RESUMO
The significant environmental issue of water pollution caused by emerging contaminants underscores the imperative for developing novel cleanup methods that are efficient, economically viable, and that are intended to operate at high capacity and under continuous flows at the industrial scale. This study shows the results of the operational design to build a prototype for the retention at lab scale of pollutant residues in water by using as adsorbent material, insoluble polymers prepared by ß-cyclodextrin and epichlorohydrin as a cross-linking agent. Laboratory in-batch tests were run to find out the adsorbent performances against furosemide and hydrochlorothiazide as pollutant models. The initial evaluation concerning the dosage of adsorbent, pH levels, agitation, and concentration of pharmaceutical pollutants enabled us to identify the optimal conditions for conducting the subsequent experiments. The adsorption kinetic and the mechanisms involved were evaluated revealing that the experimental data perfectly fit the pseudo second-order model, with the adsorption process being mainly governed by chemisorption. With KF constant values of 0.044 (L/g) and 0.029 (L/g) for furosemide and hydrochlorothiazide, respectively, and the determination coefficient (R2) being higher than 0.9 for both compounds, Freundlich yielded the most favorable outcomes, suggesting that the adsorption process occurs on heterogeneous surfaces involving both chemisorption and physisorption processes. The maximum monolayer adsorption capacity (qmax) obtained by the Langmuir isotherm revealed a saturation of the ß-CDs-EPI polymer surface 1.45 times higher for furosemide (qmax = 1.282 mg/g) than hydrochlorothiazide (qmax = 0.844 mg/g). Based on these results, the sizing design and building of a lab-scale model were carried out, which in turn will be used later to evaluate its performance working in continuous flow in a real scenario.
Assuntos
Ciclodextrinas , Poluentes Químicos da Água , Purificação da Água , Água , Furosemida , Poluentes Químicos da Água/química , Purificação da Água/métodos , Polímeros/química , Adsorção , Cinética , Hidroclorotiazida , Concentração de Íons de HidrogênioRESUMO
Water pollution by dyes is a huge environmental problem; there is a necessity to produce new decolorization methods that are effective, cost-attractive, and acceptable in industrial use. Magnetic cyclodextrin polymers offer the advantage of easy separation from the dye solution. In this work, the ß-CD-EPI-magnetic (ß-cyclodextrin-epichlorohydrin) polymer was synthesized, characterized, and tested for removal of the azo dye Direct Red 83:1 from water, and the fraction of non-adsorbed dye was degraded by an advanced oxidation process. The polymer was characterized in terms of the particle size distribution and surface morphology (FE-SEM), elemental analysis (EA), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), infrared spectrophotometry (IR), and X-ray powder diffraction (XRD). The reported results hint that 0.5 g and pH 5.0 were the best conditions to carry out both kinetic and isotherm models. A 30 min contact time was needed to reach equilibrium with a qmax of 32.0 mg/g. The results indicated that the pseudo-second-order and intraparticle diffusion models were involved in the assembly of Direct Red 83:1 onto the magnetic adsorbent. Regarding the isotherms discussed, the Freundlich model correctly reproduced the experimental data so that adsorption was confirmed to take place onto heterogeneous surfaces. The calculation of the thermodynamic parameters further demonstrates the spontaneous character of the adsorption phenomena (ΔG° = −27,556.9 J/mol) and endothermic phenomena (ΔH° = 8757.1 J/mol) at 25 °C. Furthermore, a good reusability of the polymer was evidenced after six cycles of regeneration, with a negligible decline in the adsorption extent (10%) regarding its initial capacity. Finally, the residual dye in solution after treatment with magnetic adsorbents was degraded by using an advanced oxidation process (AOP) with pulsed light and hydrogen peroxide (343 mg/L); >90% of the dye was degraded after receiving a fluence of 118 J/cm2; the discoloration followed a pseudo first-order kinetics where the degradation rate was 0.0196 cm2/J. The newly synthesized ß-CD-EPI-magnetic polymer exhibited good adsorption properties and separability from water which, when complemented with a pulsed light-AOP, may offer a good alternative to remove dyes such as Direct Red 83:1 from water. It allows for the reuse of both the polymer and the dye in the dyeing process.
Assuntos
Compostos Azo , Poluentes Químicos da Água , Adsorção , Compostos Azo/química , Corantes/química , Concentração de Íons de Hidrogênio , Cinética , Fenômenos Magnéticos , Polímeros , Termodinâmica , Águas Residuárias , Água/química , Poluentes Químicos da Água/químicaRESUMO
Due to the negative effects of emerging contaminants on the environment, that can potentially induce deleterious effects in aquatic and human life, this paper focuses on the removal from the water of Furosemide, through the adsorption process. Indeed, only a few papers are available in the literature about the Furosemide adsorption and, chitosan films are thus proposed for this purpose as safe, sustainable, and recyclable adsorbent materials. In the present work, the effects on the adsorption process of several experimental parameters such as the pH values, ionic strength, amount of adsorbent/pollutant, and temperature values were investigated. The kinetics models, isotherms of adsorption, and the thermodynamic parameters were studied showing that the Furosemide physisorption occurred on the heterogeneous Chitosan surface, endothermically (ΔH° = +31.27 ± 3.40 kJ mol-1) and spontaneously (ΔS° = +150.00 ± 10.00 J mol-1 K-1), following a pseudo-second-order kinetic model. The 90% of the pollutant was adsorbed in 2 h, with a maximum adsorption capacity of 3.5 mg × g-1. Despite these relatively low adsorption capacities, experiments of desorption were performed and 100% of adsorbed Furosemide was recovered by using concentrated NaCl solutions, proposing a low-cost and green approach, with respect to the previous literature relative to the Furosemide adsorption, fundamental for the pollutant recovery and adsorbent reuse.
Assuntos
Quitosana/química , Furosemida/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Humanos , Concentração de Íons de Hidrogênio , Cinética , Temperatura , TermodinâmicaRESUMO
Water pollution caused by dyes is a significant environmental issue, necessitating the development of effective, cost-efficient decolorization methods suitable for industrial use. In this study, a Chitosan-Fe polymeric gel was synthesized, characterized, and tested for removing the azo dye Direct Red 83:1 from water. The polymeric magnetic chitosan was analyzed using various techniques: Field Emission Scanning Electron Microscopy (FE-SEM) revealed a porous structure, Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA) demonstrated the thermal stability, Infrared Spectrophotometry (IR) indicated the successful coordination of iron at the C3 position, and X-ray Powder Diffraction (XRD) confirmed the crystalline nature of the polymeric structure. Optimal conditions for kinetic and isotherm models were found at 1 g and pH 7.0. Adsorption behavior of Direct Red 83:1 onto magnetic chitosan gel beads was studied through kinetic tests and isotherm curves. The maximum adsorption capacity was 17.46 mg/g (qmax). The adsorption process followed pseudo-second-order kinetics (R2 = 0.999) and fit the Temkin isotherm (R2 = 0.946), suggesting heterogeneous surface adsorption. The newly synthesized Chitosan-Fe polymeric gel demonstrated good adsorption properties and facilitated easy separation of purified water.
RESUMO
This study is aimed to validate water-insoluble cyclodextrin-epichlorohydrin polymer (ß-EPI) use to remove, by adsorption, sulfamethoxazole (SMX) from water and then release it via an environmentally friendly treatment so that the adsorbent can be recycled according to one of the objectives of the European Project Life "Clean up" (LIFE 16 ENV/ES/000169). SMX adsorption experiments on ß-EPI polymer in-batch were performed, varying different experimental parameters of the process, such as contact time, pH values, and so on. The adsorption process, exothermic and driven by enthalpy, occurs both through the formation of inclusion and association complexes, involves mainly hydrophobic and hydrogen bonds, has a rate-controlling step depending on both pollutant concentration and adsorbent dose and can be described by the Freundlich and Dubinin-Radushkevich models which confirm the polymer surface heterogeneity and the physical nature of the adsorption. The presence of salts gives rise to a general decrease in the SMX sorption, mainly in the case of bromide, which was used to promote the SMX desorption and regenerate the adsorbent. The overall results indicate that ß-EPI polymer is not only capable of removing SMX by adsorption with short contact times and a qmax = 10 mg/g but it is also easily regenerated using a 0.5 M solution of sodium bromide without any loss in the adsorption performance and with obvious economic and environmental advantages. The polymer as synthesized, with SMX adsorbed and regenerated was characterized by FT-IR, SEM and DSC.
Assuntos
Ciclodextrinas , Poluentes Químicos da Água , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Sais , Espectroscopia de Infravermelho com Transformada de Fourier , Sulfametoxazol , Água , Poluentes Químicos da Água/análiseRESUMO
This paper focuses on the removal of tetracycline from polluted water by chitosan-olive pomace adsorbing films. More specifically, both raw olive solid wastes (olive pomace) and the olive solid wastes/chitosan composite were compared and used for this purpose. Adsorption capacities values of 16â¯mgâ¯×â¯g-1 and 1.6â¯mgâ¯×â¯g-1 were obtained for the two adsorbents respectively. However, chitosan/olive pomace is proposed as suitable for environmental applications avoiding the dispersion of the pomace blocked inside the chitosan film. To detail the adsorption process, the effect of several experimental parameters such as the pH values, ionic strength, amount of adsorbent and pollutant and temperature values was investigated. The results showed that the adsorption process improved increasing the pH values, with a maximum at pHâ¯8, and it was negatively affected by the presence of salts that retarded the adsorption. Indeed, the desorption of tetracycline was obtained in a MgCl2 2â¯M solution. So, a low-cost and cleaner approach, fundamental for the pollutant recovery and for an adsorbent safe reuse, for several cycles of adsorption/desorption, transforming a waste in resource is presented. The kinetics, isotherms models of adsorption and the thermodynamic parameters (ΔG°, ΔH° and ΔS°) were also evaluated observing that the physisorption of the pollutant occurred with and an endothermic character (ΔH°â¯>â¯0) with ΔG°â¯<â¯0 and ΔS°â¯>â¯0. The use of Advanced Oxidation Processes was proposed as possible alternative to the tetracycline recovery, obtaining its degradation after the desorption. With the present paper, the alternative reuse of olive pomace is reported avoiding its disposal in the environment claiming its potential in the removal/recover of emerging contaminants from water.