| This paper studies the preparation of porous cross-linked chitosan resin and itsadsorption characteristics of phosphate in water samples. The porous cross-linkedchitosan resins were produced by using anti-phase suspension cross-linking technique;which includes amino-protecting, cross-linking effect and by releasing the adsorptionsites afterwards. Chitosan was chosen as raw material, xylene as dispersant,benzaldehyde as amino-protective agent, epichlorohydrin as crosslinking agent, ethylacetate as the pore agent.The orthogonal experiment method was used to discuss the influence on resin porestructure characteristics when different dosages of amino protective agent, cross-linkingagent and pore agent were added to the reaction liquid. The results showed that thedosage of the cross-linking agent had the greatest influence on pore structure. With anincrease dosage of cross-linking agent, resin pore volume showed a trend of decreaseafter the first increase. When the dosage of cross-linking agent was0.9ml, the porevolume could reach the maximum0.5652ml/g. The experiment of pore agent showed asimilar result but the pore agent gave a less effect on the resin pore structure. Generally,when the dosage of pore agent increased, the pore volume increased as well. When thepore agent reached5ml, the pore volume has maximum value. Amino protective agentalso has certain influence on pore structure, when the dosage is4ml, the volume reachedthe maximum value. The water/oil ratio and stirring speed were studied on the particlesize; the results showed that, when water oil ratio was2:3and the stirring speed is300r/min, the resin particle size is most suitable for requirement of adsorption experiment.A series of characterization were made for the cross-linked chitosan resin: Infraredspectrum analysis was used to track each step in the synthesis process of the resin, andproved the existence of the cross-linking reaction as well as the formation and removalof Schiff base; Scanning electron microscopy (SEM) was used in the comparison testsbetween resins with pore agent or not. The result showed that the resin with pore agenthad porous structure and particle size was larger, which proved that the pore resin wasimportant in the preparation. Furthermore, thermal stability analysis showed thatcross-linked chitosan resin had a good stability under119.83℃.In the static adsorption experiment, the influence of pH, particle, particle size,temperature, time and interfering ions on the adsorption quantity were studied. The influence of pH on the adsorption rate showed that, along with the increase of pH, theadsorption decreased after the first increase; when pH=3, the optimal phosphorusremoval rate could reach85.3%. In the condition that particle sizes were0.28-035mm,the adsorption rate reached maximum; The Adsorption kinetics studies indicated that theadsorption equilibrium quantity increased along with the rise of temperature. At60℃,the maximum amount of adsorption was0.69mg/g. The adsorption process was inaccordance with the pseudo-second order kinetic model. The study on adsorptionthermodynamics showed that the adsorption process was in line with the Langmuiradsorption model, and the adsorption was an endothermic, spontaneous,entropy-increasing process, where the adsorption rate increases along with thetemperature. The results of activation energy showed that the control factor of theadsorption rate was the within ion diffusion.The recovery characteristics of the resin indicated that the resin had good recoveryeffect when using two-step processing with HCl solution and NaOH solution. Cycleperformance study showed that the cycle performance of the resin was good. |
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