Desorption Solution Research Articles

Exploiting the Different Parameters on the Adsorption of Phosphate Ions and Its Subsequent Recovery Using Complex Nickel-Aluminum-Zirconium Hydroxide.

In this study, the effect of contact time, temperature, pH, and coexistences on the adsorption of phosphate ions using the complex nickel-aluminum-zirconium hydroxide (NAZ) was evaluated. Moreover, the recovery of adsorbed phosphate ions from NAZ using desorption solution with different concentrations was demonstrated. The results showed that the quantity of phosphate ions adsorbed gradually increased with time, and the adsorption equilibrium was achieved within 24 h after adsorption. This kinetic data could be well described by the pseudo-second-order model with the correlation coefficient in the value of 0.997. Additionally, the quantity of phosphate which was adsorbed increased as temperature increased, and these results corresponded well with both the Langmuir, the correlation coefficient ranged from 0.920-0.949, and Freundlich models, the correlation coefficient ranged from 0.863-0.995. These results showed that the adsorption of phosphate ion was monolayer adsorption onto the NAZ surface. The optimal pH for removal of phosphate ions from aqueous media was during 4-8. In addition, chloride, nitrate, and sulfate ions did not significantly affect to the adsorption capability of phosphate ions in the complex solution system. Finally, the phosphate ions which were adsorbed onto NAZ could be recovered using sodium sulfate solution (recovery percentage: approx. 50% using sodium sulfate solution at 1000 mmol/L). These results highlight the potential of using NAZ as the cost-effectiveness adsorbent for phosphate ions removal from aqueous media.

Facile preparation of nano-g-C3N4/UiO-66-NH2 composite as sorbent for high-efficient extraction and preconcentration of food colorants prior to HPLC analysis

In this work, the nano-g-C3N4/UiO-66-NH2 composite was prepared by one-step solvothermal method. The as-prepared composite was characterized by scanning electron microscopy, Brunner-Emmet-Teller measurement, energy dispersive spectrometer, X-ray diffraction, and Fourier transform infrared spectroscopy. By using nano-g-C3N4/UiO-66-NH2 composite as sorbent, a dispersive solid-phase extraction coupled with high-performance liquid chromatography was developed to sensitive analysis of food colorants including tartrazine, amaranth, carmine, sunset yellow, allura red and bright blue. The experiment parameters including the amount of sorbent, adsorption time, the pH of adsorption solution, desorption time, desorption solvent, the pH of desorption solution as well as the proportion between desorption solvent and buffer solvent were investigated. Under the optimized conditions, the limits of detection (S/N = 3) and limits of quantitation (S/N = 10) were determined in the ranges of 0.08–0.8 and 0.2–2.0 ng/mL, respectively. With the developed sample pretreatment method, carmine and brilliant blue were determined from blueberry juice by HPLC-DAD. The contents were calculated as 1.53 µg/mL and 0.17 µg/mL, respectively.

Fe-based layered double hydroxides for removing arsenic from water: sorption-desorption-regeneration.

Since the presence of arsenic in the waters of the world causes serious health effects on people, it is very important to remove it. Layered double hydroxides have a high surface area and high anion exchange capacity, and because of this feature, it is a potential adsorbent to remove arsenic. For regeneration and reuse of adsorbents, researchers in some limited studies have used agents such as acids and alkalis. Media replacement accounts for approximately 80% of the total operational and maintenance costs. In this paper, an adsorption/desorption/regeneration study was carried out with MgFeHT to determine the desorption properties of the adsorbent and to examine its reusability. The best alkaline desorption solution was determined from two different alkaline solutions: NaOH and KH2PO4. As(V) adsorption capacity of the MgFeHT at different pH (3-12) using the arsenic aqueous solution (with 2,000 μg As(V)/L) was evaluated. For the adsorption process, the experimental data are fitted well with the pseudo-second-order kinetic model and the Langmuir model. Moreover, the concentration of 2,000 μg/L arsenic was reduced to below the legal limit determined by the WHO (<10 μg/L). The regeneration studies were conducted on the adsorptive media used in the arsenic removal system. The regeneration efficiency of As(V) was maintained 98.5% for four regeneration cycles using 0.5 M NaOH. MgFeHT was successfully regenerated with an aqueous solution of NaOH and was reused with a small loss of sorption efficiency.

A solid-phase microextraction fiber coating based on magnetic covalent organic framework for highly efficient extraction of triclosan and methyltriclosan in environmental water and human urine samples

Herein, we synthesized a kind of magnetic covalent organic framework nanohybrids (NiFe2O4@COF), and integrated it with polydimethyl siloxane and silicone rubber curing agent for solid phase microextraction (SPME) fiber coating. The fiber coating demonstrated a porous and uniform surface with the BET specific surface of 169.7 m2 g-1. As for seven environmental analytes, the NiFe2O4@COF-based SPME fiber coating gave the higher extraction recoveries for triclosan (TCS) and methyltriclosn (MTCS) than those of fenpropathrin, bifenthrin, permethrin, fenvalerate and deltamethrin. Several operational parameters were rigorously optimized, such as extraction temperature, extraction time, thermal desorption time, solution pH and salt effect. Combined with the GC-ECD detection, the newly developed microextraction method supplied the wide linear range of 0.1–1000 µg L-1 with the correlation coefficients of > 0.9995. The limits of detection (LODs) and limits of quantitation (LOQs) reached as low as 1–7 ng L-1 and 3.3–23 ng L-1, respectively. The intra-day and inter-day precisions in six replicates (n = 6 ) were < 3.55% and < 5.06%, respectively, and the fiber-to-fiber reproducibility (n = 3) was < 7.64%. To evaluate its feasibility in real samples, the fortified recoveries for TCS and MTCS, at low (0.2 µg L-1), middle (2.0 µg L-1) and high (20.0 µg L-1) levels, varied between 81.9% and 119.1% in tap, river and barreled waters as well as male, female and children urine samples. Especially, it is worth mentioning that the NiFe2O4@COF-based SPME coating fiber can be recycled for at least 150 times with nearly unchanged extraction efficiency. Moreover, the extraction recoveries by the as-fabricated fiber coating were much higher than those by three commercial fibers (PDMS, PDMS/DVB and PDMS/DVB/CAR). Overall, the NiFe2O4@COF-based SPME is a convenient, sensitive, efficient and “green” pretreatment method, thereby possessing important application prospects in trace monitoring of TCS-like pollutants in complex liquid matrices.

Tween 20-capped gold nanoparticles for selective extraction of free low-molecular-weight thiols in saliva followed by capillary electrophoresis with contactless conductivity detection

Low-molecular-weight thiols are widely present in human fluids, and are regarded as a kind of potential broad-spectrum evaluation indicators for some clinical diseases. In this work, gold nanoparticles capped with Tween 20 were used for purification and microextraction of the main free thiols (cysteine, homocysteine, glutathione and methionine) in saliva based on Au-S bond formation. Ultrasound further sped up the releasing of the target analytes, and the releasing time needed was only 10 min, and the required sample volume was only 40 µL. The desorption solution could be directly injected for electrophoretic analysis without derivatization, and field-amplified sample stacking of electrophoretic online enrichment technology further improved the detection sensitivity. The synergistic enrichment effect made the enrichment factors of four analytes reach 1119–2067 times. This developed method was applied for the analyses of saliva samples of healthy volunteers. Acceptable sensitivity (LODs: 0.15–1.5 ng mL−1) and recoveries (97.6–116%) were obtained in the saliva sample matrix. This proposed method provides an alternative for the sensitive detection of low-molecular-weight thiols in noninvasive body fluids, which has potential application prospect in the preliminary noninvasive diagnosis of diabetes, cardiovascular diseases, etc.

High-throughput biomonitoring of organophosphate flame-retardant metabolites in urine via 96-blade solid-phase microextraction coupled with ultra-performance liquid chromatography-tandem mass spectrometry

Organophosphate flame retardants (OPFRs) are widely used in consumer products and building materials, but their propensity for migration poses a problem with respect to polluting indoor environments, water, soil, and dust. OPFR metabolites in urine samples are appropriate biomarkers for assessing exposure risk levels. In this paper, a high-throughput method that couples 96-blade solid-phase microextraction with ultra-performance liquid chromatography-tandem mass spectrometry (SPME-UPLC-MS/MS) is applied for the simultaneous detection of four OPFR metabolites in urine samples. The results indicated that the best extraction was achieved using 96 blades coated with hydrophilic-lipophilic balance weak anion exchange (HLB-WAX). The proposed SPME method's extraction efficiency was maximized by optimizing extraction time, pH value, desorption solution, desorption volume, and desorption time, and it was validated in accordance with the Food and Drug Administration's guidelines. The findings indicated that the proposed method has a wide linearity range (0.5–100 ng mL−1) and low detection limits (0.09–0.14 ng mL−1). The method's accuracy ranged from 98% to 118%, with intra-day precision ranging from 1% to 10%. In contrast, inter-day precision ranged from 3% to 16%. Accuracy was also evaluated using independent urine samples, which ranged from 78% to 124% with corresponding relative standard deviations (1%–16%). Ultimately, DoCP was detected in two real samples at a concentration of 0.5–1.1 ng mL−1, and BEHP was detected at a concentration of 0.2–1.2 ng mL−1. Overall, the proposed SPME-UPLC-MS/MS method is reliable, accurate, and capable of simultaneously determining four OPFR metabolites in urine samples and screening them to assess exposure risk for humans.

Adsorption and Desorption Behaviors of Antibiotics on TWP and PVC Particles Before and After Aging

In recent years, microplastics (MPs), a new type of pollutant, have been widely dispersed in aquatic ecosystems. Compared with typical MPs (PVC, PP, PE, and PS), tire wear particles (TWP) exhibit significant differences in composition, additives, and characteristics. In this study, the adsorption and desorption of organic pollutants were compared between the typical MPs and TWP. With TWP and polyvinyl chloride (PVC) particles as adsorbents, oxytetracycline (OTC) and sulfamethoxazole (SMZ) as adsorbates, the adsorption and desorption of organic pollutants by TWP and PVC particles before and after aging were studied. Correctly understanding the behavior of MPs in an aquatic environment is of great significance. The results indicated that during the UV aging process, both TWP and PVC exhibited cracks, pits, and bulges on the particle surface, increased specific surface areas, increased strength of oxygen-containing functional groups, and enhanced hydrophilicity. The adsorption modes of TWP and PVC before and after aging were in two stages:surface adsorption and liquid film diffusion. TWP has a better fit for the Freundlich model, belonging to multi-layer adsorption, while PVC has a better fit for the Langmuir model, belonging to monolayer adsorption. The carrier effect of TWP on antibiotics was better than that of PVC, with the adsorption capacity of OTC on virgin TWP and PVC reaching 5.14 mg·g-1 and 1.38 mg·g-1, respectively. Additionally, the adsorption capacity of OTC on the aged TWP and PVC reached 5.82 mg·g-1 and 2.13 mg·g-1, respectively, which was better than with the virgin samples. The desorption capacity of aged TWP and PVC for antibiotics was better than the virgin materials, while the desorption rate was lower. In the same desorption solution, the desorption effect of TWP on antibiotics before and after ageing was better than that of PVC. The desorption effect of TWP and PVC on antibiotics in a simulated intestinal fluid environment was significantly better than that in an ultra-pure water environment.

Highly Selective Adsorption and Desorption of Charged Molecules in Three-Dimensional Networks of Polydopamine-Modified Carbon Nanotube Sponges.

We investigated the selective adsorption and desorption behaviors of charged molecules (calcein, brilliant green, and methylene blue) dissolved in water using polydopamine-modified carbon nanotube (CNT) sponges. Porous CNT sponges (CNTSs) as a scaffold for the selective adsorption and desorption of aqueous molecules were fabricated by using a chemical vapor deposition technique. To improve the hydrophilicity of porous CNTS and to control the adsorption and desorption of aqueous molecules, CNT sidewalls were decorated with a hydrophilic polydopamine layer through noncovalent interactions between CNT sidewalls and polydopamine. After this noncovalent chemical modification, the water contact angle of CNTS was close to 0, and the aqueous solution can rapidly infiltrate the three-dimensional (3D) networks of polydopamine-modified CNTS (Pdop-CNTS). The incorporation of pH-responsive polydopamine in CNTS showed an evident advantage of adsorbing positively charged molecules over a pH range of 10.5-4. In aqueous solutions with pH value of ≤3, Pdop-CNTS selectively adsorbed negatively charged molecules. Aqueous molecules carrying net charges were successfully separated from mixture solutions. Moreover, charged calcein and methylene blue molecules adsorbed on the 3D networks of Pdop-CNTS were selectively desorbed from Pdop-CNTS by tuning the pH value of the desorption solution.

Polyethyleneimine-functionalized Fe3O4/attapulgite particles for hydrophilic interaction-based magnetic dispersive solid-phase extraction of fluoroquinolones in chicken muscle.

Fluoroquinolone (FQ) residues in foods of animal origin may threaten public health but are challenging to determine because of their low contents and complex matrices. In this study, novel polyethyleneimine-functionalized Fe3O4/attapulgite magnetic particles were prepared by a simple co-mixing method and applied as hydrophilic sorbents for the magnetic dispersive solid-phase extraction (MSPE) of three FQs, i.e., ciprofloxacin, norfloxacin, and enrofloxacin, from chicken muscle samples. The preparation of the magnetic particles was of high reproducibility and the products could be reused many times with high adsorption capacity. The key experimental factors possibly influencing the extraction efficiencies, including sample solution, extraction time, sample loading volume, desorption solution, desorption time, and elution volume were investigated. Under optimum MSPE conditions, the analytes in chicken muscle samples were extracted and then determined by RPLC-MS/MS in MRM mode. Good linearity was obtained for the analytes with correlation coefficients ranged from 0.9975 to 0.9995. The limits of detection were in the range of 0.02-0.08μgkg-1, and the recoveries of the spiked FQs in chicken muscle samples ranged from 83.9 to 98.7% with relative standard deviations of 1.3-6.8% (n = 3). Compared with the traditional MSPE methods based on hydrophobic mechanism, this hydrophilic interaction-based method significantly simplifies the sample pretreatment procedure and improves repeatability. This method is promising for accurate monitoring of FQs in foods of animal origin.

Behaviors of Desorption Agents During Removal of Cs From Clay Minerals and Actual Soil

The behaviors of various desorption agents were investigated during the desorption of cesium (Cs) from samples of clay minerals and actual soil. Results showed that polymeric cation exchange agents (polyethyleneimine (PEI)) efficiently desorbed Cs from expandable montmorillonite, whereas acidic desorption solutions containing HCl or PEI removed considerable Cs from hydrobiotite. However, most desorption agents could desorb only 54% of Cs from illite because of Cs’s specific adsorption to selective adsorption sites. Cs desorption from an actual soil sample containing Cs-selective clay mineral illite ( PEI > NH4+, and the highest Cs desorption amount achieved using HCl was 83%. Unlike other desorption agents with only cation exchange capabilities, HCl can attack minerals and induce dissolution of metallic elements. HCl’s ability to both alter minerals and induce H+/Cs+ ion exchange is expected to promote Cs desorption from actual soil samples.

Determination of o-toluidine in workplace air by solvent desorption-gas chromatography

To establish solvent desorption gas chromatograph method for o-toluidine determination in workplace air. The o-toluidine vapour in workplace air was collected with silicone tube, and desorbed with absolute ethanol. Then the desorption solution was separated with polyethylene glycol HP-INNOWax capillary column(30 m×0. 32 mm, 0. 50 μm)and measured with flame ionization detector. Detection limit of the method was 0. 18 μg/mL, quantification limit of the method was 0. 60 μg/mL, quantitative determination range of method was 0. 60-245. 37 μg/mL, and the minimum quantitative determination concentration was 0. 20 mg/m~3(based on 3. 0 L sample). The method had a good reproducibility, the relative standard deviation was 1. 0%-3. 5%, the average of desorption efficiency was 98. 7%, and the average of sampling efficiency was 93. 7%. The penetrating capacity of 200 mg alkaline silicone was over than 2. 1 mg, and the samples at room temperature could be preserved for 15 days at least. Methanol, toluene, chlorobenzene, acetoacetic ester, aniline, N-methylaniline, N, N-dimethylaniline, o-nitroaniline, p-toluidine or m-toluidine coexisted in the air did not interfere during the determination of o-toluidine. The method with low determination concentration, high accuracy and precision, is feasible for determination of o-toluidine vapour in workplace air.

Detection and Neutralization of Unsymmetrical Dimethylhydrazine on the Surface of Construction Materials

The construction materials that contacted with unsymmetrical dimethylhydrazine and the desorption solutions obtained when treating the contaminated surface of metals and alloys with water and reagents were studied by chromatography and mass spectrometry. Neutralization of unsymmetrical dimethylhydrazine was studied using ozone and shungite. Ozonation makes it possible to destroy the toxicant molecules chemically and physically adsorbed on the surface of metal constructions, due to which they can be reused and utilized. Shungite effectively adsorbs and catalytically decomposes not only unsymmetrical dimethylhydrazine and its transformation products, but also oligomer compounds formed during the storage of hydrazine fuel. Ozonation of spent shungite can increase the efficiency of destructive processes and completeness of its regeneration.

Optimization of purification conditions for areca seeds using microporous resins

As a synthetic macroporous polymer adsorbent, resin can selectively adsorb the target components in water and nonwater systems through electrostatic force, hydrogen bond, and complexation to achieve the separation and purification of substances. Moreover, it is easy to regenerate and can be repeatedly used. Macroporous resins exhibit high adsorption capacity toward organic molecules and have been widely used in the separation and purification of bioactive substances. Polyphenols obtained from areca seed extracts exhibit high antioxidant properties. Herein, the ability of AB-8, NKA-9, A-8, X-5, and XAD-75 macroporous resins to purify polyphenols obtained from betel nut seeds was evaluated and compared. The adsorption mechanism was described using the Langmuir and Freundlich equations, and the purification parameters were optimized using adsorption–desorption experiments. To determine the purity of each component, the polyphenol content in the five macroporous resins was analyzed. Results show that the initial concentration of polyphenols was 3.0 mg/mL, pH was 3.0, the concentration of ethanol desorption solution was 50% (V/V), and the flow rate of elution was 2 mg/mL after purification using XAD-7. The purified products obtained using XAD-7 exhibited a stronger antioxidant activity than those obtained using the other four macroporous resins.

Removal and Release of the 2,4,5-Trichlorophenoxyacetic Acid Herbicide from Wastewater by Layered Double Hydroxides

The Zn2–Al layered double hydroxides (LDHs) have been used to remove the 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) herbicide, which is used as a model for pesticides from the carboxylate family. The adsorption isotherms are governed by Langmuir model (L type). The characterization by various techniques (XRD, FTIR, SEM) indicates that the 2,4,5-T retention is governed by adsorption on the sites of the LDH surface when the molar ratio 2,4,5-T/Cl ≤ 0.1. For greater ratio values, the herbicide undergoes, in addition, intercalation in the LDH interlayer domain leading to an increase of the interlayer distance from 0.778 to 1.855 nm. The retention capacity reaches 718 mg/g with a removal rate of 96% for an optimal 2,4,5-T/Cl molar ratio of 0.5. This capacity is influenced by the solution pH, the charge density of the LDH sheets, the adsorbent/adsorbate molar ratio and the nature of the interlayer anion of the LDH precursor. The partial or total release of the herbicide was observed to depend on the composition of the desorbing solution. This suggests the possibility of LDH recycling and confirms thus its effectiveness in eliminating this type of pollutant from water. In addition, a well-structured [Zn2–Al-2,4,5-T] hybrid material was obtained after herbicide retention and its characterization by chemical analyses and SEM as well as a proposed structural model are presented.

Phosphate recovery from sewage sludge supernatants using magnetic nanoparticles

Phosphorus removal and recovery from synthetic solutions and sewage sludge supernatants by using magnetic nanoparticles (MNP) were investigated through batch adsorption experiments. The adsorption kinetics and isotherms on the removal of phosphate have been studied using different MNP doses, contact time, pH, and initial P concentrations. Reusability of the MNP and the enrichment of phosphate in desorption solution from dewatering supernatants were tested in a series of adsorption-desorption cycles. The removal efficiency was between 29 and 97 % after 24 h depending on the P concentrations and adsorbent concentrations. This efficiency was detectable in pH ∼ 3–5 but decreased in case of increased pH levels. Intra particle (IP) diffusion model kinetic tests demonstrated that the adsorption process was controlled by a multi-step mechanism and the reaction equilibrium was reached after 120 min. Besides phosphate, ammonium, magnesium and calcium ions were adsorbed on MNP to a lesser extent. Surface characterization and adsorption mechanism were discussed based on XRD, SEM and FTIR analyses. MNP can be very effective for both ammonia and phosphate removal and recovery from dewatering supernatant solutions.

Desorption characteristics of phosphate and ammonium from sludge-based biochar

ABSTRACT It is effective to adsorb phosphate and ammonium from water by sludge-based biochar, while the desorption performance has not been studied systematically. Biochar in this study was prepared through the co-pyrolysis of sludge and walnut shells to remove and from water. The desorption characteristics of and from the post-adsorption sludge-based biochar were investigated. The effects of the adsorption condition (concentration of adsorption solution) and desorption conditions (pH value of desorption solution and desorption temperature and time) on desorption performance were examined. Several techniques were performed to characterise the properties of the post-adsorption sludge-based biochar. The adsorption amount of the pure sewage sludge biochar (SBC) for and the biochar derived from the co-pyrolysis of sewage sludge and walnut shell with the mixing ratio of 3:1 (MBC3-1) for were 14.19/ 23.75 mg/g and 9.28/ 16.23 mg/g, respectively, when the concentrations of the adsorbates were 100 and 500 mg/L. The desorption experiments showed that the acidic condition (pH = 2) was beneficial for and desorption. The highest desorption ratio reached 7.58% for and 2.18% for . The desorption of was endothermic, whereas that of was exothermic. The desorption amounts of and decreased and increased, respectively, with the increase in desorption time. This study of the desorption characteristics of and in sludge-based biochar provides a theoretical basis for the subsequent utilisation of sludge-based biochar.

Removal of Zinc from Wastewater through the Reduction Potential Determination and Electrodeposition Using Adsorption-Desorption Solutions

The rubber product manufacturing industry generates large volumes of wastewater containing on average 10 ppm of zinc. Presently, zinc is removed via a chemical precipitation process generating hazardous precipitate that requires secure disposal. This study evaluated the removal of zinc through adsorption on Palm Shell Activated Carbon (PSAC) and subsequent desorption in hydrochloric, nitric (0.1 and 0.2 M), and citric (0.2 and 0.5 M) acids to produce solutions for the electrodeposition of zinc to achieve the permissible discharge level of 2 ppm. The highest desorption efficiency was achieved using HCl. Cyclic Voltammetry (CV) was applied to determine the reduction potential of zinc in desorption solutions. The presence of KCL and a buffer solution improved the electrodeposition of zinc. The chloride-based solution showed the best electroreduction behavior of zinc with a well-defined reduction peak as compared to the nitrate and citrate-based solutions, with a wider reduction peak and no peak, respectively. The chloride-based solution, selected for theelectrodeposition experiments, showed 64 % reduction in zinc concentration within 10 min. The prolonged to 30 min electrodeposition resulted in only 7 % of further increment. Overall, the obtained results confirm the feasibility of zinc removal through the electrodeposition from the adsorption-desorption solution, which provides an effective alternative to the currently industrially used chemical precipitation method.

Removal of aqueous Cr(VI) by magnetic biochar derived from bagasse

We prepared a novel adsorbent functionalized by bagasse magnetic biochar (BMBC). To study the removal behaviors and mechanisms of Cr(VI) by BMBC, batch adsorption experiments were conducted by modifying variables, such as pH, adsorption time, BMBC dosages, initial Cr concentration, co-existing ions, and ionic strength, and characterizing BMBC before and after Cr(VI) adsorption. BMBC was primarily composed of Fe2O3 and Fe3O4 on bagasse boichar with an amorphous structure. The specific surface area of BMBC was 81.94 m2 g−1, and the pHpzc of BMBC was 6.2. The fabricated BMBC showed high adsorption performance of Cr(VI) in aqueous solution. The maximum Cr(VI) adsorption capacity of BMBC was 29.08 mg g−1 at 25 ºC, which was much higher than that of conventional biochar sorbents. The adsorption process followed pseudo-second-order kinetics and could be explained by the involvement of the Langmuir isotherm in monolayer adsorption. The crystalline structure of Fe3O4 in the BMBC changed slightly during the adsorption process; Fe3O4 improved the adsorption of Cr(VI) on BMB. The desorption capacity of Cr(VI) was 8.21 mg g−1 when 0.2 mol L−1 NaOH was used as the desorption solution. After being reused three times, the removal efficiency is still as high as 80.36%.

Microfluidic-enabled versatile hyphenation of electromembrane extraction and thin film solid phase microextraction

In the present study, a versatile combination of electromembrane extraction (EME) with thin film solid phase microextraction (TF-SPME) was introduced using a microfluidic chip device. The device consisted of two single channels on two separate layers. The upper channel was dedicated to donor phase flow pass, while the beneath channel was used as a reservoir for stagnant acceptor solution. A slide of fluorine doped tin oxide (FTO) was accommodated in the bottom of the acceptor phase channel. A thin layer of polyaniline was electrodeposited on the FTO surface to achieve the required thin film for TF-SPME. A stainless-steel wire was embedded in the donor phase channel and another wire was also attached to the FTO surface. The channels were separated by a piece of polypropylene membrane impregnated with 1-octanol and the whole chip was fixed with bolts and nuts. The driving force for the extraction was an 8 V direct current (DC) voltage applied across the supported liquid membrane (SLM). Under the influence of the electrical field, analytes immigrated from sample towards the acceptor phase and then adsorbed on the thin film of the solid phase. Finally, the analytes were desorbed by successive movement of a desorption solvent in the acceptor phase channel followed by injection of the desorption solution to HPLC-UV. The applicability of the proposed device was demonstrated by the determination of four synthetic food dyes: Amaranth, Ponceau 4R, Allura Red, and Carmoisine, as the model analytes. The effective parameters on the efficiency of the both EME and TF-SPME were investigated. Under the optimized conditions, the microchip provided low LODs (1–10 μg L−1), and a wide linear dynamic range of 10–1000 μg L−1 for all analytes. The system also offered RSD values lower than 5.5% and acceptable reusability of the thin film for multiple extractions.

Development of tannin-immobilized cellulose fiber extracted from coconut husk and the application as a biosorbent to remove heavy metal ions

Cellulose fibers from coconut husk (CH) were modified with tannin and applied as a biosorbent for the removal of heavy metal ions including Cu(II), Cd(II), and Pb(II) in wastewater. To improve the ion adsorption efficiency of the cellulose fiber from CH, epichlorohydrin was used as a crosslinking agent to graft tannin molecules onto cellulose to produce tannin-immobilized cellulose fiber (TCF). Under an optimum condition at pH 5.0 and 30 min of contact time, the adsorption capacity was 38.02 mg/g, 59.52 mg/g, and 72.99 mg/g for Pb(II), Cd(II), and Cu(II) ions, respectively. Adsorption behaviors of the metal ions could be described using the Langmuir isotherm model. The desorbing solution containing 0.1 M EDTA was chosen to regenerate used TCF. Moreover, chemical characterizations of the TCF using Fourier transform infrared spectrometry showed that TCF possessed combined properties of both CH and tannin. The developed TCF is an inexpensive and efficient alternative that could be further developed as a platform for wastewater management.