The Study On Preparation And Adsorption Performances Of Molasses-based Carbons

Recently, heavy metal pollution, which has toxic and wide affection, has caused some tragedies. Adsorption was often used as an effective method to remove heavy metal ions in the industrial production process. However, the study on the preparation of high efficiency adsorption materials became more and more important. Among the adsorbents, porous carbon had an excellent adsorption effect. But the use of non-renewable energy sources led to the high cost and complicated process of production. In this paper, beet molasses, which were sustainable alternative resources, were explored as raw materials to research the properties and characterizations of porous carbons, especially on sorption.1. Carbons were prepared in the presence of H₃PO₄ at different conditions by carbonization of beet molasses. All the porous carbons obtained had much more mesoporous than microporous. Characterized by SEM, XRD, N2 adsorption, electrochemical station and so on, the structures and performances of porous carbons were analyzed. Porous carbon had a specific surface area of 970 m2 g-1 and exhibited large specific capacitance of 142.2 F g-1. Moreover, the volume of mesoporous occupied total volumes with 87.2 %.2. Porous carbons prepared by molasses were utilized for the removal of Cu（II） and Cd（II） from aqueous solution in batched sorption experiences. The effects of initial concentration of adsorbates, contact time, p H value, temperature and the mass of adsorbents on adsorption of Cu（II） and Cd（II） were explored. Compared with the commercial activated carbon, the adsorption properties of porous carbons were investigated. Via the data of experience, adsorption kinetics and isotherm models were analyzed to speculate the adsorptive process. Results showed that Cu（II） adsorption was better than Cd（II） adsorption and the initial concentration of adsorbates and p H had great influences on the process. In addition, both Cu（II） and Cd（II） adsorptions followed the second order kinetics model and Langmuir model. It was inferred that the adsorptions of Cu（II） and Cd（II） by porous carbons were monolayer adsorption and the processes were chemical adsorption.3. Beet molasses were transformed into hydrochar by hydrothermal carbonization. Two porous carbons employing hydrochar were prepared by using two different activating agents, KOH and H₃PO₄（HKC and HPC）. Then porous carbons were utilized for the removal of Cu（II） and Cd（II） from aqueous solution to study the adsorption properties of porous carbons prepared by different methods. The results indicated that HKC had larger adsorption capacity and solution p H value made an effect on the process. Moreover, both Cu（II） and Cd（II） adsorptions fitted the second order kinetics model and Langmuir model which showed that the adsorptions of Cu（II） and Cd（II） by porous carbons were monolayer adsorption and the processes were deduced to be chemical adsorption. Compared with porous carbons activated by H₃PO₄ directly, it could be discovered that the adsorption processes mainly happened in the mesopore.In a word, the preparation from raw material of liquid phase to porous carbons of solid phase came true by the study on molasses in this paper and the batched sorption experience has provided information for the reuse of molasses.