Removal of diclofenac and ibuprofen on mesoporous activated carbon from agro-industrial wastes prepared by optimized synthesis employing a central composite design

Abstract

Synthesis of biochar from sunflower seed shells by using H3PO4 (AC-H) and NaOH (AC-N) as activated agents was optimized through a central composite design (CD) for building a second-order (quadratic) model with factorial points 2 k (k = 2) where concentration of activating agent (20–80% wt.) and carbonization temperature (300–600 °C under N2 atmosphere) were used as variables. At optimized conditions suggested by the experimental design for AC-H (H3PO4 at 80% wt. and annealed at 544 °C) and AC-N (NaOH at 50% wt., and annealed at 300 °C), materials exhibited the highest specific surface area (SBET), mesoporosity (Smeso), and methylene blue (MB) adsorption. AC-H exhibited several surface functional groups such as -P2O7, and -COOH as well as high porosity and acidity caused by the H3PO4 treatment. Regarding diclofenac (DIC) and ibuprofen (IBU) adsorptions, AC-H and AC-N exhibited maximum adsorption capacities of 690.2 and 105.7 mg g−1 and 23.6 and 4.5 mg g−1, respectively. The novelty of this study lies in the combined use of an experiment design procedure and exhaustive physicochemical characterization to find the best synthesis conditions of biochars exhibiting high specific surface area, mesoporosity, and a diversity of surface functional groups to be applied in the removal of pharmaceutical pollutants in water.