Preparation Of A Novel Spherical Lignin Adsorbent For Metal Ions And Its Application Research

The black liquor from the pulping process was adopted to prepare the spherical lignin beads, denoted as SLB, by the reversed-phase suspension technique. Then the spherical lignin adsorbent (denoted as SLA) was prepared by the graft copolymerization. And, the adsorption performances of the adsorbent were comprehensively studied by using the metal ions as adsorbates.SLB was prepared by the orthogonal and signal-factor experiments to optimize the preparation conditions. And, the ideal spherical lignin beads with the 85.77% of the yield could be obtained under the such conditions as 1:1.5 of volume ratio of the transformer oil with chlorobenzene, 3:1 of the volume ratio of the oil and water, 1.2% of the neopelex dosage and 0.6% of the gelatin dosage as well as 8% of the epichlorohydrin dosage at the agitation speed of 250 r?min-1at 60℃ for 1 h and subsequently at 90℃ for anther 1 h. The physicochemical characteristics of SLB indicated that SLB showed good hydrophilicity, high acid and alkaline endurance.The SLA was prepared by grafting the acrylic acid onto the back-bone of SLB initiated with the Fenton agent. The optimum preparation conditions were also obtained by the orthogonal and signal-factor experiments. The optimum preparation conditions of the SLA included 40 mmol?L-1 of the initiator concentration, 1.25 mol?L-1 of the monomer concentration of acrylic acid, 40℃ of the reaction temperature and 2 h of the reaction time. The grafting percentage of SLA prepared under the above conditions could reach 30.41%. And, the SLA showed high thermal endurance, high oxidation endurance and bio-degradation endurance as well as the acid and alkaline endurance.The adsorption properties of the SLA were comprehensively studied in two ways of static adsorption and mobile adsorption. And, the effect factors were also optimized. Moreover, the adsorption mechanisms, i.e., the adsorption thermodynamics and kinetics were explored. The adsorption of such metal ions as Cu2+,Ni2+,Zn2+,Pb2+,Cd2+ on the SLA has found to be concentration,pH and tenperature dependent. The SLA showed excellent adsorption capacities for the above metal ions. The adsorption capacities could reach 30.24 mg?g-1, 27.15 mg?g-1, 32.14 mg?g-1, 75.75 mg?g-1 and 45.39 mg?g-1 respectively. The static adsorption processes followed the Langmuir and Freundlich adsorption isotherm equations. It could be concluded from the adsorption thermodynamics and kinetics that the chemical adsorption was predominant in the adsorption process of metal ions on the SLA. The adsorption rate was controlled by two diffusion models of surface diffusion process and intraparticle diffusion process, but the intraparticle diffusion process played a more significant role during the adsorption process. And, the SLA had such advantages as easy regeneration, high recovery and reusability etc.Consequently, SLA will have a prospective application in the adsorpetion and purification field owing to its excellent adsorption properties and its renewable and abundant raw materials.