Chloroxylenol Research Articles

Synthesis and Antibacterial Activity of PCMX Derivative

Abstract: Para Chloro Meta Xylenol (PCMX) is an exceptionally broad spectrum bactericide and preservative with a long established and proven use in controlling bacteria, mildew and fungal growth in a wide range of applications (medical, domestic and industrial). Chloroxylenol, also known as para chloro meta xylenol, is an antiseptic and disinfectant which is used for skin disinfection and cleaning surgical instruments. It is also used within a number of household disinfectants and wound cleaners. Their analogues viz. hybrid / ester molecules also possess various biological activities which prompted us to synthesize a novel analogue for their future application as bioactive molecule. The synthesized compound was characterized by IR, 1HNMR, mass spectral data, elemental analysis and screened for its potential antibacterial activity against Gram positive and Gram negative bacteria. It shows a promising antibacterial activity.

Long-term influence of chloroxylenol on anaerobic microbial community: Performance, microbial interaction, and antibiotic resistance gene behaviors

The use of antibacterial and disinfection products is increasing in recent years. Para-chloro-meta-xylenol (PCMX), a widely used antimicrobial agent, has been detected in various environments. Herein, the impacts of PCMX with long-term exposure on anaerobic sequencing batch reactors were investigated. The high concentration (50 mg/L, GH group) PCMX severely inhibited the nutrient removal process, and the low concentration group (0.5 mg/L, GL group) slightly affected the removal efficiency which was recovered after 120 days of adaptation compared to the control group (0 mg/L, GC group). Cell viability tests indicated that PCMX inactivated the microbes. A significant reduction in bacterial α-diversity was observed in the GH but not the GL group. The microbial communities were shifted upon PCMX exposure, among which Olsenella, Novosphingobium, and Saccharibacteria genera incertae Sedis became the predominant genera in the GH groups. Network analyses showed that PCMX significantly reduced the complexity and interactions of the microbial communities, consistent with the negative impacts on bioreactor performance. Real-time PCR analysis indicated that PCMX affected the behavior of antibiotic resistance genes (ARGs), and the relationship between ARGs and bacterial genera gradually became complicated after long-term exposure. Most detected ARGs decreased on Day 60 but increased on Day 120 especially in the GL group, implying the potential risk of environment-relevant concentration of PCMX in the ecosystems. This study provides new insights into the understanding of the impacts and risks of PCMX on wastewater treatment processes.

Phenotypic ESBL and non-phenotypic ESBL isolates of Klebsiella pneumoniae exhibit differing responses to induced antimicrobials resistance and subsequent antibiotic cross-resistance.

To investigate the effect of adapting Klebsiella pneumoniae clinical isolates harboring ESBL genes to cetrimide (CT) in terms of subsequent cross-resistance to other biocides and antibiotics, and to investigate changes to virulence markers, such as biofilm formation and efflux activity. The changes between phenotypic extended spectrum β-lactamases (pESBL) expressing isolates and non-phenotypic ESBL (npESBL) isolates was compared. Kl. pneumoniae isolates (14 pESBL and 17 npESBL) were adapted to increasing concentrations of CT, until 4 × MIC was reached. The MIC of the adapted isolates was tested against chloroxylenol (CX) and chlorhexidine. Disk diffusion techniques were used to determine the susceptibility of the isolates to different antibiotics. Biofilm formation was assessed for the isolates using the crystal violet method and efflux pump activity was studied using the ethidium bromide assay. After CT adaptation, 100% of npESBL isolates and 85.7% of pESBL isolates showed increase in CT MIC after CT adaptation. While 41.2% of npESBL and 57.1% of the pESBL isolates showed a cross-resistance with chlorhexidine. CT adaptation resulted in a significant decrease in the susceptibility of npESBL isolates to aztreonam and cefotaxime compared to pESBL isolates, which could be linked to the increase in efflux activity of npESBL compared to pESBL. Biofilm formation was significantly increased after CT adaptation regardless of the type of isolate. The extensive use of biocides in the environment can induce cross-resistance to other biocides and antibiotics, and can increase the ability of bacteria to form biofilms. The response of bacteria to biocide adaptation differs between pESBL and npESBL isolates, although the effect is strain specific.

Occurrence and stability of PCMX in water environments and its removal by municipal wastewater treatment processes

Para-chloro-meta-xylenol (PCMX) is a synthetic antiseptic used extensively to control the spread of germs and viruses, and as a result, enormous amount of PCMX could be discharged to water environments through drainage. To investigate the extent of PCMX contamination, water samples were collected from rivers and coastal waters in Hong Kong, and PCMX concentrations were determined by a newly developed method using liquid chromatography-tandem mass spectrometry combined with stable isotope-dilution. We discovered widespread PCMX pollution in the water environment. Then, we revealed for the first time that PCMX in wastewater is not effectively removed by chemically enhanced primary treatment (CEPT), one of the wastewater treatment processes used in Hong Kong (∼75% of wastewater) and other megacities around the world. This suggests that the CEPT effluent or the primary treatment effluent is an unintended continuous source of pollution for PCMX in water environments. Finally, we found that PCMX was relatively stable in the water environment and could pose a risk to aquatic organisms. These findings underscore the importance of raising public awareness of the environmental consequences from overuse of PCMX-based disinfectants and the need to reevaluate the various wastewater treatment processes in removing PCMX.

Impact of benzalkonium chloride, benzethonium chloride and chloroxylenol on bacterial antimicrobial resistance.

This review examined 3655 articles on benzalkonium chloride (BKC), benzethonium chloride (BZT) and chloroxylenol (CHO) aiming to understand their impact on antimicrobial resistance. Following the application of inclusion/exclusion criteria, only 230 articles were retained for analysis; 212 concerned BKC, with only 18 for CHO and BZT. Seventy-eight percent of studies used MIC to measure BKC efficacy. Very few studies defined the term 'resistance' and 85% of studies defined 'resistance' as <10-fold increase (40% as low as 2-fold) in MIC. Only a few in vitro studies reported on formulated products and when they did, products performed better. In vitro studies looking at the impact of BKC exposure on bacterial resistance used either a stepwise training protocol or exposure to constant BKC concentrations. In these, BKC exposure resulted in elevated MIC or/and MBC, often associated with efflux, and at time, a change in antibiotic susceptibility profile. The clinical relevance of these findings was, however, neither reported nor addressed. Of note, several studies reported that bacterial strains with an elevated MIC or MBC remained susceptible to the in-use BKC concentration. BKC exposure was shown to reduce bacterial diversity in complex microbial microcosms, although the clinical significance of such a change has not been established. The impact of BKC exposure on the dissemination of resistant genes (notably efflux) remains speculative, although it manifests that clinical, veterinary and food isolates with elevated BKC MIC carried multiple efflux pump genes. The correlation between BKC usage and gene carriage, maintenance and dissemination has also not been established. The lack of clinical interpretation and significance in these studies does not allow to establish with certainty the role of BKC on AMR in practice. The limited literature and BZT and CHO do not allow to conclude that these will impact negatively on emerging bacterial resistance in practice.

Influence of anode material and chlorides in the new-gen solid polymer electrolyte cell for electrochemical oxidation – Optimization of Chloroxylenol degradation with response surface methodology

• Efficient removal of Chloroxylenol with BDD/SPE in low conductive solutions. • First application of Ti/RuO 2 (DSA) as anode coupled with solid polymer electrolyte. • Application of response surface methodology for process optimization. • Optimization allows decreasing the energy consumption preserving COD removal. • Promising results for DSA/SPE application in chlorinated environments. In this study the solid polymer electrolyte – based (SPE-based) system recently developed for electrochemical wastewater treatment is used for the degradation of Chloroxylenol (CXL). To the best of authors knowledge, this is the first study that deals the investigation of the effect of anode material in such electrochemical cell configuration. The most used BDD/SPE cell is compared with DSA/SPE (Ti/RuO 2 anode) system considering the effect of chlorides concentration to activate the process mediated by active chlorine. The preliminary tests to evaluate the feasibility of the process show that BDD/SPE is able to completely degrade the CXL reaching a COD removal close to 90 % also in absence of supporting electrolyte and in a low conductive solution (0.025 mS cm −1 ). The DSA anode suffers the lack of chlorides in solution but became more competitive when NaCl is added, with a maximum COD removal equal to 71.6 % with 50 mM NaCl. The response surface methodology based on three-factors Doehlert matrix is applied to optimize the operating conditions for both systems. The selected factors are the current density (2–20 mA cm −2 ), the NaCl concentration (0–20 mM), and CXL concentration (10–100 mg L −1 ). The optimization analysis allows identifying the operating conditions needed to maximize COD removal and to minimize energy consumptions for BDD/SPE and DSA/SPE setups. In particular, the RSM analysis shows that under peculiar conditions (i = 15.5 mA cm −2 ; NaCl > 13 mM) DSA/SPE can reach a COD removal analogous to those obtained with BDD electrode over 90%, suggesting the possibility to exploit this electrode material in solid polymer electrolyte electrochemical cells.

Antimicrobial PCMX facilitates the volatile fatty acids production during sludge anaerobic fermentation: Insights of the interactive principles, microbial metabolic profiles and adaptation mechanisms

Para-chloro-meta-xylenol (PCMX), as a massively used antimicrobial agent, exhibited dose-dependent effects on the sludge fermentation for volatile fatty acids (VFAs). The presence of PMCX at environmental levels (10–20 mg/g TSS) promoted the VFAs production by 2.5–3.0 folds but caused evident inhibition at high level (100 mg/g TSS). PCMX synchronously promoted the sludge solubilization, hydrolysis, and acidification but inhibited methanogenesis. Mechanistic investigations revealed that PCMX could interact with the extracellular polymeric substances (EPS) in sludge and cause the release of biodegradable substrates (especially proteins) by altering the WAS structures. Moreover, the functional fermentative bacteria (i.e., Firmicutes and Chloroflexi) were enriched while those VFAs consumers (i.e., Methanothrix and Methanomassiliicoccus) were reduced with low level of PCMX exposure. The microbial enzymatic activities (i.e., protease) and critical genes relevant to the substrates transport (i.e., gluC and lhpN) and metabolisms (especially the proteins, i.e., pckA), and VFAs biosynthesis (i.e., fabG) were all upregulated with the low PCMX stimulus. The microbial response and adaptation to PCMX toxicity were mainly attributed to the regulation of two-component and quorum sensing systems. Overall, PCMX contributed to the VFAs accumulation during sludge fermentation by mainly interacting and disrupting the sludge structures, and improving the microbial metabolic function traits. This work provided new insights into exogenous pollutants’ interactions, potential influences, and reaction mechanisms in the complicated sludge matrix.

Study on Synthesis of Fungicide Para–Chloro–Meta-Xylenol

Study on Synthesis of Fungicide Para–Chloro–Meta-Xylenol

Fabrication of thermoresponsive metal-organic nanotube sponge and its application on the adsorption of endocrine-disrupting compounds and pharmaceuticals/personal care products: Experiment and molecular simulation study.

Thermoresponsive metal-organic nanotube modified (MONT-pNIPAM, pNIPAM=poly N-isopropylacrylamide) sponge was synthesized using the dip-coating method and served as an adsorbent for endocrine-disrupting compounds (EDCs) and pharmaceuticals/personal care products (PPCPs) removal. The material was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and N2 sorption-desorption. Nonlinear regression-based equations were derived to optimize pH and ionic strength during process. Though thermoresponsive polymer phase transition between dissolve and aggregate, realizing the adsorption tunnel "ON-OFF" under the temperature control. Adsorption kinetics and isotherms were investigated on the basis of a static experiment. The pseudo-second-order kinetic model and the Langmuir isotherm were fitted well to characterize adsorption. At an initial concentration of 50mgL-1, maximum adsorption capacity were 128mg/g, 184mg/g and partition coefficient were 1.09mgg-1 μM-1, 1.13mgg-1 μM-1 for dibutyl phthalate (DBP) and parachlorometaxylenol (PCMX), respectively. The density-functional theory (DFT) was applied to calculate the interaction energy and investigate the possible mechanism. Combining the experimental data with theoretical calculation, results demonstrated that the MONT-pNIPAM sponge was a highly efficient adsorbent material that was suitable for the removal of EDCs/PPCPs from water.

Carbon-derived from metal-organic framework MOF-74: A remarkable adsorbent to remove a wide range of contaminants of emerging concern from water

Five typical Zn-based metal-organic frameworks (MOFs) such as MOF-74(Zn) were pyrolyzed to obtain carbons-derived from MOFs (CDMs). The carbon-derived from MOF-74(Zn) or CDM-74 was firstly applied, together with other four CDMs and commercial activated carbon (AC), in the adsorptive removal of five representative contaminants of emerging concern (CECs) such as phthalic acid, diethyl phthalate, N,N-diethyl-3-methylbenzamide (DEET), chloroxylenol (CLXN) and oxybenzone (OXB) from water. CDM-74, with high mesopore volume and acid sites density, showed the highest capacity for the adsorption of DEET, OXB and CLXN from water among the tested and any reported adsorbent, so far. The plausible adsorption mechanism could be suggested, or H-bonding was important in the adsorption where the DEET and CDM-74 (especially phenolics) can be H-acceptor and H-donor, respectively. Based on the highest adsorption capacity for three adsorbates and facile recyclability, CDM-74 could be suggested as a potential adsorbent to eliminate a wide range of CECs from water.

Porous Aromatic Framework Modified Electrospun Fiber Membrane as a Highly Efficient and Reusable Adsorbent for Pharmaceuticals and Personal Care Products Removal.

Water contamination by emerging organic pollutants, such as pharmaceuticals and personal care products (PPCPs), is becoming more and more serious. Porous aromatic frameworks (PAFs) are considered as promising adsorbents to remove the PPCPs. To overcome the limitation of PAFs in their powder forms for large-scale applications, herein, we proposed a strategy to covalently anchor PAFs onto electrospun polymer fiber membranes. Polyaniline (PANI) played the role of aromatic seed layer, which was coated on the electrospun polyacrylonitrile (PAN) fiber membrane first. Then, PAF-45 modification was in situ synthesized in the presence of the PANI-coated electrospun PAN fiber membrane. This study could make the PAF-based materials be handled more easily and improve the surface area of electrospun fiber membrane. The obtained composite adsorbent (PAF-45-PP FM) was applied for the adsorption of three PPCPs: ibuprofen (IBPF), chloroxylenol (CLXN), and N, N-diethyl-meta-toluamide (DEET), which exhibited high adsorption capacity and good recycling ability. According to the Langmuir model, the maximum adsorption capacities of PAF-45-PP FM toward IBPF, CLXN and DEET were 613.50, 429.18, and 384.61 mg/g, respectively. In addition, after ten adsorption-desorption cycles, the adsorption capacities toward the three PPCPs decreased slightly. Through an adsorption comparison test, the adsorption capacity of PAF-45-PP FM almost attributed to the loading PAF-45. The adsorption mechanism analysis illustrated that there were pore capture, hydrophobic interaction and π-π interaction between PPCPs and PAF-45-PP FM. Therefore, the PAF-45-PP FM can be potential adsorbents to purify water contaminated with PPCPs.

Removal of Chloroxylenol Disinfectant by an Activated Sludge Microbial Community

Chloroxylenol (CHL) is an antimicrobial ingredient that is frequently used in antiseptics/disinfectants for skin (e.g. hand soap) and non-living surfaces. CHL is an alternative to triclosan and triclocarban, the use of which has recently been banned in some countries. Accordingly, the more widespread use of CHL may significantly increase its occurrence and level in aquatic environments in the near future, eventually resulting in potential ecological risks. Wastewater treatment plants (WWTPs) may be a point source of CHL in natural environments due to extensive discharge through urban waste stream disposal. While the satisfactory removal of CHL in WWTPs is critical for maintaining healthy aquatic ecosystems, the extent of CHL removal and whether CHL causes system upset/failure in WWTPs currently remain unknown. In the present study, we conducted bioreactor operation and batch experiments to investigate the fate and effects of CHL and elucidate the mechanisms underlying degradation at various levels from environmentally relevant to high levels (0.5–5 mg L−1). Bioreactors partially removed CHL (44–87%) via a largely biological route. Microbial association networks constructed using 16S rRNA gene sequencing data revealed selective enrichment and a correlation between Sphingobium and CHL, implying its involvement in the biological breakdown of CHL through dehalogenation and ring hydroxylation pathways. The present results provide insights into the behavior and effects of CHL in activated sludge communities and important information for the sustainable management of CHL that may be an emerging issue in the urban water cycle.

Effectiveness of surgical hand antisepsis using chlorhexidine digluconate and parachlorometaxylenol hand scrub: Cross-over trial.

Background:Chlorhexidine and parachlorometaxylenol (PCMX) are antiseptics recommended for surgical hand antisepsis. To our knowledge, PCMX has not been evaluated for bactericidal efficacy “in vivo.Methods:We conducted a randomized, double-blind, controlled crossover trial to compare the bacterial loads on fingertips and fingernails under laboratory conditions after use of antiseptic test products, including chlorhexidine digluconate 4%, PCMX 3%, and a reference solution of propan-1-ol 60% (P-1). We assessed bacterial load after a prewash with soft soap, immediately after application of an antiseptic, and 3 hours after application and wearing of sterile, powder-free gloves. Our procedures followed those specified by European Norm (EN) 12791 for evaluating surgical hand antiseptics and using cotton swab for fingertips and fingernails.Results:Chlorhexidine digluconate 4% and PCMX 3% did not decrease bacterial load on the hands. The bactericidal performances of chlorhexidine digluconate 4% and PCMX 3% did not differ significantly. Chlorhexidine digluconate 4% and PCMX 3% increased bacterial load on the fingertips after participants had worn gloves for 3 hours. Fingernails had greater bacterial loads than skin on the fingertips.Conclusions:Chlorhexidine digluconate 4% and PCMX 3% had similar bactericidal efficacy, but they failed to meet the EN 12791 efficacy standard. Fingernails should be a particular focus of antisepsis in preparation for surgery.The trial was registered at ClinicalTrials.gov (ID: NCT02500758).

Benzalkonium chloride, benzethonium chloride, and chloroxylenol - Three replacement antimicrobials are more toxic than triclosan and triclocarban in two model organisms.

With the recent ban of triclosan (TCS) and triclocarban (TCC) from some personal care products, many replacement antimicrobial compounds have been used. Yet the potential health risk and environmental impact of these replacement compounds are largely unknown. Here we investigated the toxicological effects of three commonly used replacement antimicrobials, benzalkonium chloride (BAC), benzethonium chloride (BEC), and chloroxylenol (CX) to two model organisms, the nematode C.elegans and zebrafish (Danio rerio), and compared them to the banned TCS and TCC. We found that these replacement compounds are not any safer than the banned antimicrobials. In the worm, at least one of the three, BAC, showed comparable toxicity to TCS from organismal to molecular levels, with toxic effects occurring at lower hundred μg/L to lower mg/L levels. In the fish, all three compounds at the tested concentration ranges (0.05-5 mg/L) showed toxicity effects to zebrafish embryos, indicated by hatching delay or inhibition, embryonic mortality, morphological malformations, and neurotoxicity. BAC was the most toxic among the three, with acute lethal toxicity occurring at environmentally relevant concentrations (hundreds of μg/L), which is comparable to the banned TCC. However, the toxicity effects of BAC and TCC occurred within different time windows, potentially suggesting different mechanisms of toxicity. CX was the only compound that induced a "body curvature" phenotype among the five compounds examined, suggesting a unique mode of toxic action for this compound. Furthermore, all five compounds except TCS induced neurotoxicity in fish larvae, indicated by alterations in secondary motoneuron axonal projections. Such neurotoxicity has been largely understudied for these antimicrobials in the past years and calls for further investigations in terms of its underlying mechanisms and ecological significance. These findings strongly indicate that scrutiny should be put on these replacement compounds before their introduction into massive use in personal care products.

Nitrogen-doped porous carbon from ionic liquid@Al-metal-organic framework: A prominent adsorbent for purification of both aqueous and non-aqueous solutions

Nitrogen-doped porous carbons were derived through direct carbonization of ionic liquid (IL)-loaded Al-based metal-organic frameworks (MOFs, or porous coordination polymers) called AlPCP (IL@AlPCP), where IL was added to increase nitrogen contents of derived carbons. Porous carbons derived from IL@AlPCP and pristine AlPCP (called CDIL@AlPCP and CDAlPCP, respectively) were characterized using various techniques and utilized in liquid-phase adsorptions for both aqueous and non-aqueous media to realize their potential application in water and fuel purifications. The adsorptive performance of CDIL@AlPCP was remarkable for the removal of several pharmaceutical and personal care products from water. For example, the adsorption capacity of CDIL@AlPCP was thus far found to be the highest for para-chloro-meta-xylenol (PCMX) as compared with any reported adsorbent (including CDAlPCP and AC). Moreover, CDIL@AlPCP was also very effective for triclosan and acetaminophen adsorptions. Similarly, the efficiency of CDIL@AlPCP for adsorptive desulfurization and denitrogenation of the model fuel was also noticeable. The remarkable adsorption efficiency of CDIL@AlPCP for both aqueous and non-aqueous phases was explained in terms of mainly H-bonding. The direction of H-bonding can also be defined (for example, PCMX contributed as an H-donor, and ample N and O species of carbon materials contributed as an H-acceptor). Moreover, CDIL@AlPCP can be regenerated through simple ethanol washing and can be reused several times. Therefore, CDIL@AlPCP is recommended as a promising adsorbent for purification of both aqueous and non-aqueous solutions.

MRSA decolonization failure\u2014are biofilms the missing link?

BackgroundDevice-associated infections due to biofilm-producing methicillin-resistant Staphylococcus aureus (MRSA) have been recently associated with the failure of antibiotic treatment and decolonization measures. The goal of our study was to evaluate the extent to which the formation of biofilms influenced the efficacy of topical decolonization agents or disinfectants such as mupirocin (MUP), octenidine (OCT), chlorhexidine (CHG), polyhexanide (POL), and chloroxylenol (CLO).MethodsBacterial killing in biofilms by the disinfectants and MUP was determined as the reduction [%] in metabolic activity determined by a biofilm viability assay that uses kinetic analysis of metabolic activity. The test substances were diluted in water with standardized hardness (WSH) at 25 °C at the standard concentration as well as half the standard concentration to demonstrate the dilution effects in a practical setting. The tested concentrations were: CHG 1%, 2%; OCT 0.1%, 0.05%; PH 0.04%, 0.02%; and CLO 0.12%, 0.24%. A test organism suspension, 1 mL containing ~1 × 109 bacterial cells/mL, and 1 mL of sterile WSH were mixed and incubated for six different exposure times (15 s, 1, 3, 5, 10 and 20 min) after the test substance was added.Additionally, the bactericidal effects of all substances were tested on planktonic bacteria and measured as the log10 reduction.ResultsThe disinfectants OCT and CHG showed good efficacy in inhibiting MRSA in biofilms with reduction rates of 94 ± 1% and 91 ± 1%, respectively. POL, on the other hand, had a maximum efficacy of only 81 ± 7%. Compared to the tested disinfectants, MUP showed a significantly lower efficacy with <20% inhibition (p < .05). Bactericidal effects were the greatest for CHG (log10 reduction of 9.0), followed by OCT (7.7), POL (5.1), and CLO (6.8). MUP, however, showed a very low bactericidal effect of only 2.1. Even when the exposure time was increased to 24 h, 2% MUP did not show sufficient bactericidal effect.ConclusionsOur data provide evidence that OCT and CHG are effective components for disinfection of MRSA-biofilms. On the other hand, exposure to MUP at the standard concentrations in topical preparations did not effectively inhibit MRSA-biofilms and also did not show adequate bactericidal effects. Combining an MUP-based decolonization regimen with a disinfectant such as OCT or CHG could decrease decolonization failure.

Solvation of Parachloro Meta Xylenol (PCMX) in AlcoholsAqueous Solutions at 293.15 K

Solvation of Parachloro Meta Xylenol (PCMX) in AlcoholsAqueous Solutions at 293.15 K

Modelling the transient behaviour of a fixed bed considering both intra and inter-pellet diffusion for adsorption of parachloro-meta-xylenol (PCMX)

Abstract Phenols and Phenolics are considered to be potentially hazardous water pollutants. Parachlorometaxylenol (PCMX) is the major component of several disinfectants, produced commercially by well-known pharmaceutical companies. Adsorption of PCMX in various combinations of adsorbents, both natural and artificial, has been studied. Specially, water hyacinth (Eichhornia crassipes [Mart] Solms-Laubach) stems were used as adsorbent in combination with powdered activated carbon (PAC) and granular activated carbon (GAC). Five equilibrium isotherm models, namely, Tempkin Isotherm, Freundlich Isotherm, Langmuir Isotherm, Redlich-Peterson Isotherm and Toth Isotherm were studied and parameterized. The dynamics of fixed-bed adsorption columns for modeling is a demanding task due to the strong nonlinearities in the equilibrium isotherms, interference effects of the competition of solutes for adsorbent sites, mass transfer resistances between fluid phase and solid phase and fluid-dynamic dispersion phenomena. A mathematical model has been studied for a fixed bed isothermal adsorption column with porous adsorbent. Simulations were carried out to understand the specific influence of inter-pellet diffusion and external film resistance. The effect of flow rate, bed length and initial concentration of adsorbate were studied. Rapid occurrence of breakthrough time was observed for higher flow rates of effluent, lower bed height and high initial concentration of effluent.

Modelling the transient behaviour of a fi xed bed considering both intra and inter-pellet diffusion for adsorption of parachloro-meta-xylenol (PCMX)

Abstract Phenols and Phenolics are considered to be potentially hazardous water pollutants. Parachlorometaxylenol (PCMX) is the major component of several disinfectants, produced commercially by well-known pharmaceutical companies. Adsorption of PCMX in various combinations of adsorbents, both natural and artificial, has been studied. Specially, water hyacinth (Eichhornia crassipes [Mart] Solms-Laubach) stems were used as adsorbent in combination with powdered activated carbon (PAC) and granular activated carbon (GAC). Five equilibrium isotherm models, namely, Tempkin Isotherm, Freundlich Isotherm, Langmuir Isotherm, Redlich-Peterson Isotherm and Toth Isotherm were studied and parameterized. The dynamics of fixed-bed adsorption columns for modeling is a demanding task due to the strong nonlinearities in the equilibrium isotherms, interference effects of the competition of solutes for adsorbent sites, mass transfer resistances between fluid phase and solid phase and fluid-dynamic dispersion phenomena. A ma...

Adsorption of para chloro meta xylenol (PCMX) in composite adsorbent beds: Parameter estimation using nonlinear least square technique

Phenols and phenolics are considered to be potentially hazardous water pollutants. Para chloro meta xylenol (PCMX) is the major component of several disinfectants, produced commercially by internationally well-known pharmaceutical companies. Adsorption of PCMX in various combinations of adsorbents, both natural and artificial, has been studied. Specially, water hyacinth ( Eichhornia crassipes [Mart] Solms-Laubach) was used as an adsorbent in combination with powdered activated carbon (PAC) and granular activated carbon (GAC). Prediction of PCMX adsorption capacities is important in design considerations. Various equilibrium adsorption isotherms have been studied using experimental data. Equilibrium was achieved after approximately 24 h. Five isotherm models, namely, Tempkin isotherm, Freundlich isotherm, Langmuir isotherm, Redlich–Peterson isotherm and Toth isotherm were studied and parameterized. Respective parameters for each of the models were estimated by the nonlinear Levenburg–Marquardt parameter estimation method, based on the ( 2 minimization. Model performance was ascertained using uncertainty analysis on both the parameters, k 1 and k 2, for each of the five models. The models were simultaneously ranked. The Tempkin isotherm was ranked 1 in case of all the 3 samples with extremely low uncertainties on both parameters k 1 and k 2. Depending on the nature of the sample and its range of concentration levels, isotherm model by Langmuir scored 2 in the ranking scale on 2 occasions out of 3 with low uncertainties on both k 1 and k 2.