2-Propanol is used in the industrial crystallization of N-acetyl-D-neuraminic acid (NANA) to reduce its solubility, thereby enhancing its recovery. This study investigates the solubility and transition of NANA in mixed water–2-propanol systems. The solubility of NANA was measured within the temperature range of 273–336 K using high-performance liquid chromatography (HPLC) to determine the equilibrium compositions of NANA in aqueous solutions containing 67.9, 57.2, 35.5, 19.0, 9.2, 2.6 and 0 mol% of 2-propanol. Powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) were employed to investigate the crystalline states of NANA. Thermodynamic properties, such as the entropy and enthalpy of dissolution, were estimated by applying the Van’t Hoff equation to plotting the solubility data. The mechanism of transformation from the anhydrous to dihydrated form is interpreted by considering the change in the water activity (primarily determined by the percentage of water and 2-propanol) of the solution. The results demonstrate that the states of NANA dihydrate and anhydrous NANA in water–2-propanol mixtures depend on both the water activity and temperature. These conclusions can provide useful information for determining the crystallization parameters needed to obtain a desired anhydrous or hydrated phase.

The main aim of this study is to treat palm oil mill effluent (POME) containing phenol, which is a hazardous compound, using activated carbon (AC) prepared from palm kernel shell (PKS), one of the byproducts of the palm oil industry. First, PKS from Thailand was characterized by proximate, elemental, and thermogravimetric analyses. The high carbon and low ash contents in the PKS indicated that PKS is a promising precursor for producing AC. Then, palm kernel shell activated carbon (PKSAC) was prepared using chemical activation with orthophosphoric acid as an activating reagent under various conditions. The physical and chemical properties of the PKSACs were characterized using nitrogen adsorption–desorption and Fourier-transform infrared spectroscopy (FT-IR), respectively. Chemical activation improved the yield and physical properties, even as it changed the chemical properties of PKSACs. The PKSACs thus prepared contained large volumes of micropores. Using the prepared PKSACs, batch equilibrium adsorption was conducted to remove phenol from the POME model. The PKSACs could successfully adsorb and remove phenol from the POME model. The phenol adsorption followed the Langmuir model, and the saturated adsorbed amount of phenol increased with increase in surface area. Based on these results, it is concluded that the treatment of POME using PKSACs produced by chemical activation would be a practicable treatment method since the prepared PKSACs provide a high yield and are capable of treating model hazardous compound in POME.

Improving the performance of capture chromatography is important for the purification of protein drugs such as monoclonal antibodies. Dynamic binding capacities (DBCs) of antibody (IgG) measured for various Protein A chromatography columns were described well with dimensionless plots of E* vs. F*, where E*=DBC/SBC and F*=d_p²/[D_s(Z/u)]. SBC is the static binding capacity, d_p is the particle diameter, D_s is the stationary phase (pore) diffusion coefficient determined by the pulse response experiment at non-binding conditions, Z is the column bed length, and u is the mobile phase velocity. With the E* vs. F* correlation, the repeated cyclic operation optimization method was developed. The total working time (t_tot), the total volume and the concentration of the feed were assumed to be fixed. Then, the number of runs n_c within t_tot was calculated to determine the chromatography column bed volume. It was found that multiple runs can reduce the bed volume significantly, which results in higher productivities.

A previously proposed method for estimating antisolvent crystallization kinetics has been successfully applied to cooling crystallization to yield kinetic parameters for simulating the crystallization process. In particular, the primary nucleation kinetics were analyzed using the modified induction time data, essentially as proposed by Kubota. The number density at the detection point, (N/M)_det, is an important value in the kinetic analysis but is difficult to estimate experimentally. Therefore, the numerical optimization was used to estimate the value of (N/M)_det in the same manner as for antisolvent crystallization. Primary nucleation was detected for both antisolvent and cooling crystallization with a sensitive detection method, visual detection, to reduce the effects of secondary nucleation. As a result, the (N/M)_det values for each method are small and almost identical (approximately 200 #/kg-solvent). The secondary nucleation and growth rate parameters for cooling crystallization were also successfully determined by numerical optimization. All the kinetic parameters determined for cooling crystallization were evaluated with experimental data. Consequently, it is confirmed that these rate parameters can simulate trends in concentration as well as the final number mean diameter of the product crystals with acceptable accuracy. Moreover, the crystallization rate parameters determined for both antisolvent and cooling crystallization were validated with simulations and experimental data from combined crystallization, where antisolvent crystallization is followed by cooling crystallization. The simulation and experimental results for the concentration trend and number mean diameter of the produced crystal were in good agreement. The applicability of our estimation method to both antisolvent and cooling crystallization indicates the broad utility of this method for various crystallization process in the pharmaceutical industry.

We examined the effect of the amino acid asparagine (Asn) as a tailor-made additive to control the face-selective crystal growth rate of L-aspartic acid (L-Asp). The growth rate in the c-axis direction decreased in the presence of L-Asn and D-Asn. The Kubota–Mullin growth model was found to describe the decreased crystal growth in the c-axis direction well. Different factors were found to be responsible for the effectiveness of L-Asn and D-Asn. The different growth–decreasing effects of L-Asn and D-Asn on the L-Asp crystal in the c-axis direction were due to their rates of adsorption on the active sites, which were related to the different configurations of the two additives. Based on AFM observations, a pinning mechanism was proposed as the origin of the decreased growth rate in the presence of L-Asn. We attributed this pinning mechanism to the repulsion between the lone pair of the nitrogen atom of the L-Asn NH₂ group, which was present on the crystal surface due to the adsorption of L-Asn, and the oxygen atom of the L-Asp carboxyl group.

Novel diblock copolymers, based on sulfonated hydrophilic-hydrophobic blocks, were synthesized and investigated for their application as proton exchange membranes. A series of sulfonated poly (¹H,¹H-Penta fluoro n-propyl acrylate)-b-poly(benzenesulfonic acid) copolymers (P(PFPA)-b-P(BSFA)) with various fluorinated block lengths were synthesized via the reversible addition–fragmentation chain-transfer (RAFT) process, and the ethyl group on the sulfonic structure underwent hydrolysis in hot water. The copolymers came to tough membranes through solvent casting, the performance and structural property relationships of these materials were studied, the sequence of diblock copolymers was supported by NMR tests, and GPC demonstrated the low PDI values. Proton conductivity measurements revealed that the proton conductivity improved with the increasing ratio of hydrophilic and hydrophobic block lengths, and the proton exchange membranes (PEMs) are beneficial in trans-plane conductivities. The copolymers exhibited higher strain–stress values along with the ability of greater water uptakes than Nafion. They also depicted better proton conductivities in liquid water as well as under partially hydrated conditions at 80°C. The new materials are good candidates for use in PEM systems.

To achieve the rapid decomposition of refractory organic compounds for water purification, an effective technique for the generation of bromine oxyacids by O₃ fine bubble injection and bromide addition was developed. When O₃ bubbles are micronized in the liquid phase, the absorption of O₃ is accelerated, and OH· generation is promoted because of the increased contact probability between the dissolved O₃ and accumulated OH⁻ at the minute gas–liquid interface. Additionally, when O₃ fine bubbles are supplied into a liquid phase containing Br⁻, further improvement in the oxidation potential of the liquid phase can be expected because of the increased HOBr/BrO⁻ generation with OH· generation. At 298 K, O₃ bubbles with an average diameter (d_bbl) of 50 or 2000 µm were supplied into NaBr aqueous solutions with different initial NaBr concentrations ((C_NaBr)₀). The rate of generation of total oxygen species and the constant value of concentration of total oxygen species (C*_OS) increased with the acceleration of the bromine oxyacid generation, induced by the decrease in d_bbl and the increase in (C_NaBr)₀. Furthermore, the decomposition of tert-butyl alcohol (TBA) by O₃ fine bubble injection at various (C_NaBr)₀ values was carried out. Consequently, the rate constant of TBA decomposition showed a maximum value at C*_OS of 0.54 mmol/L because of the conversion of HOBr/BrO⁻ with a high oxidation potential to BrO₃⁻ with a low oxidation potential, caused by the excess oxidation of Br⁻. Hence, the generation of HOBr/BrO⁻ with O₃ fine bubble injection and bromide addition is effective for achieving enhanced decomposition of refractory organic compounds.