Characterization of novel adsorbents from Phoenix dactylifera rachis. Box–Behnken design, kinetic, and isotherm models for BEZAKTIV Red S-MAX dye adsorption onto the produced carbons

The objective of this work was to characterize the produced activated carbons based on Phoenix dactylifera rachis (date palm rachis: RP) using steam with different burn-off values (45, 55, and 65%), and then use those carbons to eliminate BEZAKTIV Red S-MAX (RS), a commercial textile dye. The characterization of the carbons was carried out by analyzing N 2 adsorption–desorption, SEM, FTIR, TGA/SM, Boehm titration, and pH PZC . The specific surface area S 2D-NLDFT was 500, 646, and 507 m 2 /g for the activated carbons PRAC45, PRAC55, and PRAC65, respectively. The Box–Behnken design (BBD) of experiments was applied to determine the influence of burn-off (A), initial concentration (B), and pH of the solution (C) for the RS dye elimination from the aqueous system. The significant interactions between the factors were AB and BC with p -value < 0.05. The RS dye adsorption experiments were examined by applying the kinetic and isotherm models and by studying temperature and pH effect. It was found that the RS adsorption followed the pseudo-second-order ( R 2 > 0.99) and the removal data were well fitted to the Langmuir isotherm model. The Langmuir maximum adsorption capacity Q m of RS dye was 198 mg/g for PRAC55. The regeneration of the carbons using thermal treatment was tested, and it revealed that the specific surface area S 2D-NLDFT and the RS adsorption capacity Q m increased after the regeneration to 965 m 2 /g and 56.3 mg/g, respectively, for PRAC55. The Phoenix dactylifera rachis adsorbents could eliminate industrial wastewater (IW) which contains BEZAKTIV dyes with an adsorption rate superior to 55%. Graphical abstract