Preparation Of Calcium Activated Humic Acid Resin And Its Adsorption Performance For Pb²⁺ In Acidic Wastewater

The oxygen-containing functional groups rich in coal-derived humic acid（HA）can coordinate and adsorb heavy metal ions such as Pb²⁺in wastewater,which can be used for the efficient removal of typical toxic heavy metals.However,due to the Lewis hard base properties of phenolic hydroxyl groups and carboxyl groups in HA macromolecules,and the borderline acidic properties of Pb²⁺,HA faces a selectivity problem in the adsorption separation of Pb²⁺in multi-metal ion coexisting wastewater systems,which limits the deep separation of Pb²⁺and affects the standard discharge of wastewater.In order to solve this problem,a new type of HA adsorption material was constructed in this study and improved its adsorption capacity and selectivity for heavy metal Pb²⁺through functional group and pore structure regulation.This study provides a theoretical basis for the deep purification of lead-containing industrial wastewater and structural regulation of HA adsorption materials.The HA was extracted from Yunnan Zhaotong lignite by alkali-soluble acid precipitation method.The relatively homogeneous HA component was obtained by ultrafiltration grading,and then the HA was fragmented and small-moleculeized by thermal cracking to obtain the chemical structural information of HA fragments and identify typical structures.On this basis,the linear relationship between the maximum adsorption capacity and the structure-effect of HA was established,and it was clarified that carboxylic acid groups are the main controlling factors affecting the adsorption of Pb²⁺/Cd²⁺;The heteroatoms,substituted functional groups,andπelectrons in the typical structure of HA were determined to be the adsorption active sites,and the affinity of heavy metals satisfied double-substituted aromatic ring>single-substituted branched chain>single-substituted fused ring>single-substituted aromatic ring>benzene ring.The binding energy between typical structures of HA and Pb²⁺/Cu²⁺/Cd²⁺was calculated,and the binding energy size satisfied HA-Pb>HA-Cu>HA-Cd.The charge difference between typical structures of HA and heavy metals satisfied O-Pb>O-Cu>O-Cd.According to these conclusions,Mulliken charge can be used as a microscopic criterion for selective adsorption of Pb²⁺by HA.Based on the cognitive basis of the typical chemical structure of HA,a new high-capacity adsorption resin for HA was prepared.Firstly,phenolic resin carbon spheres with adjustable pore structure were prepared by the method of combining template and calcination.Then,phenolic resin carbon spheres and nano-iron were used as the resin skeleton components.The self-assembly between HA and skeleton components was realized through multiphase co-precipitation.Based on the coordination and hydrogen bonding of phenolic hydroxyl and carboxyl of HA,the preparation method for HA high-capacity adsorption resin based on heterogeneous coprecipitation-pore structure regulation and coordination was established.The results showed that under the strong acid system with an initial p H of 1.0,the introduction of humic acid increased the adsorption capacity of the resin to Pb²⁺by nearly 4 times,indicating that the humic acid component and phenolic carbon spherical pore structure jointly constituted the main adsorption active site of the resin,thereby achieving rapid high-capacity adsorption of heavy metal Pb²⁺in wastewater.The stability and applicability of HA resin（HA@PF）in acidic solution environment were verified.The calcium activation method for selective separation of Pb²⁺by strengthening the HA@PF was proposed.Firstly,the structural changes of HA@PF caused by alkali（earth）metal activation were studied,the best way to activate HA@PF by calcium was screened out,and the bridging effect of Ca²⁺on the structure of HA was verified.On the basis of studying the structure and assembly form of HA-nano-iron-phenolic carbon spheres,the combination characteristics of Ca-HA-Fe ternary system and Ca-PF binary system were explored by SEM-EDS,and the interaction between HA,Fe,and Ca was further studied by quantum calculation,and the related cross-linking model of Ca-HA-Fe ternary system was constructed.The coordination ability of HA with Ca²⁺was theoretically calculated,and the stable configuration between Ca²⁺and model compound was established,which further reveal the existence state of HA and Ca²⁺at the microscopic level.Through the analysis of Ca²⁺activated HA@PF（HA-Ca@PF）structure,the high-density active site construction mechanism of Ca²⁺activated HA@PF was revealed.By calculating the proportion of chelation and ion exchange in different solution p H for heavy metal adsorption by HA-Ca@PF,the role of Ca²⁺in adsorption was further explained from a micro perspective.The adsorption selectivity of Pb²⁺in acidic multi-metal ion coexisting wastewater by Calcium activated HA resin（HA-Ca@PF）was studied.The adsorption kinetics,adsorption isotherms,and coexisting ion effects of HA-Ca@PF on Pb²⁺/Cd²⁺mixed solution were studied under different p H solution environments,and it was found that the separation coefficient increased with the increase of p H.The coexisting anions had no obvious influence on the adsorption capacity,and high concentration of SO₄^2-promoted the selective adsorption of Pb²⁺.The multi-ion coexistence system always maintains high adsorption capacity and selectivity for Pb²⁺.In order to investigate the adsorption capacity and practical application performance of HA-Ca@PF for Pb²⁺,the adsorption experiments of simulated wastewater were carried out under five real water quality parameters,which reached the industrial discharge standards.Among them,the wastewater from the battery industry has reached the national sanitary standard for drinking water,which shows that HA-Ca@PF has shown considerable potential in purifying wastewater contaminated by heavy metal.On the basis of previous studies,three potential influencing factors,Mulliken electronegativity,Ca-ion exchange,and metal ion electronegativity,can be used as criteria for selective adsorption of Pb²⁺by HA-Ca@PF.This thesis contains 72 pictures and 42 forms,and 210 pieces of refrences.