Adsorption Mechanism of Aromatic Sulfonates onto Resins with Different Matrices

Enhanced removal of ammonium from water using sulfonated reed waste biochar-A lab-scale investigation

The removal of excessive ammonium from water is vital for preventing eutrophication of surface water and ensuring drinking water safety. Several studies have explored the use of biochar for removing ammonium from water. However, the efficacy of pristine biochar is generally weak, and various biochar modification approaches have been proposed to enhance adsorption capacity. In this study, biochar obtained from giant reed stalks (300, 500, 700 °C) was modified by sulfonation, and the ammonium adsorption capabilities of both giant reed biochars (RBCs) and sulfonated reed biochars (SRBCs) were assessed. The ammonium adsorption rates of SRBCs were much faster than RBCs, with equilibrium times of ∼2 h and ∼8 h for SRBCs and RBCs, respectively. The Langmuir maximum adsorption capacities of SRBCs were 4.20-5.19 mg N/g for SRBCs, significantly greater than RBCs (1.09-1.92 mg N/g). Physical-chemical characterization methods confirmed the increased levels of carboxylic and sulfonic groups on sulfonated biochar. The reaction of ammonium with these O-containing functional groups was the primary mechanism for the enhancement of ammonium adsorption by SRBCs. To conclude, sulfonation significantly improved the adsorption performance of biochar, suggesting its potential application for ammonium mitigation in water.

Lactic acid separation and recovery from fermentation broth by ion-exchange resin: A review

Lactic acid has become one of the most important chemical substances used in various sectors. Its global market demand has significantly increased in recent years, with a CAGR of 18.7% from 2019 to 2025. Fermentation has been considered the preferred method for producing high-purity lactic acid in the industry over chemical synthesis. However, the recovery and separation of lactic acid from microbial fermentation media are relatively complicated and expensive, especially in the process relating to second-generation (2G) lactic acid recovery. This article reviews the development and progress related to lactic acid separation and recovery from fermentation broth. Various aspects are discussed thoroughly, such as the mechanism of lactic acid production through fermentation, the crucial factors that influence the fermentation process, and the separation and recovery process of conventional and advanced lactic acid separation methods. This review's highlight is the recovery of lactic acid by adsorption technique using ion-exchange resins with a brief focus on the potential of in-site separation strategies alongside the important factors that influenced the lactic acid recovery process by ion exchange. Apart from that, other lactic acid separation techniques, such as chemical neutralization, liquid-liquid extraction, membrane separation, and distillation, are also thoroughly reviewed.

Effect of Functional Group Density of Anion Exchange Resins on Removal of p-Toluene Sulfonic Acid from Aqueous Solution

Adsorption using anion exchange resins is an efficient method for the removal of aromatic sulfonic acids (ASAs) from industrial wastewater. In this study, a series of weak-base anion exchangers (SD1–SD5) were synthesized to investigate the effect of functional group density of resins on the adsorption of ASAs from wastewater containing competitive inorganic anions. p-Toluene sulfonic acid (PTSA) was selected as a target pollutant, and Na2SO4 was chosen as the competitive inorganic salt because of its widespread existence in industrial wastewater. Adsorption performances of these resins were evaluated and compared in terms of selectivity, kinetics, isotherms, regeneration, and dynamic adsorption behavior. Importantly, the PTSA uptake increased with the raising content of functional groups on resins in the absence of Na2SO4; however, in the presence of a high level of Na2SO4 (for example, ≥1%), a decrease in the functional group density could improve the adsorption capacity of resins for PTSA. Moreover, desorption and fixed bed column experiments were conducted in all resins, thereby confirming the effect of functional group density of resins on the PTSA adsorption in actual application. In brief, this research will provide a better understanding for the design and preparation of anion exchangers for the effective removal of ASA from wastewater.

Adsorption behavior of benzenesulfonic acid by novel weakly basic anion exchange resins

Two novel weakly basic anion exchange resins (SZ-1 and SZ-2) were prepared via the reaction of macroporous chloromethylated polystyrene-divinylbenzene (Cl-PS-DVB) beads with dicyclohexylamine and piperidine, respectively. The physicochemical structures of the resulting resins were characterized using Fourier Transform Infrared Spectroscopy and pore size distribution analysis. The adsorption behavior of SZ-1 and SZ-2 for benzenesulfonic acid (BA) was evaluated, and the common commercial weakly basic anion exchanger D301 was also employed for comparison purpose. Adsorption isotherms and influence of solution pH, temperature and coexisting competitive inorganic salts (Na₂SO₄ and NaCl) on adsorption behavior were investigated and the optimum desorption agent was obtained. Adsorption isotherms of BA were found to be well represented by the Langmuir model. Thermodynamic parameters involving ΔH, ΔG and ΔS were also calculated and the results indicate that adsorption is an exothermic and spontaneous process. Enhanced selectivity of BA sorption over sulfate on the two novel resins was observed by comparison with the commercial anion exchanger D301. The fact that the tested resins loaded with BA can be efficiently regenerated by NaCl solution indicates the reversible sorption process. From a mechanistic viewpoint, this observation clearly suggests that electrostatic interaction is the predominant adsorption mechanism. Furthermore, results of column tests show that SZ-1 possesses a better adsorption property than D301, which reinforces the feasibility of SZ-1 for potential industrial application.

Fast track for quantitative isolation of lignosulfonates from spent sulfite liquors

In this study, a novel approach for isolation and purification of lignosulfonates from spent sulfite liquor was established.

Factors influencing antibiotics adsorption onto engineered adsorbents

The study evaluated the adsorption of two antibiotics by four engineered adsorbents (hypercrosslinked resin MN-202, macroporous resin XAD-4, activated carbon F-400, and multi-walled carbon nanotubes (MWCNT)) from aqueous solutions. The dynamic results demonstrated the dominant influence of pore size in adsorption. The adsorption amounts of antibiotics on XAD-4 were attributed to the hydrophobic effect, whereas steric hindrance or micropore-filling played a main role in the adsorption of antibiotics by F-400 because of its high microporosity. Aside from F-400, similar patterns of pH-dependent adsorption were observed, implying the importance of antibiotic molecular forms to the adsorption process for adsorbents. Increasing the ionic concentration with CaC12 produced particular adsorption characteristics on MWCNT at pH 2.0 and F-400 at pH 8.0, which were attributed to the highly available contact surfaces and molecular sieving, respectively. Its hybrid characteristics incorporating a considerable portion of mesopores and micropores made hypercross linked MN-202 a superior antibiotic adsorbent with high adsorption capacity. Furthermore, the adsorption capacity of MWCNT on the basis of surface area was more advantageous than that of the other adsorbents because MWCNT has a much more compact molecular arrangement.

Study on adsorption and desorption properties of the starch grafted p-tert-butyl-calix[n]arene for butyl Rhodamine B solution

The adsorbents of starch grafted p-tert-butyl-calix[4,6,8]arene-SGCn (SGC4, SGC6, SGC8) are prepared. The products are characterized by FTIR, elemental analysis, thermal gravimetric analysis and scanning electron microscope. Static adsorption behavior is studied by using SGC8 as adsorbent, butyl Rhodamine B (BRB) solution as simulation dye wastewater. The adsorption of BRB onto SGC8 fits the second order kinetic model and the apparent adsorption rate constant is 0.002 g mg(-1)min(-1) at 25 °C. The equilibrium adsorption data are interpreted using Langmuir and Freundlich models. The adsorption of BRB onto SGC8 is better represented by the Langmuir equation. The thermodynamic parameters for the adsorption reaction are calculated through van't Hoff analysis. The adsorbent may be easily regenerated by using ethanol solution as desorption agent to extract dye from SGC8. The rate of desorption of BRB is dependent on the concentration of ethanol and the temperature. SGC8 exhibits excellent adsorption and desorption properties toward dye molecule. The new-style adsorbent of SGC8 is regarded as a potential adsorbent to deal with dye or organic wastewater.

Functional Groups and Interactions Controlling the Adsorption of Bisphenol a onto Different Polymers

The behaviour of different polymers in the adsorption and removal of bisphenol A (BPA) from aqueous solutions was examined in order to identify the mechanism controlling the process. Three polymers with different functional groups were prepared and employed in our laboratory; they were characterized both texturally and chemically in terms of their surface areas, pore-size distributions, total exchange capacities and other parameters. The adsorption isotherms of bisphenol A were obtained and accurately modelled by the three-parameter Langmuir–Freundlich (LF) isotherm, the binding parameters calculated directly by the LF fitting coefficients indicating that increasing temperature was helpful in causing the adsorption process to move from positive cooperativity to negative cooperativity.

The kinetic data were found to be well represented by the pseudo-second-order kinetic model, indicating that the functional groups of the polymers had a significant influence on the adsorption mechanism of BPA. The adsorption of BPA basically depended on the chemical nature of the polymers and the pH value of the solution. The adsorption process was favoured by the molecular form of bisphenol A, since this controlled the surface complexes produced between the polymer surface and the bisphenol A molecules, with the resulting increase in adsorbent–adsorbate interactions being positively influenced by the temperature.