Preparation And Study Of Heavy Metal Adsorbent From Acylated Cellulose

Cellulose is the most abundant and renewable biopolymer in nature,and it has a certain absorption capacity but the capacity is limit.So we should modify cellulose to improve its adsorption capacity.Cellulose molecule contain a large number of hydroxyl which provides the possibility for chemical modification of cellulose.How to modify cellulose makes it to be a biological adsorbent which has a stable performance and strong adsorption capacity has become a hot spot.In this work,we have discussed two methods of synthesis of cellulose based heavy metal adsorbent,and the mechanism of modification was also been discussed.The physical properties of our adsorbent were characterized by the modern analytical testing,and the adsorption performance was studied.Firstly,the cellulose was used as the substrate,and the acylated cellulose?SMC?was prepared by a reaction with succinic anhydride in the presence of toluene/triethylamine and a 4-dimethylaminopyridine catalyst.Secondly,SMC was reacted with Fe?III?or triethylenetetramine to obtain two heavy metal adsorbents.SMC reacted with FeCl₃ solution to obtain Fe-loaded adsorbent?ISMC?,and the mechanism of its synthesis was analyzed.The L9 orthogonal experiment was designed to obtain the optimal synthesis reaction parameters which were pH=6,T=35 ?,t=24 h,and n?Fe????: n?carboxyl?= 4.And the reaction temperature is the most important influence factor.The results of FTIR and EDS illustrated that the modification of cellulose was successful.Amine-based adsorbents?TSMC,CSMC,DSMC?were prepared by a reaction with triethylenetetramine in the presence of DMF and a activator.And the result of FTIR demonstrated the modification was successful.We had explored the adsorption performance for heavy metal of two adsorbents.In the experiment of the adsorption of Cr???onto ISMC,the results showed that the adsorption capacity is greater at lower pH,and the optimum pH = 2.The behavior of Cr???adsorbed onto ISMC followed the pseudo-second order kinetic model.And the adsorption obeyed the Langmuir adsorption isotherm model.In addition,we also conducted experiments of the regeneration of adsorbent.The result showed that ISMC had a good desorption effect?> 95%?.After four desorption/adsorption cycle,the adsorption capacity was reduced by 16%.Among TSMC,CSMC and DSMC,TSMC had the best adsorption capacity of Cu²⁺ and Pb²⁺.Therefore,we selected TSMC as the adsorbent to remove Cu²⁺ and Pb²⁺ from solution.The result showed that the adsorption capacity increased with the increase of pH and the optimum pH was 6.In addition,the removal efficiency increased as the adsorbents amount increased.Moreover,the temperature of solution had a great influence on adsorption effect.The adsorption capacity changed significantly with the change of temperature.When the temperature increased from 288 K to 308 K,the adsorption capacity for Cu²⁺ and Pb²⁺ were increased from 95 mg·g^-1 and 149.4 mg·g^-1 to 178.7 mg·g^-1 and 188 mg·g^-1,respectively.At the same time,the removal efficiency increased from 47.6% and 73.1 to 89.4% and 94%,respectively.The adsorption behavior followed the pseudo-second order kinetic model and Langmuir isotherm model.And the calculated qmax for Cu²⁺ and Pb²⁺ were 103.8 mg·g^-1 and 228.3mg·g^-1,respectively.The adsorption mechanism were ion exchange and coordination process.The desorption and regeneration of adsorbent was performed in 0.2 mol·L^-1 HCl solution.Result showed that TSMC has a good desorption effect?> 89%?.After four desorption/adsorption cycle,the adsorption effect was reduced by 21%.