Preparing Of Alkali Lignin-based Adsorbent And Adsorption The Cationic And Anion Dyes In Aqueous Solution

Most dyes with complex structure are not apt to be degraded,and cancerigenic.Water contamination by dyes has become a serious environmentalissue along with the development of dyeing.Alkali lignin,the by-production in pulp mill,is no adsorption potential to cationic and anion dyes.But the aromatic hydroxyl in aromatic ring enhances the reactivity of the hydrogen atom at ortho-position of the aromatic hydroxyl.In this work,we plan to prepare an alkali lignin-based adsorbent by introducing functional groups which are apt to bind cationic and anion dyes at the ortho-position of the aromatic hydroxyl in alkali lignin molecule.Based on the detailed literature research,the alkali lignin-based adsorbent was prepared successfully by Mannich reaction,the glutamic acid possessing amino and carboxyl was introducedsuccessfully in alkali lignin molecule.N2 adsorption/desorption indicated that thealkali lignin-based adsorbent ismesoporous materials.The adsorption property of alkali lignin-based adsorbent to cationic dyes(methyl violet and malachite green)and anion dye(eosin B)was studied.Alkali lignin-based adsorbent presentedconsiderable adsorption property to cationic and anion dyes.At pH 2~7,the adsorption capacity for methyl violet and malachite green increased with increasing the value of pH,the adsorption capacity for eosin B decreased with increasing the value of pH.The adsorption capacity of methyl violet,malachite green on the adsorbent is 50.6 mg g-1、43.8 mg g-1at pH 7,initial dye concentration 60 mg L 1,adsorbent dosage 1.0 g L 1,respectively.The adsorption capacity of eosin B on the adsorbent is 45.3mg g-1at pH 2,initial dye concentration 60 mg L 1,adsorbent dosage 1.0 g L 1.The adsorption kinetics for these three dyes on the alkali lignin-based adsorbent follows a pseudo-second-order pathway,the equilibrium adsorption data could be describedwell by the Freundlich isotherm equation,and the adsorption process is endothermic(the negative values of ?G0),spontaneous and random(positive values of ?H0 and ?S0).The batch adsorption experiment in the mixture aqueous solution of malachite green and eosin B was conducted.The result suggested that thealkali lignin-based adsorbent is more likely to adsorb malachite green,and the tendency is more obvious in higher initial dyes concentration.Thealkali lignin-based adsorbent prepared from by-production of pulp is anavailable,low-cost biomass–based adsorbent for adsorbing refractory cationic and anion organic dye in effluent.