Green aerogel adsorbent for removal of organic compounds in shale gas wastewater: High-performance tuning and adsorption mechanism

Abstract

The complex organic compounds in shale gas flowback and produced water (SGFPW) pose threats to environmental safety and aggravate membrane fouling during membrane combined processes for SGFPW reuse. The high adsorption efficiency and capacity of aerogel revealed the tremendous potential for removing organics from SGFPW. In this study, we utilized a facile tuning method for porous biochar aerogel (PBA) to improve the adsorption performance of organic compounds in SGFPW as well as identified the adsorption mechanism by analyzing the organics characterization and PBAs’ physicochemical properties. The PBAs were tailored by altering urea and KOH concentration, and the maximum adsorption removal (56.4%) and capacity (205.86 mg/g) of dissolved organic carbon (DOC) was obtained by the optimally tuned PBA-A11.5U12.0 (PBA tuned by 11.5 wt% KOH and 12.0 wt% urea) with a fast adsorption rate (0.012 g/(mg·min)), exceeding the DOC removal from shale gas wastewater by other carbon adsorbents reported. The characterization of organic compounds in SGFPW was identified by measuring fluorescence compounds and organic fractionation, which showed that the humic substances, aromatic proteins, and hydrophobic organics were much tended to be adsorbed by PBAs. Combined with principal component analysis, the organics adsorption mechanism was further identified, indicating the considerable contribution of electron-donor–acceptor interaction, hydrophobic effect, and hydrogen-bond formation. Such a high-efficiency tuned PBA showed decent adsorption performance for various SGFPW as well as good reusability. And it was fabricated from biopolymer with low cost, thus possessing promising prospects in SGFPW treatment.