Purified residues from the production of biogenic silica as resources for the remediation of oilfield produced water: A strategy for phenol removal

[Display omitted] •Biogenic silica wastes modified for TOC removal and treatment of oilfield-produced water;•The adsorbent showed a large surface area of over 1000 m2/g;•The adsorbent was highly recyclable, being reused in up to 15 cycles;•CAM adsorbent removed 73 % of TOC from real produced water in 150 min. The escalating fuel demand generates significant volumes of oilfield-produced water containing complex environmental pollutants such as phenol. This study proposes a purification method for converting activated carbon (CAM), obtained at zero cost as a by-product of biogenic silica production, into an effective adsorbent. The activated carbon was characterized extensively for its morphological, structural, and chemical properties, revealing a substantial surface area exceeding 1000 m2/g. The adsorption process for phenol removal was investigated through kinetics, isotherms, and thermodynamic analyses. Kinetic data analysis favored the PSO models within 150 min, while equilibrium studies showed the best fit for the Sips and Liu models. CAM achieved an adsorption capacity of 23.9 mg g−1 for phenol removal at pH 6, the typical pH of produced water. The adsorption process was found to be exothermic and spontaneous. The produced adsorbent demonstrated high recyclability, with up to 15 reuse cycles achievable through regeneration via thermal desorption at 180 °C. Furthermore, CAM removed 73 % of total organic carbon from real produced water within 150 min. Thus, using activated carbon intrinsically carbonized during silica production is an economically viable and attractive solution for treating phenol-contaminated oilfield-produced water.