Adsorption Properties Of Co(?) On Carboxymethyl Chitosan Adsorbents

Cobalt wastewater pollution is one of the most urgent environmental problems.In order to removal of Co(?)from wastewater,the method of adsorption is adopted due to its properties of simple and feasible.Three kinds of adsorbents were prepared from carboxymethyl chitosan,and the adsorption properties of these three sorbents for cobalt ions and their adsorption mechanism for cobalt ions were studied.In this work,porous carboxymethyl chitosan beads(PCMC beads)are synthesized by a method of ionic coacervation/chemical crosslinking for removal of Co(?)from aqueous solution,in which using polyethylene glycol(PEG)as a porogen and calcium chloride and glutaraldehyde as a physical and chemical cross-linker,respectively.The structure of the prepared PCMC beads was characterized and analyzed through TGA,BET,SEM,and EDS.The adsorption mechanism of PCMC beads was investigated via FTIR and XPS.It is found that the adsorption equilibrium is reached within 6 h.And the kinetics and equilibrium data are well described by pseudo-second-order kinetics and Langmuir isotherm models.Finally,the adsorption mechanism,including chemical and physical adsorption,is proposed and chemical adsorption is the main adsorption mechanism during the process of removal of Co(?).In addition,the crosslinked carboxymethyl chitosan hydrogel and resin are prepared via cross-linking of glutaraldehyde.And the adsorption behaviour and mechanism of the hydrogel and resin are studied for removal Co(?)from wastewater.The results revealed that the initial pH value of the solution to a large extent affects the adsorption capacity of adsorbents on cobalt ions.The analysis of experimental results indicated that chemical adsorption is the main adsorption method in their adsorption mechanisms.However,the Co(?)adsorption process onto the hydrogel is accompanied by physical adsorption.According to the results of the adsorption properties of three kinds of adsorbents on cobalt ion,the adsorption rate of PCMC beads is the fastest and the adsorption capacity of hydrogel is the largest.But relative to hydrogel,the mechanical properties of the resin can be more adaptable to the complex environment of external adsorption.The adsorption mechanism are all mainly chemical adsorption,accompanied by physical adsorption.