Performance and optimization of diclofenac and ibuprofen adsorption onto activated carbon synthesized from sunflower seed shell (Helianthus annuus) in natural groundwater samples

In this study, activated carbon (AC) obtained from biomass waste materials (sunflower seed shells -SSS) was synthesized by combining chemical (H₃PO₄ 80% wt.) and thermal activation (at 544 °C). Synthesized AC exhibited a BET surface area of 1531 m² g⁻¹, and pore volume of 0.98 cm³ g⁻¹. The material exhibited various surface functional groups, such as P₂O₇, C-O-P and -COOH, O = C, as well as a moderate graphitization degree (I_D/I_G < 1) and acidity caused by H₃PO₄ treatment. Moreover, its morphology and physicochemical features were evaluated by SEM–EDS, TGA, XPS, Raman, and FT-IR techniques. The material was used to study the adsorption of anti-inflammatory pharmaceutical compounds such as ibuprofen (IBF) and diclofenac (DIF) present in natural groundwater samples. The effects of parameters such as pH, activated carbon dose, temperature, and IBF or DIF initial concentration were optimized by using a central composite design (CCD). The results revealed that optimum conditions to remove DIF and IBF from natural groundwater samples were pH of 8.0 and 7.0, an AC dose of 0.79 and 1.0 g L⁻¹, and a contact time of 60 min for DIF and IBF, respectively. A successful procedure to desorb both pollutants from adsorbent by using acetonitrile solutions was achieved, allowing the reuse study whose main results were that after four reusing cycles AC reduced its efficiency to remove DIF and IBF in 28 and 34%, respectively. Finally, the effect of ions, such as nitrate, bicarbonate, and sulfate at concentrations commonly found in natural groundwater on the adsorption of both pollutants onto AC was studied using deionized water. As a result, this study suggests considerable interest of AC in real applications due to its versatility and prolonged reuse to effectively remove anti-inflammatory compounds from natural aqueous solution.

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