Carboxymethyl Chitosan-Bentonite Composite Adsorbent Deal With Heavy Metal

Heavy metal pollution could gradually become severer and severer with the accumulation of heavy metal ions since heavy metal contamination could not be degraded in natural environment. Therefore, the method research of disposing the heavy metal waste water becomes a heated research aspect at present. With the increasing of the waste water discharge standard by country, heavy metal waste water treatment technology of low concentration is gaining increasing interest. In numerous methods of treating heavy metal waste water, it was considered to be an economy, practical and effective method that utilizing friendly environmental materials to adsorb and deal with the heavy metal ions. Combined with the efficient adsorption ability of carboxymethyl chitosan for heavy metal and the strong adsorption ability of bentonite in wastewater treatment, a new composite adsorbent of carboxymethyl chitosan intercalated bentonite was prepared in this topic research. The physicchemical properties of this composite adsorbent and the parameters in the process of adsorbing low concentration heavy metal ions were investigated systematically.The experimental results were shown as follow:(1) the adsorption of compound adsorbent to Ni2+was fast, and easy to reach adsorption equilibrium, while the adsorbent to Cu2+and Cr3+taken30min and180min.(2) The adsorption of Cu2+、Ni2+、Cr3+fits Langmuir isotherm. The adsorption dynamoics follows second-order kinetics reaction. The rate of adsorption to Ni2+is most fast, while to Cu2+is second, and to Cr3+is the slowest.(3) ΔG, ΔH and ΔS for three types of metal in different temperature were calculated, it was confirmed that the adsorption of three kinds of metal exhibited spontaneous as ΔG was negative. ΔH of Cu2+、Ni2+was negative, so that the adsorption process was exothermic. ΔH of Cr3+was positive, the adsorption process was decalescence.(4) Response surface and contour line analysis shows that the influence of pH value on the adsorption capacity of carboxymethyl chitosan-bentonite composite absorbent to Cu2+was stronger while adsorption time is the second, and initial concentration is less. And the optimal adsorption condition of the compound adsorbent to Cu2+were pH4, initial concentration33.00mg/L, adsorption time25.00min.(5)Composite adsorbents adsorb to mixed system in the condition of temperature25℃, pH4and the adsorption time180min, the total baekho Moore number of heavy metal ions adsorbed increased than single components system, but each ion adsorption capacity decreased compared with single component system.(6)HNO3and EDTA solution could be used as eluting agents for carboxymethyl chitosan-bentonite composite absorbent adsorbing Cu2+. The regeneration effect of EDTA is better than HNO3.