Iron-modified activated carbon derived from agro-waste for enhanced dye removal from aqueous solutions

Background and aim Finding a cost-effective adsorbent can be an obstacle to large-scale applications of adsorption. This study used an efficient activated carbon adsorbent based on agro-waste for dye removal. Methods Pistachio shells as abundant local agro-wastes were used to prepare activated carbon. Then, it was modified with iron to improve its characteristics. Acid red 14 was used as a model dye in various conditions of adsorption (AR14 concentration 20–150 mg L −1 , pH 3–10, adsorbent dosage 0.1–0.3 g L −1 , and contact time 5–60 min). Results A mesoporous adsorbent was prepared from pistachio shells with 811.57 m 2 g −1 surface area and 0.654 cm 3 g −1 pore volume. Iron modification enhanced the characteristics of activated carbon (surface area by 33.3% and pore volume by 64.1%). Adsorption experiments showed the high effectiveness of iron-modified activated carbon for AR14 removal (>99%, >516 mg g −1 ). The adsorption followed the pseudo-second kinetic model (k = 0.0005 g mg −1 min −1 ) and the Freundlich isotherm model (K f = 152.87, n=4.61). Besides, the reaction occurred spontaneously (ΔG 0 = −36.65 to −41.12 kJ mol −1 ) and was exothermic (ΔH 0 = −41.86 kJ mol −1 and ΔS 0 = −3.34 J mol −1 K −1 ). Conclusion Iron-modified activated carbon derived from pistachio shells could be cost-effective for the treatment of industrial wastewater containing dyes.