Preparation And Adsorption Mechanism Of Bio-adsorbents From Bark

The bark,which is the residue in wood processing process,possess the characteristics of cheap,renewable and environment-friendly.However,the utilization of bark is rare in China,and a lot of bark is abandoned.Therefore,the research on the high-value utilization of bark is of great significance due to the shortage of resources and the increasingly serious environmental pollution.Pinus massoniana is the main species of coniferous plantation in FuJian.So in this paper,the Pinus massoniana bark was dissolved in ionic liquids followed by fractionation using anti-solvents.And then two adsorbents,biochar adsorbent and nanocellulose adsorbent,were prepared from the separated lignin and cellulose,respectively.The adsorption properties of the two adsorbents towards heavy metal ions in the solution were investigated.The Pinus massoniana bark was dissolved in 1-butyl-3-methy limidazolium methylimidazolium chloride?[Bmim]Cl?and1-allyl-3-methyl imidazolium chloride?[Amim]Cl?,and the structure of the bark before and after dissolution were characterized.Three components of Pinus massoniana bark were separated using acetone solution or NaOH solution as anti-solvents.The results showed that the Pinus massoniana bark could be dissolved in two kinds of ionic liquids,the solubility of the bark in the ionic liquids could be improved by increasing the temperature,prolonging the reaction time and ball milling process.The crystal of the regenerated Pinus massoniana bark was disappeared due to the existence of lignin and other components with mechanical stirring,but the FTIR analysis of the bark showed that the chemical structure of each component had not changed after dissolution and regeneration process.The fraction of cellulose,lignin and hemicellulose from Pinus massoniana bark could be realized by using acetone solution or NaOH solution as anti-solvent,and the separation efficiency of the components could be promoted by ball milling.FTIR analysis of each component further confirmed that the main components of the fraction are cellulose,lignin and hemicellulose,respectively.Biochar was prepared from separated lignin with KOH or H₃PO₄ as activating agent,and its adsorption properties for Cu²⁺and Ni²⁺in solution were studied.The results showed that the under the following conditions:soaking time of activating agent was 24h,the concentration of KOH and H₃PO₄ was 10wt%and 40wt%,respectiovely,the carbonation temperature was 600?,and the heating rate was 15?/min,biochar with high yield could be obtained.A large number of pores was observed on the surface of the prepared biochar,and the specific surface area could reach 229 m²/g.The adsorption capacity of the prepared biochar to Cu²⁺and Ni²⁺in the solution could reach 91.60 mg/g and 72.60 mg/g respectively.The static adsorption of Cu²⁺and Ni²⁺by biochar followed with the Langmuir and Freundlich adsorption isotherms.Kinetics studies revealed that the pseudo-first-order kinetic model fitted well with the experimental data.And the sorption process to be feasible,spontaneous,and endothermic.Regeneration of biochar loaded with metal ions could be achieved by treating with 2.0M HCl solution.Nanocellulose?BNC?was prepared by hydrolysis of the separated cellulose by p-toluene sulfonic acid,and then the nanocellulose absorbent?BNCA?was obtained by the graft copolymerization of BCN.The adsorption properties of the BNCA was investigated using Pb²⁺and Cd²⁺as adsorbate.The analysis of the response surface showed that the yield of BNC can reach 75.47%when the reaction temperature was 59.70?,the reaction time was 1.43h and the concentration of p-toluene sulfonic acid is 69.39wt%.COO-functional groups could be observed on the surface of BNCA.Under the optimum conditions,the static adsorption capacity of BNCA for Pb²⁺and Cd²⁺could reach 124.56 and 75.68mg/g,respectivelly.The sorption process was spontaneous,exothermal and followed the Langmuir and Freundlich adsorption isotherms.Kinetics study revealed that pseudo-second-order was closed to the experimental data.Moreover,the BNCA had good regeneration and reuse performance.