Preparation and application of novel chitosan-cellulose composite materials to adsorb Pb(Ⅱ) and Cr(Ⅵ) ions from water

This paper reported the preparation and application of novel chitosan-cellulose composite absorbents for the adsorption of Pb(Ⅱ) and Cr(VI) ions in water. First, oxycellulose or dialdehyde cellulose (DAC) was prepared by sodium periodate oxidation of microcrystalline cellulose (MCC). Second, based on the mechanism of the Mannich reaction, a chitosan/cellulose-based adsorbent (TSFCD) was produced through a cross-linking reaction of thiosemicarbazide (TS) with DAC and chitosan (CS), which was designed specifically for the adsorption of Cr⁶⁺ ions from water. Similarly, another chitosan/cellulose-based adsorbent (DBFCM) was also prepared with 2,5-dithiobiurea (DB) as the cross-linking agent for the adsorption of Pb²⁺ ions in water. The adsorption performance of TSFCD and DBFCM for Cr⁶⁺ and Pb²⁺ ions, respectively, was investigated under various process conditions. Variables included adsorption temperature, time, initial metal ion concentration, pH, and adsorbent dosage. The adsorption kinetics of TSFCD and DBFCM were studied, and isothermal models were developed. Results showed that the adsorption amount increased with the increase of the reaction time, and reached a maximum at about 300 min for the TSFCD/Cr⁶⁺ system, and at about 240 min for DBFCM/Pb²⁺ system. The adsorption performance of TSFCD for Cr⁶⁺ and DBFCM for Pb²⁺ improved at higher temperature, and leveled off at 40℃ and 50℃, respectively. In addition, the removal rate of Cr⁶⁺ increased from 49.96% to 70.22% when the TSFCD dosage increased from 0.5 g/L to 3.5 g/L. Similarly, the removal rate of Pb²⁺ increased from 22.23% to 99.45% with the increase of DBFCM dosage from 0.5g/L to 5.0g/L. The adsorption processes of Pb²⁺ and Cr⁶⁺ were in line with the pseudo-second-order kinetic and the Langmuir isothermal model.