Adsorptive removal of cypermethrin from aqueous solution on activated carbon derived from tobacco stem wastes: equilibrium and kinetic studies.

Pesticides are pollutants found in wastewater as a result of agricultural activities. The adsorption process is a cost-effective technique among the other treatment processes because of its simplicity in design, easy operation, and high adsorption capacity for the removal of pesticides from wastewater. Activated carbon (AC) is a widely used adsorbent but due to its high production cost, its use is limited. This limitation has necessitated a growing interest in alternative sources in the production of low-cost activated carbon from agricultural wastes and other waste materials. In the present study, activated carbon produced from tobacco stems via chemical activation using phosphoric acid was tested for the removal of cypermethrin from aqueous solution. Prior to its use, the prepared activated carbon was characterized by FTIR and SEM. Tobacco stem-activated carbon with an impregnation ratio of 1:3 produced at a temperature of 600 °C was used in bench studies on the removal of cypermethrin from aqueous solutions because of its high iodine number of 776.25 mg/g and fixed carbon content of 85.33%. Batch experiments were performed to determine the optimum adsorption conditions, and suitable kinetic for the adsorption of cypermethrin onto tobacco stems activated carbon (TAC). The influence of adsorbent dosage, contact time, and initial cypermethrin concentration were studied. High-Performance Liquid Chromatography (HPLC) was used for the determination of cypermethrin concentration and a recovery percentage of up to 99.0% was obtained from a spiked concentration of 200 ppm. Equilibrium data were obtained by testing the adsorption data using the Langmuir and Freundlich models. The results obtained from the isotherm and kinetic study are best described using the Freundlich isotherms and pseudo-second-order kinetic adsorption models with the highest regression coefficients' of R2 = 0.9998 and 0.9937, respectively. Results showed that the maximum amount of cypermethrin adsorbed was 2.162 mg/g and this was achieved at 270 min of the contact time. A comparison of the prepared TAC and a commercial activated carbon (1105 m2/g, pore diameter of 1.67 nm, and micropore volume of 0.4004 cm3/g) demonstrated to have a remarkable potential for removing cypermethrin pesticide from aqueous solution. This facile route highlights the possibility of utilizing tobacco stems to produce low-cost, green, and effective activated carbon for the removal of cypermethrin from water, thus, converting the waste to a value-added product as well as providing some solutions to the many challenges faced with tobacco stem wastes disposal. The work not only offers an economic source for the production of activated carbon but also demonstrates that TAC is a promising adsorbent for the removal of cypermethrin and other organic pollutants from wastewater. [ABSTRACT FROM AUTHOR]