The Studies On Adsorption Behaviors Of Low Concentration Organic Acids On Crosslinked Chitosan Resin

In this thesis ,adsorption of organic acids of low concentration as benzoic acid, nitrobenzoic acid, chlorobenzoic acid, m-toluic acid in different medium environment (organic acid + water ,or organic acid + water + salt ,or organic acid + acid + organic solvent ,or organic acid + acid + organic solvent + salt ) on crosslinked chitosan resin(CCTS) as adsorbent was studied.By potentiometric method,we can trace the adsorption process on-line.The apparent adsorption rate constant (k_t) was calculated by the solid-liquid interface dynamics equation.The solid-liquid adsorption behavior of CCTS and organic acids in ternary or quaternary system was studied particularly.With the salt effect theory,the influence of medium (LiCl,NaCl,KCl,LiBr, NaBr,KBr,MgCl₂,CaCl₂,SrCl₂)concentration on adsorption rate was discussed and the regularity of adsorption process was found.Valuable theory parameter would be provided for the industrialized production of the adsorption of organic acids on CCTS and the design of the best conditions for industrial art.The experimental results indicated that:1. The adsorption behavior in solid-liquid system was traced by potentiometeric method ,the relative error is less than 4%,which accords with the experimental requirement of solid-liquid adsorption system .2. The adsorption process of organic acids of low concentration on CCTS obeys monolayer adsorption mechanism.3. The added salt has acceleration effect to the adsorption of organic acids in low concentration on CCTS .The adsorption rate in the added salt system is larger than that without the added salt system .4. The adsorption rate increase with an increase of the concentration of the salt.Namely k_te(盐)=0.006mol/L>k_te(盐)=0.004mol/L>k_te(盐)=0.002mol/L>k_te(盐)=0.001mol/L> k₍t(盐)=0.000mol/L.Theadsorption rate of divalent salt (MgCl2, CaCl2, SrCl2) was larger than that of monovalent salt (LiCl, NaCl, KCl, LiBr, NaBr, KBr).5. A good line relationship is found between the concentration of the salt and the activity coefficient of acid. A good explanation can be given by salt effect theory ; the addition of salt serves for salting-out. The larger the salt concentration is, the stronger the salting-out, the larger the salting-out constant ks, and the larger the activity coefficient are. Thus the quicker the adsorption rate.6. When CCTS adsorbs the ramification of benzoic acid, the substituted group position on nitrobenzoic acids affects the adsorption rate is.7. The increase of methanol or ethanol percentage in solutions led to the increase of adsorption rates of m-toluic acid on CCTS. The apparent adsorption rate constant was increased when the concentration of methanol or ethanol was increased.8. The adsorption center of CCTS is the free surface amino. Under the same condition, the more amino content of CCTS is , the larger apparent adsorption rate constant (k,) and adsorption rates are.