Multifunctional Carbon Aerogel Granules Designed for Column Reactor for Efficient Treatment of Shale Gas Flowback and Produced Water

Abstract

Shale gas flowback and produced water (SGFPW) greatly hinders sustainable shale gas development and can cause severe environmental threats without proper treatment. Aerogel is an advanced adsorption material for treating SGFPW with complex components; nevertheless, there is little investigation on the aerogel adsorbent designed for SGFPW treatment on-site. Herein, we report a facile and green method for preparing carbon aerogel granules (CAGs) with porous biochar aerogel (PBA) incorporated on physically cross-linked chitosan matrix for high-performance treatment of SGFPW. CAGs exhibit good elasticity with Young’s modulus of 49 kPa for practical use and ultra-high water adsorption ratio of 1936.7% for fast liquid-phase mass transfer of pollutants from SGFPW to CAGs. CAGs show high removal rates for various organic pollutants in SGFPW, including ≥ 36.6% of dissolved organic carbon (DOC), ≥ 72.2% of UV254, and ≥ 92.2% of total fluorescent organic compounds within 60 min. Meanwhile, CAGs allow steady adsorption of heavy metals such as Zn (18.8–21.7%), Co (20.1–23.7%), Cu (18.4–29.8%), Pb (32.5–62.1%), and Al (54.8–58.1%) in SGFPW. The adsorption of dissolved organic pollutants in SGFPW by CAGs is mainly based on their π-π electron-donor-acceptor (EDA) interaction with the PBA carbon skeleton, while the adsorption of heavy metals based on their complexation with the N and O atoms of PBA. CAGs are suitable for the fixed bed to treat SGFPW, which displays good binary functions of filtration and adsorption, showing high potential for treating SGFPW on-site.

Keywords: Shale gas flowback and produced water, Carbon aerogel granules, Adsorption, organic compounds, heavy metals