Preparation Of Modified Alkali Lignin-clay Composite And Its Removal Properties For Antibiotics And Heavy Metals In Water

In this paper,the application of alkali lignin in adsorption was studied.Phosphorylated alkali lignin（PAL）with regular shape was prepared by modification of alkali lignin,and single component and two component adsorption experiments were conducted on antibiotics and heavy metals.The composite（MKL-PAL）was prepared by loading PAL on modified kaolin,and the single component and two component adsorption experiments on antibiotics and heavy metals were carried out.The application of alkali lignin reduction in the removal of antibiotics and heavy metals was investigated.The composite L/P-nZVI@Mnt was prepared by curing nano-iron and montmorillonite with alkali lignin and polyethylenimine crosslinked polymer to adsorb K₂Cr O₄ and degrade antibiotics.The main contents and results are as follows:（1）Using epichlorohydrin linker,phosphate group was grafted onto alkali lignin to prepare phosphorylated alkali lignin（PAL）with regular shape to adsorb levofloxacin hydrochloride（LH）.Through different characterization methods（FTIR,XRD,SEM）,it was proved that the phosphate group was successfully combined with alkali lignin,and the specific surface area of PAL was 9.53 m2/g,which was 5.5 times that of AL.The effects of initial concentration,solution pH,contact time and temperature on the adsorption were systematically studied under static adsorption conditions.The results showed that the optimal supplemental amount was 0.02 g/50 m L.When the concentration of LH was 80 mg/L,the removal rate reached 100 within 80min.The maximum adsorption capacity of PAL for LH was 389.1 mg/g.In the two-component solution of LH and Pb²⁺,the adsorption capacity of PAL for Pb²⁺increased,while the adsorption capacity for LH decreased.The adsorption mechanism of PAL before and after LH adsorption was analyzed by FTIR and XPS characterization.The results show that PAL adsorption of LH is mainly throu ghπ-πinteraction,electrostatic interaction and hydrogen bond.（2）Kaolin loaded with Fe₃O₄（MKL）was prepared by co-precipitation method,and magnetic composite soil（MKL-PAL）was prepared by MKL loaded with PAL to adsorb LH.Thro gh different characterization methods（FTIR,XRD,SEM）,it was proved that Fe₃O₄ was successfully supported on kaolin and PAL coated on Fe₃O₄.The effects of the optimum preparation conditions,addition amount,initial concentration,contact time and temperature of MKL-PAL on the adsorption of LH were systematically studied under static adsorption conditions.The results showed that the adsorption performance of MKL-PAL was the hi ghest when the addition amount of MKL was 0.5 g,and the optimal addition amount was 0.02 g/50 m L.When the concentration of LH was 80 mg/L,the removal rate reached 99.3%within 40min.The maximum adsorption capacity was 528.6 mg/g.Compared with PAL,the adsorption capacity,thermal stability and pH adaptability of MKL-PALwere improved.In the two-component solution of LH and Pb²⁺,the adsorption capacity of MKL-PAL for Pb²⁺increased,while the adsorption capacity for LH decreased.（3）The prepared nanometer iron（nZVI）was loaded on montmorillonite（Mnt）by liquid phase reduction method,and then the Mnt and nZVI were coated with crosslinked polymer of alkali lignin（Al）and polyethylenimine（PEI）to prepare composite L/P-nZVI@Mnt for reducin g K₂Cr O₄ and degrading levofloxacin（Lev）in water.Through different characterization methods（FTIR,XRD,SEM）,it was proved that the cross-linked polymer coated nZVI and intercalated montmorillonite successfully.The adsorption experiments of K₂Cr O₄showed that K₂Cr O₄ could be adsorbed by L/P-nZVI@Mnt and then reduced to non-toxic Cr³⁺by coated nZVI.The experiment of Lev degradation showed that Lev in water can be effectively de graded by using K₂（SO₄）₂ as oxidant.L/P-nZVI@Mnt has a high reusable performance.