Study on Adsorption of Heavy Metal Ions in Aqueous Solution by a New Type of TCAS-adsorbed Resin

The freshwater resources are abundant in China, because of its large population, the per capita share of water resources is far below the world average. And China was listed as one of the 13 countries which lack of water resources per capita in world. In the condition of shortage of water resources, the waste and pollution of water resources are very serious. According to the survey, China has more than 1/3 of the rivers have been contaminated, nearly 50% of the important urban water sources do not conforming to drinking water standards, and more than 90% of the urban water were pollution. According to "Chinese Environmental Situation Communique in 2006"in 2006, the wastewater emissions from industrial in China is two hundred and four billion tons, 44.7% of total wastewater emissions which is the main source of environmental pollution. The toxicity of heavy metals is serious. Heavy metals can not be metabolized easily; they also have bioconcentration and biomagnification, so heavy metals are threat to human and aquatic organisms seriously. Therefore, studying how to remove heavy metal pollutants in water effectively is an important issue in water treatment technology currently.Calixarene is the third generation supramolecular compound which has a development potential, it can complex with heavy metal ions. Contraposing the inadequacy of the existing adsorbents, a new type of TCAS-adsorbed resin had been prepared by loading an anion-exchange resin with the active component named thiacalix[4]arenetetrasulfonate （TCAS）. TCAS-adsorbed resin and its intermediate product were characterized by the means of IR spectrum, UV spectrum, ESI-MS and ¹H-NMR. Through the static tests, the capacity of the new TCAS-adsorbed resin to remove of Cd²⁺ andCu²⁺ was investigated, and the main mechanism of adsorption was also discussed.The experimental results showed that, the electrostatic force between TCAS and anion exchange resin was stable and this made TCAS-adsorbed resin more stable in aqueous solution. The static adsorbent tests revealed a high adsorption ability of the TCAS-adsorbded resin toward heavy metals. The maximum adsorption capacities of the TCAS-adsorbed resin toward Cd²⁺ and Cu²⁺ was 14.45 mg/g and 26.32 mg/g . When several heavy metal ions coexisted in the aqueous solution, the adsorption of heavy metals was favorable in the order Cu²⁺>Zn²⁺>Cd²⁺>Pb²⁺. Within the range of experimental concentration, the removal rate of heavy metal ions would increase as the dosages of TCAS-adsorbed resin increasing, the equilibrium time would increase as the temperature increasing. When the reaction temperature was in the range of 10-30℃, low temperature was benefit for TCAS-adsorbed resin to adsorb heavy metal ions. When the concentration of heavy metal ions were equilibrium in aqueous solution, the concentration could reach the national emission standards. When the pH was neutral or alkaline, the removal rate of TCAS-adsorbed resin towards Cd²⁺ was high, while the pH value did not have an important effect on the adsorption of Cu²⁺. The isothermal adsorption of TCAS-adsorbed resin for heavy metal ions fit Langmuir equation. The adsorption rate fit second-order rate equation. TCAS-adsorbed resin did not adsorb Ca²⁺and Mg²⁺, and the existence of Ca²⁺ and Mg²⁺ in aqueous solution had no effect for TCAS-adsorbed resin to adsorb heavy metal ions. The adsorption metal ions could be recovered while TCAS-adsorbed resin could be reused. The complexation was the main mechanism for TCAS to adsorb heavy metal ions.