The Effect of Pistachio Pulp Biochar on the Adsorption of Fluoride in Aqueous Solution

Fluoride is widely used in industries and release to the environment via their effluents. One method of fluoride removal is adsorption using inexpensive adsorbents. The purpose of this sturdy was to compare the efficiency of pistachio pulp biochar in fluoride removal from water.In this study, pistachio pulp biochar was produced through pyrolysis at 600 °C for 3 hours with a heating rate of 25 °C min-1. To determine the adsorption isotherms, 20 mL of fluoride solution with different concentrations (zero, 3, 6 and 9 mg L-1) of NaF salt was added to 0.5 g biochar and then the samples were shaken for 24 hours and finally the adsorption data were fitted to Langmuir, Freundlich and Temkin isotherm models. In order to investigate the effect of time on fluoride adsorption, 20 ml of fluoride solution with initial concentrations of  3, 6 and 9 mg L-1 was added to 0.5 g biochar and samples were shaken for different times (15, 30 , 45, 60, 90,75, 105, 120, 135, 165, 180, 195, 210, 225 and 240 minutes). Then, the concentration of Fluoride was measured. The results showed with increasing the retention time, the percentage of fluoride adsorption by biochar increased and after 240 minutes for concentrations of 3, 6 and 9 mg L-1 were obtained 70.89, 63.05 and 54.66, respectively. The pseudo-first-order and pseudo-second-order models were introduced as the best kinetic models of fluoride adsorption compared to other models. The results of fitting data to the Langmuir, Freundlich and Temkin isotherm models showed that Langmuir model provides a better description of the fluoride adsorption process by biochar. The maximum fluoride adsorption (306 mg kg-1) was obtained by biochar from the Langmuir model.