The phenol isotherms were fitted with the Radke and Prausnitz three-parameter adsorption isotherm model within Vertical Bar3 5Vertical Bar3< error. Adsorption equilibrium with the Amberlite XAD-8 resin slurry was reached after 44 hr for benzoic acid and after 104 hr for phenol. The adsorption of phenol and benzoic acid from dilute aqueous solution onto macroreticular resin was studied by a radiotracer technique for 0.4948-0.0003 mg/ml benzoic acid solutions at 25/sup 0/C and for similar concentrations of phenol at 0/sup 0/, 25/sup 0/, and 70/sup 0/C. One way of overcoming this problem would be to incorporate the NPBA onto a solid support. Losses of NPBA into the aqueous phase could lead to problems, poor economics in industrial separation processes. The complexation is probably through formation of an acid-base ion pair. It was found that TOMA + can extract lactic acid to an extent comparable to the uptake of lactic acid by NPB. Overloading is also observed in extraction of tactic acid, but through a different mechanism.
The -OH group on the NPB - which is left uncomplexed after one solute molecule had bound to the other two -OH groups may be responsible for the overloading.
Assumption of 1:1 complex is not valid for 1, 2-propanediol, which showed overloading (more than one mole of solute complexed to one mole NPB -) at higher concentrations. the complexation constants increase with increasing number of -OH groups available for complexation. The 1:1 complexation constants for the solutes glycerol, fructose and sorbitol follow trends similar to complexation with B(OH) 4 - (aq.), more » i.e. All solutes complexed with NPB -, with all complexes containing only one NPB - per complex. Partition coefficients, distribution ratios and loadings are reported for varying concentrations of solute and NPB. Batch extraction experiments were performed at 25☌. Solutes investigated were 1,2-propanediol, glycerol, fructose, sorbitol and lactic acid. NPBA and Aliquat 336 (quaternary amine) is dissolved in 2-ethyl-l-hexanol, and the extractant is contacted with aq. The complexing extractant agent investigated in this work is 3-nitrophenylboronic acid (NPBA) in its anionic form (NPB). However, capacity losses occur during acetone regeneration cycles, because acetone is more strongly held on the bed than is methanol.
With methanol as the regenerant, fixed-bed adsorption and regeneration could be operated over several cycles with minimal loss of bed capacity. From batch equilibrium experiments, the affinity and capacity (25 C) of carbons for single and multiple 3 wt.%), lower volumetric flow rate (3-15 bed volumes/h), and uniform particle size or more » particle-size distribution. Several different experimental methods were used to understand better the mechanisms of adsorption of glycerol, glycols, and sugars from dilute aqueous solution onto activated carbons.
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