Desorption Of Organic Compounds Research Articles

Micropollutants Removal from Water and Activated Carbon Regeneration by Combining Adsorption and Electro-Fenton

The presence of micropollutants in municipal wastewater effluents is a topic of major concern, as these pollutants end up in surface and ground waters. Currently, adsorption on activated carbon (AC) is used to remove these recalcitrant compounds. When saturated, the AC is generally either thermally regenerated or disposed of. Thermal regeneration is expensive and negatively affects the structure and adsorptive properties of the AC.Over the last decade, considerable attention has been directed towards the electrochemical advanced oxidation processes (eAOPs), due to their ability to remove a large range of organic pollutants from water even at very low concentrations [1]. eAOPs rely on the in-situ generation of powerful oxidants, such as HO• by electron transfer at the anode surface. However, these processes are limited by mass transfer and require high energy consumption.In this study, combined adsorption on granular activated carbon (GAC) and electro Fenton process (EF) is applied. The purpose of this coupled process is to overcome the mass transfer issue by pre-concentrating the compounds on AC and proposing a new AC regeneration method. During the EF the AC can directly be used as a cathode. Due to the electrostatic repulsions and oxidation process, the compounds are desorbed from the AC and oxidized by the HO• generated in the bulk. Material and Methods The adsorption cycles and EF experiments were performed in batch mode using deionized water (DW) and simulated wastewater (SWW) with caffeine as a model compound. Similar experimental steps and conditions as described in [2] are followed, using 1g of GAC, with pH=3, Fe2+= 0.15 mM, Na2SO4= 50mM, and a current intensity of 200 mA. To assess the degradation and mineralization of the caffeine, HPLC and TOC measurements were used, respectively. The regeneration efficiency was calculated by comparing the adsorption capacity of the AC after each regeneration cycle with its initial adsorption capacity. Results and Conclusions The efficiency of the process was discussed as regards (i) desorption of organic compounds and regeneration efficiency in DW and SWW, (ii) degradation and mineralization of organic compounds, and (iii) stability of GAC for several successive regeneration cycles. During the regeneration, over 80% of desorbed caffeine was degraded and 75% was mineralized due to the formed HO• by Fenton reaction and at the BDD anode surface (Fig.1). Furthermore, a recovery of the AC adsorption capacity by up to 50 % in PW and 37% in SWW was observed. These regeneration percentages decreased to 25% during the second cycle and then remained stable during the third and the fourth cycle. The incomplete regeneration is most likely due to remaining caffeine molecules at the AC [3], or a blockage of the carbon adsorption sites by formed degradation molecules. Hence, a longer treatment time might lead to higher efficiency. These hypotheses will be taken into consideration in future work to draw a clear conclusion on the regeneration phenomenon. The similar regeneration efficiencies and mineralization rates obtained during the 2nd,3rd, and 4th cycles indicate the stability of the GAC electrode.In conclusion, the results from this study illustrate that combined adsorption and EF is a suitable process for the removal of caffeine and regeneration of AC. The advantage of such a process is that part of the AC can be regenerated while over 75% of the desorbed compounds from the AC are mineralized, thus avoiding toxic effluents. This process is currently implemented as a continuous e-cell for sequential adsorption and EF regeneration.

Microbial degradation of nondesorbable organic compounds on biochars by extracellular reactive oxygen species

Knowledge of microbial degradation of biochar-adsorbed organic pollutants is essential for recovering adsorption performance of biochars and reducing secondary pollution in soil remediation. In previous study, desorption of organic compounds from biochars was perceived as a prerequisite for the microbial degradation. However, microbial degradation of the nondesorbable organic compounds on biochars has not been studied. Therefore, degradation of nondesorbable naphthalene (NAPH), phenanthrene (PHEN) and pyrene (PYR) on a wood chip-derived biochar (WBC700) by Sphingobium yanoikuyae B1 was investigated. Significant microbial degradations of nondesorbable organic compounds were observed and followed the order of NAPH < PHEN < PYR. It was newly observed in this study that the microbial degradation of nondesorbable organic compounds on WBC700 was mainly attributed to the •OH in extracellular fluid of Sphingobium yanoikuyae B1. The extracellular •OH was produced through a Fenton-like reaction involved siderophore, H2O2 and iron ions, which could be significantly enhanced by WBC700. Microbial degradation was higher for larger organic compound (e.g., PYR), because larger molecules were adsorbed in relatively larger micropores of WBC700 and thus could be accessible to more extracellular •OH for degradation. The obtained results could provide a new insight into the microbial degradation of biochar-adsorbed organic pollutants in soil remediation.

Electro-Fenton Regeneration of Activated Carbon Fibers for the Removal of Pharmaceutical Residues

Introduction The electro-Fenton process is based on in-situ production of the Fenton’s reagent in order to continuously generate hydroxyl radicals in the bulk solution [1]. It is also possible to promote the generation of additional powerful oxidant species by using anode material with high oxygen evolution overpotential. Therefore, such electrochemical advanced oxidation process (EAOP) is able to degrade a large range of organic pollutants [1]. However, energy efficiency of EAOPs is strongly affected by mass transport limitations during the treatment of low concentrations of pollutants such as pharmaceutical residues. In fact, a large amount of hydroxyl radicals are wasted in parasitic reactions such as hydroxyl radical dimerization. The combination of adsorption and electro-Fenton processes aims at overcoming this drawback. Adsorption on activated carbon fibers (ACFs) is used for pre-concentration of organic pollutants. Then, ACFs can be directly used as cathode during the electro-Fenton process for desorption, degradation and mineralization of organic compounds as well as for regeneration of ACFs for additional adsorption steps [2]. The possibility to easily regenerate ACFs improve the cost-effectiveness of this material, which presents more suitable characterisitcs than grain or powder activated carbon (e.g. low intra-particle diffusion limitation leading to fast adsorption kinetics, narrow pore size distribution leading to selective adsorption of micropollutants). This innovative strategy was applied for the removal of pharmaceutical residues. Scale-up from batch to continuous filtration reactor was investigated. Material and methods A first set of experiments was performed in batch reactor for both adsorption and electro-Fenton processes, by using clofibric acid and ofloxacin as model pharmaceutical residues. Design parameters (e.g. anode material: boron-doped diamond (BDD) or TiOx) and operational parameters (current density, treatment time) were optimized for improving regeneration efficiency and mineralization of pharmaceutical residues. Regeneration efficiency was assessed by comparing the adsorption capacity of regenerated ACFs and pristine ACFs. Mineralization rate of desorbed organic compounds was measured by total organic carbon analysis. Biodegradability and acute toxicity (Microtox®) of the solution was also assessed. ACFs were characterized by scanning electron microscopy, Hg porosimetry, and Raman spectroscopy. Then, the study was focused on the design, implementation and optimization of this combined process in a single continuous filtration reactor and using a real effluent. Results and discussion Batch experiments using clofibric acid as model pollutant were performed in order to better understand the influence of critical design and operational parameters. The efficiency of the process was discussed as regards to (i) desorption of organic compounds and regeneration efficiency, (ii) degradation and mineralization of organic compounds and (iii) stability of ACFs for several successive adsorption/regeneration cycles. By using BDD as anode and a current density of 21 mA cm-2, it was observed that increasing the treatment time from 3 to 6 h strongly improved the regeneration effectiveness from 45 to 75%. Further increasing the treatment time to 9 h did not show significant positive effect because of the lower availability of a portion of adsorbed compounds within the ACF porosity. Besides, dividing the current density by a factor of 2.5 (8 mA cm-2) only reduced the regeneration efficiency from 75 to 64%, indicating that low current density might be more cost-effective. Using TiOx instead of BDD anode also only reduced the regeneration efficiency from 64 to 60%. TiOx is a new promising electrode material that is much less expensive than BDD. Therefore, using TiOx anode was considered as a more cost-effective configuration. A great advantage of this process is also that >80% of organic compounds desorbed from ACF were mineralized, thus avoiding the production of a toxic effluent. Regeneration efficiency was then assessed during 10 cycles of adsorption/regeneration without significant decrease due to the protection of the ACF surface by the cathodic polarization effect. Finally, this treatment strategy was implemented in a continuous filtration reactor where both adsorption and electro-Fenton regeneration could take place sequentially. Process efficiency for treating a real effluent was assessed by comparing breakthrough curves of pristine and regenerated filters. The development of this technology is currently focused on point-of-use filters for domestic applications (about 5 liters per day) as well as on industrial wastewater treatment (pilot-scale unit able to treat 10-20 liters per hour).

Effect of condensing tetraethoxysilane on desorption of organic compound from porous polymer

The present article reports the easy to use approach on the application of tetraethoxysilane (TEOS) for the enhancement of drug release from mesoporous acrylic resin, in which a water insoluble dru...

Surface Modification of Rock-Forming Minerals of Diamond-Bearing Kimberlites under Interaction with Wastewater and Electrochemically Treated Water

The structural and chemical surface transformation of basic kimberlite-forming minerals (calcite, olivine, serpentine) under the contact with natural and waste mineralized water and products of electrochemical treatment of the water are studied using X-ray photoelectronic spectroscopy, scanning electron microscopy and X-ray spectral micro-analysis, and atomic force microscopy. It is found that contact with kimberlite extract and recycling water induces chemical modification of calcite surface, which consists in adsorption of hydrocarbon impurities, and chlorine- and silica-bearing compounds, majority of which are removed during interaction with the product of electrochemical treatment of recycling water. The change in the structural and chemical surface properties of rock-forming silicates, aside from adsorption–desorption of organic compound, is also connected with the distortion of nano-size layer structure after leaching of Mg, Fe and Si, and with the carbonatization of the surface.

Validation of thermodesorption method for analysis of semi-volatile organic compounds adsorbed on wafer surface

To prevent the degradation of the device characteristics it is important to detect the organic contaminants adsorbed on the wafers. In this respect, a reliable qualitative and quantitative analytical method for analysis of semi-volatile organic compounds which can adsorb on wafer surfaces is of paramount importance. Here, we present a new analytical method based on Wafer Outgassing System (WOS) coupled to Automated Thermal Desorber-Gas chromatography-Mass spectrometry (ATD-GC-MS) to identify and quantify volatile and semi-volatile organic compounds from 6", 8" and 12" wafers. WOS technique allows the desorption of organic compounds from one side of the wafers. This method was tested on three important airborne contaminants in cleanroom i.e. tris-(2-chloroethyl) phosphate (TCEP), tris-(2-chloroisopropyl) phosphate (TCPP) and diethyl phthalate (DEP). In addition, we validated this method for the analysis and quantification of DEP, TCEP and TCPP and we estimated the backside organic contamination which may contribute to the front side of the contaminated wafers. We are demonstrating that WOS/ATD-GC-MS is a suitable and highly efficient technique for desorption and quantitative analysis of organophosphorous compounds and phthalate ester which could be found on the wafer surface.

Influence of Functional Groups on Desorption of Organic Compounds from Carbon Nanotubes into Water: Insight into Desorption Hysteresis

Adsorption-desorption of nitrobenzenes, phenols, and anilines on five multiwalled carbon nanotubes (MWCNTs) with different degrees of surface oxidation were investigated to examine the influence of functional groups of both organic chemicals and CNTs on desorption hysteresis. Desorption hysteresis was not observed for nitrobenzenes, phenols, and 4-nitroaniline from all MWCNTs. Significant desorption hysteresis was observed for aniline and 4-methylaniline on surface-oxidized MWCNTs but not on unoxidized MWCNTs. Formation of an irreversible amide bond (i.e.,-CONH-) by amidation reaction of amino group of anilines with oxygen-containing groups (i.e., carboxyl or lactonic groups) on MWCNTs was observed. We proposed that desorption hysteresis could be attributed to the immobilization of organic compounds on the surface of CNTs resulting from the irreversible chemical reaction/binding. The irreversible chemical immobilization is compound functional group selective and dependent on the surface oxygen-containing groups of CNTs. Hysteresis index (HI) values of aniline or 4-methylaniline on MWCNTs increased with the amounts of oxygen-containing groups on MWCNTs. Moreover, HI values of anilines on a given oxidized MWCNT followed an order of 4-nitroaniline < 4-chloroaniline < aniline < 4-methylaniline.

Design of a low‐temperature plasma (LTP) probe with adjustable output temperature and variable beam diameter for the direct detection of organic molecules

The direct detection of organic molecules by mass spectrometry requires ionization methods which are compatible with ambient conditions. A relatively new strategy is the use of a free low-temperature plasma beam for ionization. The objective is to design a safe and adjustable plasma beam to enable optimal ionization and desorption parameters for specific molecules. A plasma probe based on a dielectric barrier discharge was designed, where the plasma is guided through an internal second tube. This setup permits different beam diameter settings and the control of the plasma temperature. The ionization and desorption of pure organic compounds, as well as their direct detection from roasted coffee beans, were tested. The presented plasma probe provides improved safety with respect to arcing, ozone generation and electric shock, compared with conventional designs. The functionality of previously reported devices is expanded. A defined plasma diameter can be set by choosing the appropriate insert, while the input voltage controls the plasma temperature. The variation of measurement parameters enables the optimized direct detection of target compounds from roasted coffee beans, such as caffeine, guaiacol and vanillin. The presented low-temperature plasma probe allows the fine-tuning of ionization and desorption parameters, according to the target molecules. Possible applications include: (1) The ambient ionization and desorption of organic compounds with different volatility and (2) The direct analysis of food products such as roasted coffee beans.

Physisorption and Desorption of Diethyl Phthalate and Isopropanol on a Silicon Surface

Physisorption and desorption of organic compounds on a silicon surface in a two-component system consisting of isopropanol (IPA) and diethyl phthalate (DEP) were measured in situ by means of a quartz crystal microbalance and were analyzed based on the rate theory. The surface concentration in a steady state changed corresponding to the gas-phase concentrations of IPA and DEP. The measured surface concentration in a steady state was reproduced by calculation taking into account the larger limit of surface concentration which depended on the rate parameters of the organic compounds. The area occupied by the organic molecules, estimated in this study, indicated that the interaction between DEP molecules and IPA molecules on silicon surface was quite small in a two-component IPA-DEP system.

Removal of Harmful Organic Compounds in Water Using Temperature-Sensitive Polymer Gel

The removal of harmful organic materials in water has been carried out using the adsorption and desorption characteristics of a temperature-sensitive polymer gel which is synthesized from polyvinylalcohol (PVA). Two types of polymerization degrees (1700 and 2500) of PVA were used in this experiment. The gel volume in water was induced at around 310 K for 1700 and 320 K for 2500. At higher temperatures, the temperature sensitive polymer gel shrinks because of discharging water, whereas, in contrast, at lower temperatures, the gel swells as a result of absorbing water. The reversibility of the volume change of the synthesized polymer gel is confirmed by changing temperature. The adsorption behavior of organic compounds onto PVA polymer gels in water was investigated at various temperatures. The amount of adsorption of organic compounds increases remarkably at temperatures higher than about 310 K for 1700 and 320 K for 2500. The organic compound in water could be adsorbed and desorbed reversibly onto PVA polymer gel by the temperature swing. The mechanism of adsorption and desorption of organic compounds onto gel can be explained by the hydration and dehydration of the polymer gel. The driving force of the adsorption is thought to be the hydrophobic interaction between PVA polymer gel and organic compounds.

Sorption properties of macroporous and hypercrosslinked copolymers

The sorption of organic compounds by porous copolymers of different porous structure and polarity was investigated with laboratory and commercial samples. The sorption capacity of hypercrosslinked copolymers is up to three times higher than that of macroporous samples. The described hypercrosslinked polymeric adsorbents are able to trap large quantities of adsorbates repeatedly. The kinetics of both adsorption and desorption of organic compounds from water is very fast for all adsorbents under investigation.

Chamber testing of adsorption of volatile organic compounds (VOCs) on material surfaces.

A simple test chamber method to quantify adsorption and desorption of organic compounds on material surfaces is described. Important environmental parameters such as temperature, relative humidity and air velocity were varied and controlled independently around typical indoor values. Experiments were performed with alpha-pinene and toluene in concentrations of 160-300 micrograms/m3. The measurements show adsorption on and desorption from wool carpet, nylon carpet, polyvinyl chloride (PVC) floor coverings, cotton curtain material and the empty chamber. The ranking of the materials, with respect to their sorption capacity, is as mentioned above. The adsorption of alpha-pinene was higher than the adsorption of toluene for all the materials. Air velocity was not found to influence the sorption of alpha-pinene and toluene on wool carpet, tested with air velocities at 0, 10 and 20 cm/s. The experiments were carried out during both the adsorption and the desorption phase. The uncertainty of the experiments was lowest during the desorption phase. Based on the results obtained, it can be recommended that sorption experiments should be performed as desorption phase experiments. A one-sink model, based on the Langmuir adsorption isotherm, appears adequate to describe the results.

Assessment of occupational exposure to diesel fumes--parameter optimization of the thermal coulometric measurement method for carbon.

'Elemental' carbon (EC) is used as a surrogate to assess occupational exposure to diesel soot. EC thermal analysis needs complete desorption of organic compounds from the soot particles prior to analysis in order to minimize positive interferences and artefacts. The desorption of the organic compounds can be considered as the major step which influences the reliability of the EC determination. A systematic study was carried out to investigate the different parameters of influence such as desorption temperature, desorption duration, heating rate and type of the sample on the desorption efficiency. It was found that temperature and duration are the major parameters of influence on the desorption efficiency. The influence of the sample load can be seen as a measure of the pyrolysis susceptibility of the sample. An optimized temperature program is proposed.

A stable mercury film on gold through conducting polypyrrole layer for electrochemical quartz crystal microbalance

Recently, electrochemical quartz crystal microbalance with gold electrode has been used extensively to elucidate the detailed mechanism during the electrochemical reaction through mass changes. Because of the formation of mercury amalgam, a large frequency fluctuation prevents this technique with mercury on gold from its application to measure mass changes due to adsorption or/and desorption of organic compounds. Electrochemical study of MR19 and MR19-Tb 3+ ion was successfully demonstrated at Hg film on gold and Hg film on polypyrrole layer which was formed on gold by potentiostatic method.

Sorption and desorption of organic compounds by synthetic polymeric sorbents

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSorption and desorption of organic compounds by synthetic polymeric sorbentsJiri Hradil, Frantisek Svec, V. V. Podlesnyuk, R. M. Marutovskii, L. E. Fridman, and N. A. KlimenkoCite this: Ind. Eng. Chem. Res. 1991, 30, 8, 1926–1931Publication Date (Print):August 1, 1991Publication History Published online1 May 2002Published inissue 1 August 1991https://doi.org/10.1021/ie00056a039RIGHTS & PERMISSIONSArticle Views119Altmetric-Citations20LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (700 KB) Get e-Alerts Get e-Alerts

On the desorption of electrosprayed organic compounds from supporting metal foils by laser induced pressure waves

The desorption of organic compounds by indirect effects of laser impact, as pressure waves, was examined in a transmission type laser microprobe mass analyzer. For this, the samples were electrosprayed on one side of a supporting metal foil a few microns thick. The sample layer was directed towards the mass analyzer and the uncovered side of the foil was exposed to the laser pulse. The metal foil served to absorb the laser energy, to transfer it to the sample layer and, at the same time, to shield the mass analyzer against the ions generated by direct laser-sample interaction. Mass spectra of the ions produced on the sample-layer side were registered and, afterwards, both sides of the foil were examined in a scanning electron microscope. At laser irradiances exceeding 5 × 10 8W cm −2, but not enough to perforate the foil, the electrosprayed material was, independent of the type of compound, split off from a circular region comparable to the spot size of the direct interaction zone. From compounds which are known to be desorbed directly as preformed ions, the spectra showed only the molecular cation peak. However, from compounds like oligosaccharides, which normally require cationization with alkali ions, neither quasi-molecular nor fragment ions were detected.

The Reversibilities of the Adsorption and Desorption of Organic Compounds in Water

Abstract The reversibilities of the adsorption and desorption of seventeen organic compounds in water on a granular activated carbon and a polystyrene adsorbent were examined by means of a batch-adsorption method. The adsorptions of many organic compounds were reversible, but the adsorptions of several phenolic compounds and aniline were irreversible for the activated carbon, because these compounds were adsorbed strongly on the surface of activated carbon by the π-electron combination. On the other hand, the adsorptions of all the organic compounds were reversiible for the polystyrene adsorbent.