Preparation And Adsorption Mechanism Of Tannins Chelating Resin Through Inverse-suspension Polymerization

Based on reviewing the present researches of chelating resin and the functional polymers of plant tannins,using black wattle tannins and paraform aldehyde in fluid-wax as organic dispersant, a spherical tannin chelating resins was prepared through inverse-suspension polymerization. The condition of reaction was determined by means of orthognonal experiment.The optimal condition of synthesis was: The distributing of particle size 20mm;milling rotate speed 450r/min;m (tannins): m (paraform aldehyde) =12:1; reaction temperature 67℃; reaction time 3.5 h; fluid-wax volume 65 mL;The best static state adsorption condition of tannins chelating resins: the time is 9h, the incipient concentration is 100mg/L, the adsorption temperature is 25℃, the adding quantity of resins is 0.1g, the pH is invariability;The best desorption experimental condition:the desorption agent is ethanol, the desorption temperature is 45℃, the adsorption rate is above 95%.The experiment studied adsorption effect of tannins chelating resins towards Cr⁶⁺,Cu²⁺and the results indicate that tannins chelating resins has better adsorption effect towards Cu²⁺ than Cr⁶⁺, which may be contributed to the phenolic hydroxyl group of the adsorbent. In addition, easily desorption of tannins chelating resins was showed in experiments and exhibits excellent reuseability.The structure of adsorption products was characterized by FIR, XRD, TG, DSC and SEM. The studies on the thermodynamics and the kinetics showed that the adsorption of Cr6+,Cu2+ onto tannins chelating resins is the endothermic sorption process and occurs automatically. Freundlich isotherm is suggested as the propriate type for this procedure. Furthermore, the adsorption propelling force was mainly the coordination-bonding interaction between Cr6+,Cu2+ and the–OH of tannin chelating resins. The studies on the kinetics and reaction activation energy showed that both film diffusion and particle diffusion are the rate-controlling process in the adsorption system tested. But particle diffusion is more predominant.