nm. This study helps in addressing an obstacle associated with produced water treatment and disposal. After removing GA from produced waters, biological treatment, which is economical, will become a viable option for treatment of the waters for potential hydraulic fracturing reuse, or will make the waters less harmful after disposal. The work also provides an effective treatment scheme for a common biocide in produced water.