Synthesis of tris(hydroxymethyl)aminomethane modified polystyrene based polymeric sorbent and removal of boron from aqueous solutions

Boron is placed in-group 13 of periodic table and found at low concentration in a wide area range such as rock, soil and water in nature. Boron is used in many industrial applications, especially in insulation, retardant fiberglass and ceramic industry. In addition, boron is an essential element for living organism systems. Excess amount of it causes water and other environmental pollution. As high concentration causes adverse effects, boron level is limited in irrigation or drinking water. The World Health Organization (WHO) currently recommends the concentration of boron in drinking water to be 2.4 mg/L. Consequently, boron removal from wastewater is an important topic. Various removal methods are available for boron separation. Some of them are; precipitation-coagulation, solvent extraction, membrane filtration, reverse osmosis, electro dialysis and adsorption. Adsorption is completely different from others because it is a very useful method and needs low price equipment for removal of boron from wastewater. In the first part of this study, tris(hydroxymethyl)aminomethane was interacted with poly(vinyl benzyl chloride) resin to obtain boron selective sorbent. The resin was characterized with FT-IR spectroscopy to determine the functional groups important for boron sensitivity. Total amine content of the resin was calculated analytically as 2.45 mmol.g-1 sorbent. In the second part of the study, experimental measurements were performed on modified resin about boron adsorption. Adsorption capacity of the sorbent was investigated for different boron concentrations. Boron loading capacity of the sorbent is 2.17 mmol.g-1 resin, in non-buffered conditions. Sorption behavior was also observed in the presence of different concentration foreign ions such as Ca+2 and Mg+2. Besides that, boron adsorption was further studied at varying pH in the range of 2.0-10.0. Kinetics of boron sorption was performed at low concentration to investigate the efficiency of the modified resin at this condition. For this purpose, pseudo-first order, pseudo-second order and intraparticular diffusion kinetics models were used. Regeneration of the loaded resin was also studied. 2.10 mmol.g-1 boric acid was recovered of the loaded sample, which showed that the resin was able to desorp nearly completely.