Study On Adsorption Of Ni²⁺ By Bamboo Fibers Adsorbent Modified By Citric Acid

With the rapid development of global economy, the water pollution especially heavy metal pollution in global world is becoming an increasingly severe problem. Among the current wastewater treatment method of heavy metal, the traditional removing method of physical and chemistry had been replaced by innovative biological treatment method which is the major research direction. In the perspective of the waste recycling, reused the resource of wasting bamboo, successfully made a sort of cellulose adsorbent with low cost and simple process, which was prepared in two-stage modification by citric acid. Specific research contents and results are as follows.(1)Three kinds of catalyst have been evaluated and the influence of six factors include concentration of pretreatment solution, pretreatment time, CA/bamboo amount ratio, catalysts/bamboo weight ratio, reaction temperature, reaction time on modification were researched. Results showed that the optimum conditions were 5% pretreatment solution concentration, 180 min of pretreatment time, 20mmol/g of CA/bamboo amount ratio, 40 wt% sodium hypophosphite, 90 min of reaction time, 120℃reaction temperature. The products under the above conditions showed increased significantly adsorption capacity that the carboxyl group content and the maximum adsorption capacity were up to 3.373mmol/g, 9.486mg/g, respectively.(2)Through the adsorption experiment of single factor, the results showed that the optimum pH was 8.5, the economical amount of adsorbent was 0.2g in 100 m L solution which concentration is 20mg/L and the optimum temperature was 30℃. The research of kinetic and thermodynamic showed that the adsorption process of modified bamboo fiber was more conformed to the pseudo-second-order model and the Langmuir isotherm. The Box-Behken experiment results showed that the fitted model had significant level, temperature and adsorption were significant factor, and there was interaction on removal effect between pH and temperature. The optimum adsorption condition predicted by model was pH at 8.57, 9.13 hour of adsorption time, 22.94℃adsorption temperature. Under above condition, the predicted removal rate will be 88.80% which was much closed the real number, 87.83%.(3)Compared two desorption agents in desorption experiment, it found out that HCl showed great desorption performance and the optimum concentration was 0.15mol/L, but desorption effect of EDTA was not good as HCl. After the research on desorption temperature, it showed that desorption effect was positive with temperature and the optimum desorption temperature was 50℃. The regeneration rate of modified bamboo fiber could maintain above 90% and adsorption capacity declined 1.65mg/g after several desorption-adsorption experiment, it meant that modified bamboo fiber had great regeneration property and relatively long using time.