Valorization of pistachio bark as the biosorbent for adsorption of dye and heavy metal ions from the contaminated water

This work presents the results of the experimental study for the pyrolysis of biomass of pistachio hard bark (P.B.) and the ability of the produced biochar for adsorption of various contaminants. The reported experiments aimed to register the yields of pyrolysis products by using different catalysts and activation methods. The highest yield of biochar is about 42W% obtained by using Fe catalyst with H₃PO₄ chemical activation process, and the lowest yield of the produced biochar is about 27 W% produced by catalytic pyrolysis with fly ash catalyst. The produced biochars were characterized by XRD, SEM–EDX, and FTIR analysis methods, and they were used for the adsorption of methylene blue, methyl orange, chromate, and cadmium ions with the removal efficiencies of about 0.98, 0.96, 0.95, and 0.94%. NaOH-activated P.B. pyrolyzed with iron catalyst shows the highest adsorption capacities of 19 and 300 mg/g for the adsorption of methylene blue and cadmium ions. However, H₃PO₄ chemical-activated P.B. was the best adsorbent of methyl orange with a maximum adsorption capacity of 10 mg/g, and P.B. pyrolyzed with iron catalyst and impregnated with potassium permanganate shows the highest adsorption capacity of 72 mg/g for chromate ions. Further, isotherm modeling was carried out using Langmuir and Freundlich models. The adsorptions of methylene blue, methyl orange, and cadmium ions were relatively better fitted with the Langmuir model with the R² values higher than 97%, but the adsorption isotherm of chromate ions could be well-presented by the Freundlich model with the R² values higher than 92%.