Preparation And Characterization Of Novel Materials For Adsorption Of Copper Or Uranyl Ions

The continuous development of industry exaggerates the problem of water pollution which contains heavy metals seriously.Copper-containing wastewater and uranium-containing wastewater are two kinds of common heavy metal wastewater,which are harmful for human being and environment.Therefore,it is urgent to seek effective methods to remove Cu²⁺and UO₂²⁺from water.Among several methods of treating wastewater containing heavy metals,adsorption method is widely used because of its advantages such as simple operation and extensive absorbents.The key point of adsorption method is the adsorbent.Conventional adsorbents are difficult to be recycled or have low adsorption efficiency.Therefore,two novel adsorbents are prepared and their adsorption processes for Cu²⁺or UO₂²⁺in water are also studied.The details are as following:（1）Sulfonated polyimide（SPI）membrane with good adsorption property for Cu²⁺and excellent recycling was prepared by using 1,4,5,8-naphthalenetetra-carboxylic dianhydride（NTDA）,4,4′-diamino-biphenyl 2,2′-disulphonic acid（BDSA）,4,4′-oxydianiline（ODA）and 2-（4-aminophenyl）-5-aminobenzimidazole（APABI）.The maximum adsorption capacity is 23.46 mg g^-1 and the removal rate is 58.65%under the optimum adsorption conditions(The pH value is 4.7,the adsorption time is 2 h,the initial concentration is 40 mg L^-1,and the adsorption temperature is 25?C).The adsorption process agrees well with the pseudo-second-order kinetic model and Langmuir isothermal adsorption model.The elution rate can reach 90.0%by using H₂SO₄ as an elution solution,and the adsorbent can be used for several times.（2）The carboxylated eggshell membrane（ESM-COOH）that has excellent adsorbing UO₂²⁺property was prepared by modifying ESM with glyoxylic acid.The content of carboxyl group of ESM-COOH was measured by Boehm titration method.Besides,the optimum modification time is determined to be 15 h in terms of the adsorption capacity,and the adsorbent is marked as ESM-COOH-15.The optimum adsorption conditions are as following:the ratio of solid to liquid is 0.1 g L^-1,the adsorption time is 16 h,the initial concentration is 40 mg L^-1,the pH value is 6.0,and the adsorption temperature is 75?C.The maximum adsorption capacity of ESM-COOH-15 is 224.14mg g^-1 in these optimum conditions.The adsorption process agrees well with pseudo-second-order kinetic model and Langmuir isotherm adsorption model.In addition,the adsorption of ESM-COOH-15 for UO₂²⁺is promoted with increase of ionic strength.The elution rate can reach 99%by using 0.5 mol L^-1 HNO₃ as an elution solution.At the same time,the adsorption capacities are almost constant when the adsorption-desorption process is repeated for five times.These results show that the ESM-COOH-15 has a good reusability during the process of UO₂²⁺adsorption in wastewater.