Performance Evaluation of Tannic Acid Removal by Nano Polyamidoamine Dendrimer from Aqueous Solution

Tannic acid (TA) is a polyphenolic compound which is categorized in dissolved organic matter (DOM) classification. This matter has toxicity for aquatic organism, such as fish, phytoplankton, algae and invertebrates. TA is an anionic organic matter and its molecular weight is 1700 g/mol. This compound contributes to the production of disinfection by products (DBPs) during chlorination process in water treatment. Thus, it is significant to remove tannic acid from environment in terms of human health and environment. In this study, the performance of nano polyamidoamine-G7 (PAMAM-G7) dendrimer in removal of tannic acid from aqueous solution was investigated. Polyamidoamine dendrimer (PAMAM) with ethylene diamine core synthesized by the Tomalia method. Then, the adsorbent was characterized by Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). The effect of various experimental parameters such as pH solution, adsorbent dosage, contact time and temperature was evaluated. The concentration of tannic acid was determined at 278 nm by UV-VIS spectrophotometer. The adsorption of TA has been studied in term of pseudo-first and second-order kinetics, thermodynamic parameters (Delta G degrees, Delta S degrees and Delta H degrees), Langmuir and Freundlich isotherms models. The results showed in optimized conditions (pH 7, TA concentration = 5 mg/L, shaking = 200 rpm, adsorbent dose = 0.005 g/L, temperature = 25 degrees C) maximum adsorption capacity and removal efficiency of TA were 38.02 mg/g and 98.83%, respectively. The adsorption kinetics of TA onto PAMAM-G7 followed a pseudo-second-order model (controlled by chemical process) and it is well described by Langmuir adsorption model (R-2 = 0.9076). The adsorption TA capacity for PAMAM-G7 increased with increasing TA concentration and electrostatic force and hydrogen bonding helps to adsorb the TA molecules on adsorbent. The calculated thermodynamic parameters showed that TA adsorption onto PAMAM-G7 was endothermic and spontaneous (Delta S degrees = 0.263, Delta H degrees = 70.96 and Delta G degrees = -7.428 at 25 degrees C). Thus, PAMAM-G7 can be an appropriate adsorbent for removal of tannic acid from aqueous solution.