4-Vinylpyridine-modified post-cross-linked resins and their adsorption of phenol and Rhodamine B

A novel surface imprinted resin for the selective removal of metal-complexed dyes from aqueous solution in batch experiments: ACB GGN as a representative contaminant

Metal-complexed dyes are harmful to the environment and human health because they contain heavy metals and complex organic ligands. It is difficult to separate and recover these dyes from wastewater owing to their complex components and poor selectivity of common adsorbents. In this study, a novel surface molecularly imprinted polymer (SMIP) was prepared using 4-vinyl pyridine as the functional monomer and polystyrene resin as the carrier. SMIP showed better adsorption performance than non-imprinted polymer (SNIP) in the whole pH range with the best adsorption capacity at pH 1.5. The correlation coefficients (R²) fitted by Langmuir and Temkin models were greater than 0.97, and the adsorption was a spontaneous exothermic process. The pseudo-second-order and Elovich models fitted the adsorption kinetic curves well. The adsorption capacity of SMIP was approximately 20% higher than that of SNIP in the salt concentration ranging from 2 to 80 mg/L. In selective adsorption experiments, the relative selectivity coefficients (I) of SMIP for competitors were all greater than 2.41, and the Cr (Ⅲ) components of ACB GGN played a more important role in the recognition performance of SMIP than the sulfonic groups. Adsorption mechanism tests revealed that although the adsorption of ACB GGN by SMIP mainly relied on electrostatic attraction, hydrophobic interactions, π-π conjugation, and Cr (Ⅲ) coordination were also involved. These results show that SMIP has excellent selective adsorption properties for ACB GGN and a promising application potential in the treatment of metal-complexed dye wastewater.

Polymer brush-grafted cotton fiber for the efficient removal of aromatic halogenated disinfection by-products in drinking water

Apart from the activated carbon, other functional adsorbents are usually not frequently reported for the removal of disinfection by-products (DBPs) in drinking water. In this study, a novel polymer brush-grafted cotton fiber was prepared and for the first time used as adsorbents for the efficient removal of aromatic halogenated DBPs in drinking water in the column adsorption mode. Poly (glycidyl methacrylate) (PGMA) was grafted onto the surface of cotton fibers via UV irradiation, and then diethylenetriamine was immobilized on the PGMA polymer brush through amination reaction to obtain the aminated cotton fibers (ACFs). The adsorption performance of the prepared ACF was investigated with eight aromatic halogenated DBPs via dynamic adsorption experiments. The results revealed that ACF showed significantly longer breakthrough point (38,500-225,500 BV) for aromatic halogenated DBPs compared with the granular activated carbon (150-500 BV). Thomas model was used to fit the breakthrough curves, and the theoretical value of the maximum adsorption capacity ranged from 14.76 to 89.47 mg/g. The enhanced adsorption performance of the ACF for aromatic halogenated DBPs was mainly due to the formation of hydrogen bonds. Additionally, the partially protonated amine groups also improved the adsorption performance. Furthermore, the ACF also showed remarkable stability and reusability.

Polar modified dendritic post-cross-linked polymer for Cu2+ adsorption

The polar modified dendritic post-cross-linked polymer, namely HCPD was synthesized and used for adsorptive removal of Cu²⁺ from aqueous solution. The results showed that 5.12 mmol/g of amino and 2.25 mmol/g of carbonyl groups were uploaded on the polymer and these groups were significantly beneficial for Cu²⁺ removal. The maximum capacity reached 157.8 mg/g at 313 K and increased as the temperature increased. The Langmuir model characterized the equilibrium data well and a chemical interaction was involved with the enthalpy change of 49.50 kJ/mol. The pseudo-second-order kinetic model described the kinetic data well and the intra-particle diffusion model was appropriate for characterizing the kinetic adsorption. HCPD could be easily regenerated and the regenerated polymers were effectively recycled for five times without significant loss of the equilibrium capacity. Moreover, Fourier-transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) results revealed that the chelating coordination of the amino and carbonyl groups with Cu²⁺ was the main driving force for the adsorption.

Removal of wastewater phenolic compounds with triethylenetetramine functionalized polystyrene resin

A polyamine functionalized polystyrene resin (PSATA) was prepared via condensation reaction of acetylated polystyrene resin with triethylenetetramine, which, upon NaBH₄ reduction, produced PSATAR. In comparison with the PSATA, the PSATAR with more flexible amine groups shows improved structural properties, and the equilibrium adsorption capacities of phenol, 2-nitrophenol (ONP) and 2,4-dinitrophenol (DNP) in wastewater were up to 1.073, 1.832 and 1.901 mmol/g, respectively. Their adsorption isotherms fit well with the Freundlich model, indicating a multilayer, heterogeneous adsorption nature. Kinetic studies indicated that the adsorption of phenolic compounds conforms to the pseudo-second-order kinetics with the adsorption rate controlled by film diffusion for ONP and DNP, and intra-particle diffusion in the later stage for phenol.

Rhodamine B removal from aqueous solution by CT269DR resin: Static and dynamic study

The adsorption of Rhodamine B onto CT269DR resin has been studied through static and dynamic experiments. The effects of shaking speed, resin dosage, and pH on adsorption were investigated by static experiments. The external mass transfer rate remains substantially unchanged when the shaking speed exceeds 160 r min−1. The optimal pH range is 5–8, and an increase of resin dosage can directly improve the percentage of removal of Rhodamine B. The equilibrium isotherm data of Rhodamine B on CT269DR resin fit the Langmuir adsorption isotherm well. The thermodynamics parameters, Δ H = 69.93 kJ mol−1, Δ S = 326.73 J mol−1 K−1, and Δ G < 0, demonstrate that the adsorption of Rhodamine B onto CT269DR resin is spontaneous and endothermic. The pseudo first-order kinetic model can be successfully used to represent the adsorption process and the activation energy is 25.7 kJ mol−1. The dynamic experiments show that the breakthrough point is advanced when the flow rate increases and the bed adsorption capacity increases with increasing temperature. Furthermore, the desorption using the solution of 2% NaOH is suitable for desorption and reusing process, and scanning electron microscope (SEM) and fourier transform infrared spectroscopy (FT-IR) analysis reveals that used resin has good wear resistance and chemical stability. The results confirm that CT269DR resin can be employed as an efficient adsorbent for the removal of Rhodamine B from wastewater.