Synthesis Of Amoxidized Lignin,carboxylic Lignin Absorbents And The Adsorption For Pb(?)

This dissertation aimed at the problem about the lignin reuse and utilization,and researched lignin sorbents for heavy metal ions which use pulping alkali lignin as raw material.It will provide a new way for lignin products' application.It synthesized three kinds of alkali lignin adsorbents which named carboxymethyl-crosslinked lignin,oxidation-crosslinked lignin,oxidized ammonia lignin adsorbent respectively.It introduced amidogen,carboxyl functional groups through oxidation,carboxymethylation and oxidative ammonolysis modification.Firstly,the experiment synthesized oxide lignin adsorbent with alkali lignin,hydrogen peroxide and formaldehyde as raw materia.It studied the optimization of process through to the feeding ratio,reaction temperature and time.The oxidation sample had 0.65 mmol/L carboxyl content,165.71 mg/g adsorption capacity of Pb²⁺,and the weight average molecular weight was 7900 Da.The carboxymethylated sample had 1.12 mmol/L carboxyl content,171.85 mg/g adsorption capacity of Pb²⁺,and the weight average molecular weight was 9000 Da.The IR and XPS spectra of the sample complex showed that the hydroxyl and carboxyl groups in the sample can be complexed with Pb²⁺,and these were ion exchange,chelation and other chemical reactions.Adsorption pH value,time and metal ion concentration on the adsorption effect were relatively significant,while the adsorption temperature on the adsorption effect was weak.When the pH value was higher than or equal to 5.5,the saturation adsorption capacity were 280.02 mg/g?oxidation-crosslinked lignin?and 300.11 mg/g?carboxymethyl-crosslinked lignin?.Their adsorption process for Pb²⁺ was more consistent with the second-order kinetics equation and Langmuir model,indicating that their adsorption process wasn't only controlled by diffusion,but also by the chemical reaction of complexation.After 3 times of regeneration,the adsorption capacity of carboxymethylated sample was almost constant,the removal rate of oxidized sample was more than 75%.In a word,these adsorbents can be recycled.At last,the experiment synthesized oxidative ammonolysis lignin adsorbent with alkali lignin,hydrogen peroxide and ammonium hydroxide as raw materia.The relationship between the ammonia oxidation reaction conditions and the nitrogen content of the samples was studied.The results showed that the content of nitrogen in the samples decreased with the increasing of the amount of hydrogen peroxide,the amount of mmonium hydroxide,the reaction temperature and the reaction time.The infrared spectrum of the sample shows that the reaction destroyed part of the benzene ring,and reacted with ammonia,brought in amine and amide.The samples adsorbed Pb²⁺ by hydroxyl,amine and amide groups.Relative molecular mass and specific surface area of samples showed that the reaction will be slightly degraded lignin and increase its specific surface area.The saturation adsorption capacity of Pb²⁺ was 130.01 mg/g.The adsorption process of Pb²⁺ was more consistent with the Langmuir model,which showed that it belonged to the adsorption of monolayer.