Preparation And Adsorption Properties Of Alkali Lignin-Based Poly (Catechol-Amine) Adsorbent

Lignin is a kind of high aromatic and low value biomass residue.Due to the rich functional groups and good chemical reactivity of lignin,adsorption materials based on lignin have attracted wide attention in recent years.In this thesis,the use of cost-effective,relatively simple to prepare,good adsorption performance of polyphenolamine materials on lignin modification,preparation of a variety of new lignin-based polyphenolamine adsorption materials,for the removal of Cr（Ⅵ）and dyes in wastewater.The structure,composition and properties were characterised using a variety of methodologies.The effect of each of these elements on the adsorption performance of the adsorbent was systematically examined.The experimental data show that the adsorption behavior conforms to the quasi-second-order kinetic model and Langmuir isothermal model.The removal mechanism of heavy metal ions and dye ions was simulated by this model.In this thesis,it is mainly divided into three jobs:（1）A novel alkali-lignin-based adsorption material,alkali lignin-based poly（tetraethylenepentamine-pyrogallol）（AL-PTAP）,was prepared by mannich reaction and catechol-amine reaction to remove Cr（Ⅵ）.The optimum preparation and adsorption conditions of adsorbent were investigated by changing various conditions in the process of preparation and adsorption.The experimental data show that the adsorption behavior conforms to the quasi-second-order kinetic model and Langmuir isothermal model.The maximum adsorption capacity is 769.2 mg g^-1,which is much higher than that of alkali lignin（AL）.AL-PTAP can achieve a removal rate of almost 100%for Cr（Ⅵ）solutions with a concentration of less than 90 mg L^-1 at 1 min.Furthermore,the toxic Cr（Ⅵ）is partly reduced to nontoxic Cr（Ⅲ）.The XPS results showed that both the amine group and the hydroxyl group in AL-PTAP played important roles in the adsorption process of Cr（Ⅵ）.AL-PTAP removed Cr（Ⅵ）by electrostatic adsorption and chemical reduction.By simulating complex wastewater with several common metal ions and anions,AL-PTAP can maintain high adsorption capacity in these simulated wastewater and has good adsorption stability.（2）This work improved the preparation method in Chapter 2,proposed a two-step mannich reaction to aminate lignin,using four amination methods to prepare alkali lignin-based polyphenol amine adsorbent.The adsorbents prepared by four amination methods have higher adsorption capacity and yield.By comparing the adsorption capacity and yield of the adsorbents prepared by four methods,the best preparation method was selected.The adsorbent（AL-PPLA）prepared by method 2 increased by more than 20%when the molar ratio of phenacinol to tetraethylenepentamine was 1:1,1.5:1,2:1.AL-PPLA has excellent adsorption performance,the adsorption capacity of Cr（Ⅵ）can reach805.8mg/g,the adsorption capacity of Cr（Ⅵ）can reach 486mg/g in 5 minutes,and the removal rate of Cr（Ⅵ）solution with the concentration less than 150 mg/L can reach almost 100%.Compared with AL-PTAP,AL-PPLA greatly improves the adsorption performance and has a higher adsorption capacity when the dosage of phlorogamine is low,which can reduce the input of phlorogamine in the reaction system and reduce resource consumption.Thermodynamic studies have shown that the adsorption process is autogenous and inwardly heated.AL-PPLA synergistically adsorbed Cr（Ⅵ）through chemical and physical effects,and part of toxic Cr（Ⅵ）was reduced to less toxic Cr（Ⅲ）.（3）In this work,alkali-lignin-based polyphenolamine adsorbent（AL-PATA）was prepared by reacting alkali-lignin with phenoglucinol.The two-step amine alkali lignin selected in Chapter 3 was used in the preparation process.The prepared AL-PATA has a generously sized specific surface area and pore volume,and the adsorption capacity of Al-PATA in malachite green solution without pH adjustment can reach 869.5mg/g,and502.2mg/g at 5min.Compared with AL-PPLA prepared using phenoglucinol as raw material in Chapter 3,the preparation of alkali lignin-based polyphenolamine adsorbent using tannic acid as raw material can greatly improve the adsorption performance of MG.The influence of various factors on the adsorption properties of AL-PATA was investigated.Thermodynamic studies show that the adsorption of MG by AL-PATA is spontaneous and endothermic.The adsorption behavior conforms to Langmuir model.AL-PATA,as a new kind of green bio-based adsorption material,can remove MG in high capacity in malachite green solution without pH adjustment.In this thesis,a variety of alkali lignin-based polyphenol amine materials have been prepared,which have rich functional groups and large specific surface area,and have high capacity and adsorption characteristics for Cr（Ⅵ）and dye cations.As a new kind of green bio-based adsorption material with high performance,it has broad application potential and prospect.