| Steady increase in the natural gas production in U.S.A. is mainly due to horizontal drilling and hydraulic fracturing (fracking) technologies. Three to five million gallons of water are used for fracking a well. Approximately, 30% of the water flows back to the surface after fracking a well, forming a huge waste stream. Also, disposal of flowback is a major barrier to the development of new shale gas plays. Spent fluid cracking catalyst (FCC), a refinery waste is proposed as an agent for treatment of flowback, another waste stream. Characteristics of fresh FCC, deactivation in FCC, properties of spent FCC are studied to enhance the understanding of the adsorption potential of spent FCC. Batch adsorption study is conducted to examine the adsorption of acetic acid, a very common organic in flowback, from aqueous solution with change in initial concentration and pH. Equilibrium adsorption data fit the Freundlich isotherm. Initial concentrations of acetic acid were selected from the typical concentration range in flowback, for the adsorption experiment. Adsorption capacity was observed to increase with increase in the initial concentration of acetic acid. Adsorption capacity decreased with increase in pH at 25 mg/L and 40 mg/L initial concentrations. The adsorption capacity change with pH is not monotonic at 10 mg/L and 55 mg/L concentrations. The primary adsorption mechanism is supposed to be through adsorption of undissociated acetic acid molecules on coke, matrix, and the Si=O=Si sites in the zeolite in spent FCC. |
