Preparation And Research On Granular Adsorbent Of Chitosan-based Material And Adsorption Capacity For Pb(Ⅱ)

Chitosan used as a matrix material,three kinds of granular adsorbents for adsorbing Pb(Ⅱ)ion from the wastewater solution were prepared via the condensation reaction of Schiff base and the condensation reaction of hydroxyl and carboxyl groups,respectively.Meanwhile the adsorption performance and adsorption mechanisms were also studied.The primary research details were as follows.p-Phthalaldehyde,2-aminophenol and graphene oxide were used as raw materials to modify chitosan.Three different kinds of granular adsorbents CS-HPIMB,GO-CS and GOCSB were prepared,and they have the advantages of high adsorption capacity,simple separation method and repeated recyle use.Their structures were characterized,and then the effects of p H,contact time,amount of adsorbent and initial concentration of lead ion on the adsorption of Pb(Ⅱ)ion were also studied,respectively.The results indicated that the optimum p H value for the three adsorbents are all 5.0.The adsorption of CS-HPIMB is at an equilibrium at a contact time of 240 min.On the other hand,the contact time of adsorption equilibrium of both GO-CS and GO-CSB are180 min.As for the effects of adsorbent dosage,the best amount of CS-HPIMB,GO-CS and GO-CSB are 1.20,1.40 and 1.00 g/L,respectively.Finally,the best initial concentration of Pb(Ⅱ)ion adsorbed by CS-HPIMB,GO-CS and GO-CSB are 300,500 and 600 ppm,respectively.Under the above conditions,their adsorption capacities are 123.05,173.72 and198.01 mg/g,respectively.The adsorption kinetics for the three adsorbents in adsorbing Pb(Ⅱ)ion from the wastewater solutions were conformed to the pseudo second-order ones.The results showed that there were chemical adsorptions in the adsorption process besides physical adsortions,and the chemical adsorption rate was controlled by the chemical reaction rate.The adsorption isotherm kinetic study indicated that the adsorption process for CS-HPIMB was more in line with the Freundlich adsorption isotherm model,which revealed that the adsorption active sites of CS-HPIMB were non-uniformly distributed.While the Langmuir adsorption isotherm model was effective on the adsorption process for GO-CS and GOCSB.This revealed that the adsorption of Pb(Ⅱ)ion by those two adsorbents were mainly monomolecular layer adsorption.In addition,the theoretical maximum adsorption capacities of CS-HPIMB,GO-CS and GO-CSB for Pb(Ⅱ)ion were obtained by calculating and fitting the data,and they were calculated as 162.66,181.82 and 217.39 mg/g,respectively.Finally,after 5 adsorption-desorption cycles,the adsorption capacities for CS-HPIMB,GO-CS and GO-CSB were reduced to 44%,68% and 58% to the initial adsorption capacity value,respectively.The researches proved that the three different kinds of chitosan-based granular adsorbents can effectively remove Pb(Ⅱ)ion from the contaminated water.Consequently,they have potential applications in the field of Pb(Ⅱ)ion contaminated water treatment.