Modification Of Activated Carbon Fiber And Its Effect On The Adsorption Of Lead Ions

Activated carbon fiber (ACF) has the special pore structure and surface chemistry properties, having the ability of adsorbing the heavy metal lead ion. For further improving its adsorption capacity, ACF was modified by oxidation, introducing pendant sulfonic acid group and alkalization, and the Pb²⁺ adsorption properties of ACF before and after modification was studied.ACF, oxidized by concentrated nitric acid and hydrogen peroxide, was analyzed by Boehm titration, FT-IR and TG The results of Boehm titration showed the acidic group amount of oxidized ACF increased obviously. It is also proved by FT-IR and TG Compared with raw ACF, acidic groupand carboxyl group content of ACF ,which was oxidized by H₂O₂ at 60℃ for 2 hours, increased 129% and 94%, respectively. XRD analysis indicated that oxidization had no obvious influence the microcrystallite structure ofACF.The oxidized ACF was modified by hydroxy-methylation and then introducing sulfonic acid containing function group. Boehm titration indicanted that acid group increased obviously. It is also proved by FT-IR and TG Approximately 0.8-1.0mmol -SO3H was introduced onto program ACF.Under the varies experiment conditions, the properties of adsorbing Pb²⁺ of ACF, oxidized ACF, ACF with pendant sulfonic acid group and Na-type ACF were completely investigtaed. The results showed all samples had a rapid adsorbtion rates (the equilibration time of adsorption was only 5-10min). The saturation adsorption capacity increased notably with modification. The saturation adsorption capacity of raw ACF was 32.5mgPb²⁺/gACF, while those of oxidized ACF, ACF with pendant sulfonic acid group and Na-type ACF reached 75,106, and 228 mg/g, respectively. The adsorption isotherms of ACF, oxidized ACF and ACF with pendant sulfonic acid group had good agreements with Langmuir isotherm and Freundlich isotherm model, and Na-type ACF had a good agreement with Langmuir isotherm model. The pH value had the great influenced the Pb²⁺ adsorption properties of ACF, whereas oxidized ACF, ACF with pendant sulfonic acid group and Na-type ACF had good adsorption properties in a quite wide range of pH values. Especially, the Pb²⁺ removal efficiency of ACF with pendant sulfonic acid group was 100% at an initial concentration of 40mg Pb²⁺/L and the pH value of 3, contrast to the but the Pb²⁺ removal efficiency of 27% for ACF. The effect of temperature on...