Preparation Of Lignin-based Adsorbent And Study Of Properties

There is a large number of lignin. Lignin is a cheap, environmental friendly and renewable natural resource. Industrial lignin mainly comes from pulp and papermaking industry. However, parts of industrial lignin were directly discharged without any treatment, which could not only waste resources but also pollute the environment. Adsorbents are used in many areas, including material purification and separation, environmental control, water treatment, chromatography, organic synthesis, separation and purification of biological medicine and drugs. Because of a series of active groups contained in lignin molecules, lignin has a certain adsorption. Therefore, it can be made in multifunctional, high performance lignin-based adsorbent through appropriate modification polymerization. This not only solves the problem of environmental pollution, but also it will achieve the purpose of dealing with waste by waste. In this paper, magnesium lignosulfonate was used to prepare lignin-based adsorbent with solidification, activation methods. The static adsorption experiments were applied to measure the adsorption performance of lignin-based adsorbent for methylene blue, and the structure of adsorbent was characterized by thermogravimetric analysis, FTIR and BET methods.The conditions of cross-linking reaction were determined by orthogonal, single factor experiments. The degree of swelling, copper removal rate of polymer, which was prepared under conditions of 100℃of reaction temperature,60% of magnesium lignosulfonate concentration,4mol/L of acidity and 10% of the amount of formaldehyde, were 267.37%,62.72%, respectively. The adsorption capacity of carbonaceous sorbent for methylene blue, iodine and surface area, which was prepared with cross-linked product and phosphoric acid under conditions of 400℃of activation temperature,2 of impregnation ratio and 2 hour of activation time, were 142.5mg/g,946.43mg/g,642.38m2/g, respectively. This is better than the adsorption performance of carbonized resin of lignin being prepared by Zhu Jianhua.The results of thermogravimetric analysis show that magnesium lignosulfonate is a mixture consisted of a series of degradation products. At heating process (form room temperature to 800℃), it was occurring physical or chemical reactions. As a result, the weight was decreasing continuously. The cross-linking reaction could change the thermal behavior of magnesium lignosulfonate. At 360℃, pyrolysis reaction rate of magnesium lignosulfonate could be reduced by phosphoric acid. After cross-linking and activation, infrared spectrum of magnesium lignosulfonate retains the basic structure character of lignin except for the burn off of sulfonic groups.In order to further study the lignin-based carbonaceous adsorbent adsorption on methylene blue cationic dye, the static adsorption experiments was applied. The results show that with increasing activation time, the adsorption value of lignin-based carbonaceous adsorbent on methylene blue increased. At 490min, the adsorption equilibrium was achieved, and the removal rate, remaining concentration, equilibrium adsorption capacity of methylene blue were 85%,305mg/L,677mg/g, respectively. Besides, with concentration of methylene blue being increased, its equilibrium adsorption capacity increased gradually. The equilibrium adsorption capacity reached 407.53mg/L when concentration of methylene blue was 2500mg/L. The adsorption characteristic of lignin-based carbonaceous adsorbent for methylene blue is adapted to Langmuir adsorption isotherm.