Study on the Structure and Properties of Cadmium Removal Adsorbent Made by Ultrafine Silica Powder

An efficient and recyclable cadmium removal adsorbent was prepared by molding and sintering of ultrafine silica powder produced from ferroalloy plant as the main raw materials, with the addition of a certain amount of AI（OH）3 and CaO for modification. XRD and SEM were used to characterize the crystal phases and microstructures of the adsorbent. The influences of different pH, initial cadmium concentration and contacting time on the cadmium adsorption capacity were investigated. The results show that the cadmium removal capacity is up to 0.239 mg/g at the initial Cd2＋ concentration of 5 g/L, pH value of 7 and contacting time of 120 rain when the optimum, mass ratio is 70（ultrafine silica powder）：30（Al（OH）3 and CaO mixture）. The corresponding adsorbent has a porous structure with main crystalline phases of CazAI2SiO7 and CaSiO3. Cadmium is adsorbed and removed mainly by physical adsorption, assisted by chemical adsorption.

Purification of Starch from Cadmium-Contaminated Rice and Development of Functional Recombinant Rice

In order to provide a new utilization method for cadmium-contaminated rice,a preliminary study of the removal of rice starch cadmium by water,calcium hydroxide,sodium hydroxide and citric acid was conducted,the damage degree of starch was compared by SEM,and then the recombinant rice was obtained by a twin-screw extruder using the starch which met the safety standard.The physical and chemical properties of recombinant rice were analyzed by acid hydrolysis and texture analyzer.The results showed that citric acid was a good rice cadmium removal agent.The quality of recombinant rice prepared from cadmium-removed rice starch was improved;the acid resistance was increased.Heavy metal contaminated rice can be a staple food with better quality and higher value through processing.

Cd(Ⅱ)removal from phenols-bearing wastewater using magnetic carbon nanotubes

This project studied Cd(Ⅱ)uptake from phenols-bearing wastewater using magnetic carbon nanotubes(MCNT)as adsorbent.Initially,Cd(Ⅱ)complexation with various phenols was confirmed by FT-IR spectroscopy.Factors affecting Cd removal are:solution pH;type of phenol[phenol(Ph),2-chlorophenol(2-CP),2-nitrophenol(2-NP),and 2,4-dinitrophenol(2,4-DNP)];Mag:CNT mass ratio;Cd:phenolic compound molar ratio;and the effect of order of adding adsorption components(MCNT,Cd(Ⅱ),phenolic compound)to the extraction medium.It was found that the presence of phenols in the extraction medium caused a 10e50%decrease in Cd(Ⅱ)uptake.This was probably due to a competition between phenols/surface functional groups towards Cd(Ⅱ);or phenols/Cd(Ⅱ)to occupy the surface functional groups.2,4-DNP was selected as a model phenolic compound.The optimum adsorption conditions[1:1 M ratio of(Cd(Ⅱ):2,4-DNP)at pH 6 using MCNT(1:1)adsorbent]resulted in adsorption capacity of 17.9 mg Cd g^(-1).The best order of adding reagents was(Cd(Ⅱ)þMCNT(1:1))and then 2,4-DNP.The regeneration of the adsorbent was possible by using 0.5 M HNO_(3)where 90%of adsorption efficiency was reserved after three times of successive use.Upon presence of co-existing ions,75%of the adsorption efficiency was maintained.The applicability of the proposed adsorption method on real water samples was evaluated.