Preparation Of Carbon-based Functional Material For The Adsorption Of Gallium

Carbon materials are widely used for the adsorption of metal ions due to their unique advantages such as high specific surface area,excellent chemical stability,easy modification and developed pore structure.In this paper,the hydroxyl groups functionalized tremella-like 3D carbon nanosheets,mesoporous carbon materials and layered porous carbon adsorbents were successfully prepared,and the various characteristics of materials were studied.The adsorption performance of gallium were also discussed.The results of research were as follows:Using sodium citrate as the carbon source,the 3D tremella-like carbon nanosheets were prepared by direct carbonization method,and titanium dioxide and sorbitol which were rich in hydroxyl groups were successfully combined with the carbon nanosheet.The prepared composite can improve the hydrophilicity and reproducibility of the carbon material,solve the problem that titanium dioxide was difficult to recycle in aqueous solution as an adsorbent,and increase the number of functional groups on the surface of the adsorbent.It can effectively improve the adsorption performance of the gallium ions.The experimental results showed that the3DCN800-BT10-S0.5 had the best adsorption performance on gallium when the carbonization temperature was 800℃,the amount of butyl titanate and sorbitol added were 10 mL and 0.5 g.The adsorption capacity of gallium could reach 102.39 mg g^-1（pH 3）,which was consistent with the Langmuir isotherm.According to the results of titration of surface functional groups,FTIR and XPS,the adsorption mechanism was deduced as the cation exchange of Ga（OH）₂⁺,Ga（OH）²⁺,or Ga³⁺with H⁺of the3DCN800-BT10-S0.5 form O-Ga bonds.Ga（III）could well separate from coexisting ions containing other similar competitive metal ions such as Ge（IV）,Zn（II）,Al（III）and Cu（II）in pH 3.After six adsorption-dedorption experiments,3DCN800-BT10-S0.5 still had a recover rate more than 90%,indicating that3DCN800-BT10-S0.5 has good cycle performance.In order to shorten the reaction time to improve the efficiency and increase the specific surface area of the carbon material,chitosan which was a kind of natural,non-toxic,mo pullution,low cost and renewable biomass material.The 3D layered porous material with a high specific surface area of 2997.127 m² g^-11 was prepared by combination of hydrothermal carbonization and chemical activation.The adsorbent can not only preserve the rich carbon content,structural diversity and a large number of functional groups on the surface of chitosan,but also solve the problem that chitosan was not applicable as an adsorbent under acidic conditions.The results proved that the adsorption of Ga（III）by CS-800 conformed to the pseudo-second-order kinetic model,which was an endothermic and spontaneous reaction with increase in chaos.After six adsorption-desorption experiments,the recovery rate of gallium for the CS-800 could still reach more than 90%,which showed that CS-800 has good regeneration ability.The pore utilization rate of microporous carbon materials was low,and it would increase the difficulty of desorption.However,the pore size and pore space of mesoporous carbon materials have been expanded,which was conductive to the adsorption and transmission of substances,and increase the chance of contact with gallium ion.Therefore,resorcinol was used as the carbon source,F127 was used as the soft template,and hexamethylene tetramine was used as the slow release source of formaldehyde.The mesoporous carbon material F-C with an aperture of 3.6 nm was successfully prepared.Then,the adsorbent F-C-2 which was obtained after acidification with 2 mol L^-11 sulfuric acid had a maximum saturated adsorption capacity of 132.09 mg g^-11 in gallium solution at pH 3.Not only did F-C-2 have good selectivity for Ga（III）in pH 3,but also can achieve effective separation between Ga（III）and Al（III）when the acidity of the solution was 1 mol L^-1,pH 1 and 3.After six adsorption-desorption experiments,the recovery of gallium from F-C-2 was still above 88%.It showed that F-C-2 had good regeneration ability and water stability.