| With the rapid development of social technology, waste water becomes a more and more serious problem. Considerable attention was given to recycle and reuse of waste water due to increasing water demand globally. The adsorption method has many good advantages such as simple operation, good removal effect and adsorbent source widely. In this paper, lotus leaf as a kind of biomass adsorbent materials was used to deal with organic wastewater and dyeing wastewater. Its main ingredients are composed of cellulose, hemicellulose and lignin etc, the molecule contains a large number of hydroxyl and carboxyl groups, using original groups in these molecules, using triethylenetetramine as modifying agent to modify the lotus leaf.The content of amino groups in the modified lotus leaf increased, enhancing the adsorption of anionic dyes and organic matter.The raw lotus leaf was used to this experiment, using triethylenetetramine to modify lotus leaf. The important factors including the reaction temperature, reaction time and solid to liquid(triethylenetetramine and lotus leaf ratio) ratio, which will affect the adsorption of hydroquinone and light green were investigated. The optimum conditions have been identified. Response surface analysis method was applied to optimize the modification conditions of lotus leaf, and the optimization results are verified. The correlation coefficient and variance analysis showed that the response surface analysis experiment scheme design method is reliable. The optimal conditions for adsorption hydroquinone were reaction temperature of 81.8 ℃,reaction time of 228 min and the liquid to solid ratio of 3:1. The modified lotus leaf was made in the optimum condition, the average adsorption capacity of hydroquinone was 0.649 mmol/g. Therefore, the model has strong reliability. And The optimal conditions for adsorption light green as response value were reaction temperature of 87.2 ℃, reaction time of 250 min and solid to liquid ratio of 3:1. The modified lotus leaf in optimal condition was prepared, and the average adsorption amount of light green is 0.144 mmol/g.The adsorption characteristic of hydroquinone and light green using themodified lotus leaf was studied. The experiments were conducted to study the factors affecting the adsorption process, such as the contact time, the dosage of adsorbent, the initial pH, the initial concentration and the system temperature. The results indicated that 360 min and 420 min were seen as the adsorption equilibrium time for adsorption of hydroquinone and light green, respectively. The maximum adsorption capacity of modified lotus leaf for hydroquinone was 1.288 mmol/g at293 K. The maximum adsorption capacity of modified lotus leaf for light green was0.501 mmol/g at 298 K. The adsorption of is favorable at high temperatures for adsorption of hydroquinone and light green. Langmuir, Freundlich, Koble-Corrigan,Temkin and Redlich-Peterson isotherm models were used to farther explore the react mechanism, the non-linear regressive analysis of the equilibrium adsorption data was investigated, respectively. The results indicated that the adsorption of hydroquinone onto the modified lotus leaf follows Langmuir and Temkin isotherm adsorption models well, moreover, the adsorption of onto modified lotus leaf follows Langmuir, Freundlich and Temkin isotherm adsorption models well. The kinetic studies for hydroquinone and light green indicated that adsorption process followed the pseudo second-order kinetic model. The adsorption process was controlled by membrane diffusion and intra-particle diffusionMultiple analytical techniques such as FTIR were employed to examine the micro-structure of the raw lotus leaf, the alkalization and the modified lotus leaf.The results showed that the large number of amine group was added into the lotus leaf. |
PDF Full Text Request