Preparation And Adsorption Capacity Of Quaternary Ammonium Salt Of Lignin-Sodium Alginate Polyampholyte

Lignin is a three-dimensional, reticular and aromatic polymer in plant cells, which can be used directly as an adsorbent for the sake of its hydroxyl and carboxyl functional groups contained in the molecule. However, how to improve its amorphous structure has become increasingly important to researchers in this field, such as the development of the lignin derivative of the product.In this paper, two kind of quaternary ammonium salt of lignin-sodium alginate polyampholyte (QL-SA) was prepared with quaternary ammonium salt of lignins (QL) and sodium alginate (SA), thus increasing the contents of quaternary ammonium cations, carboxylate ions and molecules. It was researched on the flocculation performance on two different types of dyes, which were acid black ATT and methylene blue, and its adsorption capacity on different metal ions, Cu(Ⅱ) and Cr(Ⅵ), were investigated according to major influencing factors. This was aimed to provide a new and feasibility solution for the alkali lignin in its application as an absorbent and the rational treatment with waste water. The results were as follows:QL were trimethyl quaternary ammonium lignin (T-QL) and dimethyl diallyl quaternary ammonium lignin (D-QL) in this paper, respectively. The structures of QL-SA (T-QL-SA and D-QL-SA) were analyzed by FTIR, SEM amd TG/DTG which indicated that QL and SA were grafted successfully, the regularity and thermal stability of QL-SA was markedly superior to QL and SA, and its appearance and solubility properties had a significant change. It was also suggested that QL-SA had a wider range of applications, especially the impact of pH, for the isoelectric point of T-QL-SA was5.76, ranging from4to10, while that of D-QL-SA was4.22, which compared to T-QL-SA was more sensitive to pH value.The effects of QL-SA on the adsorption capacity of Cu(Ⅱ) and Cr(Ⅵ) were investigated with simulated wastewater. The maximum adsorption capacity of T-QL-SA on Cu(Ⅱ) at pH5and Cr(Ⅵ) at pH4, dosage0.1g/L; while the maximum of D-QL-SA on Cu(Ⅱ) at pH5.5and Cr(Ⅵ) at pH7, dosage0.1g/L. The adsorption process can be described by the pseudo-second-order kinetic model. The adsorption isotherms data of T-QL-SA on Cu(Ⅱ) was fitted well by Freundlich and that of D-QL-SA was Langmuir models. However, both of T-QL-SA and D-QL-SA on Cr(Ⅵ) were described better by Langmuir models and the adsorption capacities of QL-SA on Cr(Ⅵ) were close when the concentration range from30mg/L to90mg/L. The modified lignin, compared with the raw material lignin, had a certain value on the adsorption of metal ions, especially on the adsorption of Cr (Ⅵ).The effects of QL-SA on the adsorption capacity of Acid Black ATT and methylene blue were investigated with simulated dyes, which were showed as follow:the optimum removal rates of QL-SA on acid black ATT were90.08%and86.24%, respectively; those on methylene blue were97.11%and99.15%, both of theirs were superior to raw meterials. Compared with T-QL-SA, D-QL-SA had a lower flocculation performance of Acid black ATT, but a higher of methylene blue. According to the datum, the flocculation mechanism of these two amphoteric flocculants was mainly via electrical neutralization and bridging role, accompanied by sweep netting and volume effect.The advantages of QL-SA lies in its wide range of applications, which can handle different polarities of industrial wastewater, fast absorption rates, clear stratification and ease of recycling. Therefore, the QL-SA exhibits a good practical prospect.