Synthesis, adsorption and molecular simulation study of methylamine-modified hyper-cross-linked resins for efficient removal of citric acid from aqueous solution

Abstract

A series of methylamine-modified hyper-cross-linked resins were fabricated from chloromethylated polystrene-co-divinylbenzene by two continuous reactions (Friedel-Crafts alkylation and amination). the Bet surface area and pore volume of the as-prepared resins took a positive correlation to the reaction time and temperature during alkylation reaction while lessened during amination process. When running batch adsorption experiments for adsorption of citric acid, the methylamine-modified resin named HM-65-2 showed higher adsorption capacity of 136.3 mg/g and selectivity of 6.98 (citric/ glucose) than the precursor resins. The pseudo-second-order rate model fitted better than the pseudo-first-order model, implying the adsorption sites distributed on the resins surface tended to be heterogeneous. Subsequently, the interactions between citric acid and the resin were investigated by means of molecular simulation. Simulation result showed the addition of nitrogen-containing groups significantly enhanced the adsorption performance of citric acid. Lastly, the dynamic column experiments were performed to obtain the suitable operating conditions for the citric acid adsorption. Citric acid (CA, 2-hydroxypropane-1,2,3-tricarboxylic acid, C 6 H 8 O 7), as an important organic acid associated with thermoplastics fields in virtue of versatility, plays multiple roles in food, pharmaceutical, chemical or bio-processing industry etc. due to its favorable physico-chemical properties 1. Citric acid is mainly manufactured by the fermentation of carbohydrates by Aspergillus niger using submerged processes, which is relatively easy to achieve high yield and environmental friendly product 2. However, the recovery of citric acid from the fermentation broth is not straightforward. The conventional separation technique used in industry includes several batch steps increasing the production cost and generating a considerable amount of environmentally harmful waste 3. Some novel separation techniques, i.e., solvent extraction 4 , electro-dialysis 5 , membrane separation 6 , ion exchange 7 and adsorption 8 have been proposed for citric acid recovery and purification, among which adsorption has been considered to be one of the most efficient and simple method due to its wide application scope, energy-saving, and environmentally friendly. Most adsorbents selected for recovering citric acid are based on weak-base ion-exchangers 9 , which needs some harsh desorption conditions i.e. alkaline solutions and limits its practical application. Gluszcz et al. 10 studied the adsorption behaviors of different ion exchange resins for citric acid recovery from aqueous solutions and ascertained that the resin with a tertiary amine functional group was suitable for citric acid recovery. Juang et al. 11 explored the adsorption behaviors of citric acid on macroporous resins impregnated with tri-n-octylamine. Other adsorbents including hydroxyapatite 12 , oxides 13 and chitosan

A review on adsorbent parameters for removal of dye products from industrial wastewater

“…This may be due to the increment of the mobility of dye molecules, as the number of active sites for adsorption increases with increasing the process temperature (Wong et al 2020). On the other hand, there are several adsorption processes in which increases in temperature adsorption capacity have declined, indicating the exothermic adsorption process (Belhamdi et al 2016;Peng et al 2020;Romdhane et al 2020). In this kind of adsorption, the adsorption forces between the dye species and the active sites on the adsorbent surface decreased, resulting in a decrease in the adsorption process.…”

An Overview of Heterogeneous Catalysts Based on Hypercrosslinked Polystyrene for the Synthesis and Transformation of Platform Chemicals Derived from Biomass

“…The authors attribute the high selectivity of HCPMOS towards iron cations to their stronger interactions with methoxy groups as compared to cations of other metals. A number of methylamine-modified hypercrosslinked resins have been proposed for the selective sorption of citric acid [67]. During the periodic sorption of citric acid, the methylamine-modified HM-65-2 resin showed a high adsorption capacity (136.3) mg/g and a selectivity of 6.98 (citric acid/glucose), which makes this sorbent a promising candidate for the purification of citric acid and further use in the separation process with simulating a moving bed (SMB).…”

Citric Acid Recovery and Methanol Production from a Waste Food Fruit Sample by Thermal Decomposition of a Reusable Zinc Citrate Complex

“…As an alternative, various methods for the separation and purification of CA have recently been developed, for example, liquid–liquid extraction and reactive extraction (amines dissolved in various diluents). − Nevertheless, the precipitation method is still predominantly used on a large scale for the production of CA, which converts the crude CA from the fermentation broth. The most promising route is addressed by the Kimi method, in which CA is recovered by using calcium hydroxide, followed by the ion exchange process.…”