A Study On Aminated And Metal-modified Lignin For The Removal Of Heavy Metal From Water

Adsorption technology is considered as one of the most promising technologies in water treatment because of its low cost,simple operation and high removal rate.Among the reported adsorbents,lignin and its derivatives have attracted the attention of researchers due to their advantages of renewable,biodegradable,cheap and easy to extract.The annual output of lignin in the world can reach 5*10¹⁴ t.A lot of lignin can be extracted from black liquor of papermaking waste liquor by adding some Acidifiers.However,the reactivity of lignin is low,so there are few active sites.Its zeta???potential is negative,so it can not absorb oxygen-containing anions through electrostatic action.Therefore,people use various methods to modify lignin to make lignin have adsorption capacity.Among them,the electronegativity of lignin can be changed by amination modification,so that it has a certain degree of adsorption on oxygen-containing anions in water.At present,there are many studies on the preparation of various aminated modified lignin and its adsorption of oxygen-containing anions in water,but most of the products have weak adsorption capacity,and they do not have the selective adsorption of specific ions,and their reusability is low,which restricts the application of lignin in the field of water treatment.In this paper,metal doped aminated lignin as the research object,the adsorption law,adsorption efficiency,adsorption process,adsorption type and adsorption mechanism of three oxygen-containing anions?Cr?VI?,As?V?,P?V??were studied and analyzed.Based on this,the optimal adsorption system and selective adsorption sequence are proposed,and the practical application of the system in Taiyuan basin is explored,which provides theoretical guidance for the treatment of water environment in real life and industrial application.The main research contents include the following aspects:First of all,aminated lignin adsorbent?a-CL?was prepared by Mannich reaction.The structure and morphology of a-CL were characterized by XRD,SEM,FTIR and XPS.The adsorption capacity,selectivity and separation factors of a-CL for three kinds of oxygen-containing anions?As?V?,P?V?and Cr?VI??were studied.The adsorption isotherm model and adsorption kinetics model of a-CL for As?V?were obtained by fitting.In addition,according to the adsorption mechanism of aminated lignin and different oxygen-containing anions in this paper,the order of binding energy of the three systems is P?V?<Cr?VI?<As?V?.Secondly,on the basis of obtaining aminated lignin adsorbent,we continue to dope it with metal ions.In order to comprehensively compare the influence of different metal ions on lignin doping,we prepared Fe-based lignin respectively?Fe@a-CL?,Cu-based lignin?Cu@a-CL?,Mg-based lignin?Mg@a-CL?and Ca-based lignin?Ca@a-CL?four metal-based aminated lignin?M@a-CL??Fourier transform infrared spectroscopy?FT-IR?,X-ray photoelectron spectroscopy?XPS?,X-ray diffraction?XRD?and scanning electron microscopy?SEM?were used to study four kinds of compounds M@a-CL The adsorbent was characterized and studied M@a-CL.The adsorption properties and selective adsorption of three kinds of oxygen-containing anions were studied in detail,especially As?V?.The corresponding adsorption isotherm model and adsorption were obtained by fitting dynamic model.At the same time M@a-CL The performance of reuse is studied and the reuse rate is obtained.Finally,with Fe@a-CL for example,metal-based aminated lignin was applied to the de-enrichment of groundwater in Taiyuan basin.The adsorption effect of As?V?,Cr?VI?and P?V?in the groundwater of Taiyuan basin is studied.It is shown that,in a certain range,appropriate amount of As?V?,Cr?VI?and P?V?is put into the groundwater samples of Taiyuan basin Fe@a-CL.It can effectively remove three kinds of oxygen-containing anion After full adsorption,the residual concentrations of the three pollutants can meet the requirements of drinking water standard?GB5749-2006?.