Mechanisms of boron removal from hydraulic fracturing wastewater by aluminum electrocoagulation

摘要: Abstract Hypotheses Boron uptake from highly saline hydraulic fracturing wastewater by freshly precipitated amorphous Al(OH)3 precipitates is due to ligand exchange and complexation with surface hydroxyl groups. Consequently, aluminum electrocoagulation can be a feasible approach remove boron flowback/produced water. Experiments Actual containing ∼120 mg/L the Eagle Ford shale play was employed. Electrocoagulation performed over range of dosages (0–1350 mg/L), pH 6.4 8, high current densities (20–80 mA/cm2) using cylindrical anode encompassed porous 316-stainless steel cathode. Direct measurements along its chemical state coordination were made Attenuated Total Reflection-Fourier Transform Infrared spectroscopy (ATR-FTIR) X-Ray Photoelectron Spectroscopy. Findings removal increased monotonically dosage higher at but remained relatively constant ⩾20 mA/cm2. Chloride ions induced anodic pitting super-Faradaic (131% efficiency) dissolution their electrooxidation produced free chlorine. ATR-FTIR suggested outer-sphere inner-sphere trigonal B(OH)3 Al(OH)3, which confirmed B O bond shifting toward lower binding energies in XPS. Severe Al interferences precluded evidence for tetrahedral B(OH)4− complexation. No co-precipitation obtained.