Preparation Of New Chelating Fiber As Adsorbent For Fast Removal Of Cu²⁺ And Ni²⁺ From Water

Many water pollution accidents occurred in China every year, and these accidents not only destroyed the ecological environment, but also cause enormous economic losses. Compared with ordinary water pollution, heavy metal pollution accidents could cause great more damages for uncertainly characteristics. So once the pollutants enter the water, it could spread rapidly, and caused a wider range of environment damage. Different from the conventional control of heavy metal water pollution, a qualified method which could be used in disposal of water pollution incidents should be fulfilled following requirements:1) could remove the pollutants from water in a short time;2)handle easily. The current disposition technology of heavy metal water pollution accidents included coagulation/precipitation, chemical oxidation/degradation and activated carbon adsorption. But there were some deficiencies in the actual application process。In this paper, a new fibrous adsorbent was prepared for fast removal of Cu2+and Ni2+from water. Its adsorption capacity was investigated and used commercial ion-exchange fiber as reference. The effects of pH, temperature, calcium ion and natural organic matter on adsorption were also investigated, which could provide a technical support in the practical disposal of heavy metal water pollution accidents. The main research contents and conclusions were shown as follows:(1) A new fibrous adsorbent was synthesized with PET by grafting and modification. This new fibrous adsorbent was characterized by FT-IR and CNMR. The result indicated that the best temperature for grafted polymerization reaction was80℃, acrylic acid concentration was10%, sodium carbonate concentration was2g/L, within4hours’reaction, the fiber had a high rate of graft。 This fibrous adsorbent with amine and amide based on surface was hydrophilic and tenacious.(2) Comparing with commercial ion-exchange fiber, new fibrous adsorbent had higher adsorption rate and capacity for Cu2+and Ni2+. The chelating interaction between fiber’s amino groups and heavy metal ions were mainly adsorption force. Langmuir model could fit the adsorption isotherms well, and pseudo second order equation could describe the adsorption kinetic curves. The absolute value of enthalpy changes (△H) indicated that adsorption of Cu2+and Ni2+was an endothermic process. The negative values of AG for Cu2+and Ni2+removal with new fibrous adsorbent indicated that the adsorption reaction was a spontaneous process, and the positive values of AS indicated that the adsorption reaction was propelled by the entropy.(3) The effects of calcium ions, organic matter, pH value, temperature on adsorption were systematically investigated. The new fibrous adsorbent could fast remove heavy metal ions from water effectively in the presence of calcium ions and natural organic matter. But as the calcium ion concentration increased, the fiber’s adsorption capacity for Ni2+declined. The higher uptake capacity of Cu2+and Ni2+by new fibrous adsorbent was achieved at higher pH values, and the lower uptake capacity of Cu2+and Ni2+was observed in an acidic medium. The removal of heavy metal ions increased when temperature increased.