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Prevalence of a koinobiont endoparasitoid Misotermes mindeni (Diptera: Phoridae) in colonies of the fungus-growing termite Macrotermes gilvus (Blattodea: Termitidae) in Malaysia

Foo FK, Singham GV, Othman AS, Lee CY

J Econ Entomol, 2011 Oct;104(5):1675-9.
PMID: 22066198

A survey of the infestation rate of colonies of Macrotermes gilvus (Hagen) (Termitidae: Macrotermitinae) with the koinobiont endoparasitoid Misotermes mindeni Disney & Neoh (Diptera: Phoridae) was conducted in Malaysia from September 2009 to January 2011 in the states of Kedah, Penang, Perak, Selangor, Kuala Lumpur, Johor, Terengganu, and Sarawak. Of the 1,125 M. gilvus mounds surveyed, 12.4% contained termites parasitized by M. mindeni and these mounds occurred only in the states of Penang and Perak. High frequencies of mounds containing parasitized termites were found at sites in Penang: Bayan Lepas (21.1%), Minden Campus of Universiti Sains Malaysia ([USM]; 24.5%), Teluk Bahang (28.0%), and Bukit Mertajam (35.0%); the lowest frequency (4.0%) was recorded from Gelugor. The parasitized colonies at all sites were classified as healthy, with exception of several from the Minden Campus of USM (96.4% healthy) and Ayer Itam (87.5% healthy). Most parasitized colonies (71.2%) had a low level of M. mindeni infestation. Only 16.7 and 12.1% of the infested colonies had moderate or high parasite infestation levels, respectively. The height of infected mounds was significantly higher than that of the healthy mounds, but there was no difference between the mound diameters of infested and uninfested mounds. Parasite infestation level was not significantly correlated with mound height or mound diameter. The ambient light intensity at sites with infested mounds was significantly lower than that of uninfested mounds. There was also a significant negative relationship between light intensity and degree of parasitism.
Differences in Climbing Ability of Cimex lectularius and Cimex hemipterus (Hemiptera: Cimicidae)

Kim DY, Billen J, Doggett SL, Lee CY

J Econ Entomol, 2017 Jun 01;110(3):1179-1186.
PMID: 28334370 DOI: 10.1093/jee/tox039

The climbing abilities of two bed bug species, Cimex lectularius L. and Cimex hemipterus (F.), were determined by evaluating their escape rates from smooth surface pitfall traps using four commercial bed bug monitors (Verifi Bed Bug Detector, ClimbUp Insect Interceptor, BlackOut Bed Bug Detector, and SenSci Volcano Bed Bug Detector). All detectors were used in the absence of lures or attractants. Unlike C. lectularius, adult C. hemipterus were able to escape from all traps. On the other hand, no or a low number nymphs of both species escaped, depending on the evaluated traps. Examination of the vertical friction force of adults of both species revealed a higher vertical friction force in C. hemipterus than in C. lectularius. Scanning electron microscope micrograph observation on the tibial pad of adult bed bugs of C. hemipterus showed the presence of a greater number of tenent hairs on the tibial pad than on that of adult C. lectularius. No tibial pad was found on the fourth and fifth instars of both species. Near the base of the hollow tenent hairs is a glandular epithelium that is better developed in adult C. hemipterus than in adult C. lectularius. This study highlights significant morphological differences between C. lectularius and C. hemipterus, which may have implications in the monitoring and management of bed bug infestations.
Curcumin and a hemi-analogue with improved blood-brain barrier permeability protect against amyloid-beta toxicity in Caenorhabditis elegans via SKN-1/Nrf activation

Lee EH, Lim SS, Yuen KH, Lee CY

J Pharm Pharmacol, 2019 May;71(5):860-868.
PMID: 30515807 DOI: 10.1111/jphp.13052

OBJECTIVES: This study aims to investigate the blood-brain barrier (BBB) permeability of curcumin analogues with shortened linkers and their ability to protect against amyloid-beta toxicity in a whole organism model.
METHOD: Four curcumin analogues were synthesized. These analogues and curcumin were evaluated for their BBB permeability in the parallel artificial membrane permeability assay. The transgenic Caenorhabditis elegansGMC101 that expresses human Aβ1-42 was treated with the compounds to evaluate their ability to delay Aβ-induced paralysis. Expression of skn-1mRNA was examined on nematodes treated with selected efficacious compounds. In vitro Aβ aggregation in the presence of the compounds was performed.
KEY FINDINGS: The four analogues showed improved BBB permeability vs curcumin in the PAMPA with the hemi-analogue C4 having the highest permeability coefficient. At 100 μm, analogues C1 and C4 as well as curcumin significantly prolonged the survival of the nematodes protecting against Aβ toxicity. However, only curcumin and C4 showed protection at lower concentrations. skn-1mRNA was significantly elevated in nematodes treated with curcumin and C4 indicating SKN-1/Nrf activation as a possible mode of action.
CONCLUSIONS: Analogue C4 provides a new lead for the development of a curcumin-based compound for protection against Aβ toxicity with an improved BBB permeability.
Fulltext Penetration mechanics of elongated female and male genitalia of earwigs

Matsumura Y, Kamimura Y, Lee CY, Gorb SN, Rajabi H

Sci Rep, 2021 04 12;11(1):7920.
PMID: 33846369 DOI: 10.1038/s41598-021-86864-1

We unveiled the penile penetration mechanics of two earwig species, Echinosoma horridum, whose intromittent organ, termed virga, is extraordinarily long, and E. denticulatum, whose virga is conversely short. We characterised configuration, geometry, material and bending stiffness for both virga and spermatheca. The short virga of E. denticulatum has a material gradient with the stiffer base, whereas the long virga of E. horridum and the spermathecae of both species are homogeneously sclerotised. The long virga of E. horridum has a lower bending stiffness than the spermatheca. The virga of E. denticulatum is overall less flexible than the spermatheca. We compared our results to a previous study on the penetration mechanics of elongated beetle genitalia. Based on the comparison, we hypothesised that the lower stiffness of the male intromittent organ comparing to the corresponding female structure is a universal prerequisite for the penetration mechanics of the elongated intromittent organ in insects.
Multiple Mechanisms Conferring Broad-Spectrum Insecticide Resistance in the Tropical Bed Bug (Hemiptera: Cimicidae)

Dang K, Doggett SL, Leong XY, Veera Singham G, Lee CY

J Econ Entomol, 2021 12 06;114(6):2473-2484.
PMID: 34693975 DOI: 10.1093/jee/toab205

The modern resurgence of the common (Cimex lectularius L.) and tropical bed bugs (C. hemipterus [F.]) is thought to be primarily due to insecticide resistance. While there are many reports on insecticide resistance mechanisms in C. lectularius, such information in C. hemipterus is limited. We examined dichloro-diphenyl-trichloroethane (DDT), malathion, deltamethrin, permethrin, lambda-cyhalothrin resistance, and the underlying mechanisms in several C. hemipterus strains (Australia: Queensland [QLD-AU]; Malaysia: Kuala Lumpur [KL-MY], Tanjung Tokong [TT-MY], Christian [CH-MY], and Green Lane [GL-MY]). We used a surface contact method, synergism studies (utilizing piperonyl butoxide [PBO], S,S,S-tributyl phosphorotrithioate [DEF], and diethyl maleate [DEM]), and molecular detection of kdr mutations. Results demonstrated that all C. hemipterus strains possessed high resistance to DDT and the pyrethroids and moderate to high resistance to malathion. Synergism studies showed that deltamethrin resistance in all strains was significantly (P < 0.05) inhibited by PBO. In contrast, deltamethrin resistance was not affected in DEF or DEM. Similar findings were found with lambda-cyhalothrin resistance. Malathion resistance was significantly (P < 0.05) reduced by DEF in all strains. Resistance to DDT was not affected by DEM in all strains. Multiple kdr mutations (M918I, D953G, and L1014F) were detected by molecular analyses. TT-MY strain was found with individuals possessing three kdr mutation combinations; D953G + L1014F (homozygous susceptible: M918), M918I + D953G + L1014F (heterozygous resistant: I918), and M918I + D953G + L1014F (homozygous resistant: I918). Individuals with M918I + D953G + L1014F (homozygous resistant: I918) survived longer on deltamethrin (>12 h) than those (≤1 h) with other combinations. M918I + L1014F mutations most likely conferred super-kdr characteristic toward pyrethroids and DDT in C. hemipterus.
Fulltext Circadian rhythms in insecticide susceptibility, metabolic enzyme activity, and gene expression in Cimex lectularius (Hemiptera: Cimicidae)

Khalid MF, Lee CY, Doggett SL, Veera Singham G

PLoS One, 2019;14(6):e0218343.
PMID: 31206537 DOI: 10.1371/journal.pone.0218343

Many insect species display daily variation of sensitivity to insecticides when they are exposed to the same concentration at different times during the day. To date, this has not been investigated in bed bugs. To address this, we explored circadian rhythms in insecticide susceptibility, xenobiotic metabolizing (XM) gene expressions, and metabolic detoxification in the common bed bug, Cimex lectularius. An insecticide susceptible Monheim strain of C. lectularius was most tolerant of deltamethrin during the late photophase at ZT9 (i.e. nine hours after light is present in the light-dark cycle (LD) cycle) and similarly repeated at CT9 (i.e. nine hours into the subjective day in constant darkness (DD)) suggesting endogenous circadian involvement in susceptibility to deltamethrin. No diel rhythm was observed against imidacloprid insecticide despite significant daily susceptibility in both LD and DD conditions. Rhythmic expressions of metabolic detoxification genes, GSTs1 and CYP397A1 displayed similar expression patterns with total GST and P450 enzyme activities in LD and DD conditions, respectively. The oscillation of mRNA levels of GSTs1 and CYP397A1 was found consistent with peak phases of deltamethrin susceptibility in C. lectularius. This study demonstrates that circadian patterns of metabolic detoxification gene expression occur within C. lectularius. As a consequence, insecticide efficacy can vary dramatically throughout a 24 hour period.
Nanorod reassembling on a sprayed SERS substrate under confined evaporation inducing ultrasensitive TPhT detection

Chang L, Liu X, Lee CY, Zhang W

Anal Chim Acta, 2023 Oct 23;1279:341825.
PMID: 37827623 DOI: 10.1016/j.aca.2023.341825

Triphenyltin is an estrogen like pollutant that poses significant environmental threats due to its highly accumulative toxicity. To improve regulation, a fast and sensitive detection method is urgently needed. SERS can capture fingerprint information and is capable of trace detection, making it an ideal solution. Here, we present a sprayed substrate comprised of lightconfining structures and gold nanorod assemblies that are easy to prepare, low-cost, and can form dense hotspots under confined evaporation. The substrates are three-layered: initially, a gold nanorod layer is sprayed as a support, then sputter Ag film on the surface to form a lightconfining structure, followed by another gold nanorod layer sprayed on the Ag film. The coupling of nanorod assembly with lightconfining Ag films leads to 10-fold sensitivity. In addition, sample droplet evaporation in a limited area called confined evaporation contributes to nanorod migration and reassembly on the corner of the substrate, enhancing analytes absorption, and substantially lowered the detection limits. By systematically evaluating the substrate performance, we were able to obtain an average enhancement factor of 3.31 × 106. After confined evaporation, the detection limit reached 10-18 M for R6G and for triphenyltin, it achieved 10-9 M. This novel method represents a significant advancement toward SERS application in detecting trace pollutants.
Fulltext Insecticide resistance and resistance mechanisms in bed bugs, Cimex spp. (Hemiptera: Cimicidae)

Dang K, Doggett SL, Veera Singham G, Lee CY

Parasit Vectors, 2017 Jun 29;10(1):318.
PMID: 28662724 DOI: 10.1186/s13071-017-2232-3

The worldwide resurgence of bed bugs [both Cimex lectularius L. and Cimex hemipterus (F.)] over the past two decades is believed in large part to be due to the development of insecticide resistance. The transcriptomic and genomic studies since 2010, as well as morphological, biochemical and behavioral studies, have helped insecticide resistance research on bed bugs. Multiple resistance mechanisms, including penetration resistance through thickening or remodelling of the cuticle, metabolic resistance by increased activities of detoxification enzymes (e.g. cytochrome P450 monooxygenases and esterases), and knockdown resistance by kdr mutations, have been experimentally identified as conferring insecticide resistance in bed bugs. Other candidate resistance mechanisms, including behavioral resistance, some types of physiological resistance (e.g. increasing activities of esterases by point mutations, glutathione S-transferase, target site insensitivity including altered AChEs, GABA receptor insensitivity and altered nAChRs), symbiont-mediated resistance and other potential, yet undiscovered mechanisms may exist. This article reviews recent studies of resistance mechanisms and the genes governing insecticide resistance, potential candidate resistance mechanisms, and methods of monitoring insecticide resistance in bed bugs. This article provides an insight into the knowledge essential for the development of both insecticide resistance management (IRM) and integrated pest management (IPM) strategies for successful bed bug management.
Biochemical characterization of insecticide resistance in the German cockroach, Blattella germanica, from Malaysia

Lee CY, Hemingway J, Yap HH, Chong NL

Med Vet Entomol, 2000 Mar;14(1):11-8.
PMID: 10759307

The possible insecticide resistance mechanisms of four Malaysian field-collected strains of the German cockroach, Blattella germanica (Linnaeus) (Dictyoptera: Blattellidae), were characterized with biochemical assays and native polyacrylamide gel electrophoresis (PAGE). Elevated esterase activity (at low to moderate frequency) and altered acetylcholinesterase (low frequency) were detected in all field strains, while elevated glutathione S-transferase levels were present in only two strains. Seven esterase bands were separated by native PAGE; a greater intensity occurred in three bands in the resistant strains compared to the susceptible strain. Inhibition studies using specific inhibitors on polyacrylamide gels suggested that the slowest of these three esterases is a cholinesterase, while the other two are carboxylesterases with a preference for beta- over alpha-naphthyl acetate.
Subterranean termite open-air foraging and tolerance to desiccation: Comparative water relation of two sympatric Macrotermes spp. (Blattodea: Termitidae)

Hu J, Neoh KB, Appel AG, Lee CY

Comp Biochem Physiol A Mol Integr Physiol, 2012 Feb;161(2):201-7.
PMID: 22085890 DOI: 10.1016/j.cbpa.2011.10.028

The foraging patterns of termites are strongly related to physiological limits in overcoming desiccation stress. In this study, we examined moisture preferences and physiological characteristics of Macrotermes carbonarius (Hagen) and M. gilvus (Hagen) as both exhibit conspicuous patterns of foraging activity. Despite both species showing no significant differences in calculated cuticular permeability, and percentage of total body water, they differed greatly in rate of water loss and surface area to volume ratio. For example, M. carbonarius which had a lower surface area to volume ratio (29.26-53.66) showed lower rate of water loss and percentage of total body water loss. This also resulted in higher LT(50) when exposed to extreme conditions (≈2% RH). However, contrasting observations were made in M. gilvus that has smaller size with higher surface area to volume ratio of 40.28-69.75. It is likely that the standard equation for calculating insect surface areas is inadequate for these termite species. The trend was further supported by the result of a moisture preference bioassay that indicated M. carbonarius had a broader range of moisture preference (between 5% and 20%) than M. gilvus which had a relatively narrow moisture preference (only 20%). These results explain why M. carbonarius can tolerate desiccation stress for a longer period foraging above-ground in the open air; while M. gilvus only forages below ground or concealed within foraging mud tubes.
Fulltext Identification and reproductive isolation of Euborellia species (Insecta, Dermaptera, Anisolabididae) from East and Southeast Asia

Kamimura Y, Lee CY, Yamasako J, Nishikawa M

Zookeys, 2023;1146:115-134.
PMID: 37214591 DOI: 10.3897/zookeys.1146.98248

Euborellia (Anisolabididae: Anisolabidinae) is one of the most speciose genera of earwigs (Dermaptera), and its species-level classification is difficult. To settle the classification of brachypterous species with abbreviated tegmina recorded from East and Southeast Asia, we examined the morphology and reproductive isolation of three tentative Euborellia species, and analyzed the DNA barcoding region of the mitochondrial cytochrome oxidase subunit I (COI) gene. The observed complete reproductive isolation among the three Euborellia taxa and considerable differentiation in the COI sequences clearly show that each should be treated as a separate species. Based on morphology, distribution and the DNA sequence, we identify Euborellia sp. 1 of Malaysia as E.annulata (Fabricius), a circumtropical cosmopolitan with no records of a fully winged form. Samples from Ioto Island (= Iwo-jima Island: Ogasawara Islands, southern Japan) were also identified as this species. Euborellia sp. 3, from the main islands of Japan, was generally larger and lacked a Y-shaped pigmented area on the penis lobe, which is characteristic of Euborellia sp. 1. We propose reinstating E.pallipes (Shiraki) as the oldest name for this taxon. Euborellia sp. 2, even the brachypterous form, can be distinguished from these two species by its paler coloration (particularly the femora), ecarinate post-abdomen, and the shape of the male genitalia (parameres). We tentatively identify this species as E.philippinensis Srivastava based on the morphology of the brachypterous form, although the macropterous form cannot be distinguished from E.femoralis (Dohrn).
Fulltext A Missed Late Presentation of a Congenital Pulmonary Airway Malformation as a Large Infected Bulla

Lee CY, Osman SS, Noor HM, Isa NSA

Sultan Qaboos Univ Med J, 2018 Nov;18(4):e541-e544.
PMID: 30988978 DOI: 10.18295/squmj.2018.18.04.020

A congenital pulmonary airway malformation (CPAM) is a rare cystic anomaly that may occur during development of the fetal airways. The vast majority of CPAMs are detected in neonates; as such, it is unusual for diagnosis to occur in adulthood. We report a 21-year-old male patient who presented to the emergency department of the Hospital Ampang, Kuala Lumpur, Malaysia, in 2015 with chest pain, breathlessness and tachypnoea. Based on an initial chest X-ray, the patient was misdiagnosed with pneumothorax and underwent urgent chest tube insertion; however, his condition deteriorated over the course of the next three days. Further imaging was suggestive of infected bullae or an undiagnosed CPAM. The patient therefore underwent video-assisted thoracoscopic surgery, during which a large infected bulla was resected. A diagnosis of an infected CPAM was confirmed by histopathological examination. Following the surgery, the patient recovered quickly and no bullae remnants were found at a one-month follow-up.
Fulltext Field-simulated residual efficacy of betacyfluthrin against Anopheles sinensis Wiedemann

Yap HH, Chong NL, Lee CY, Koay CA

Southeast Asian J Trop Med Public Health, 1997 Mar;28(1):233-4.
PMID: 9322312

The residual efficacy of a relatively new pyrethroid, betacyfluthrin was compared with DDT against Anopheles sinensis Wiedemann in some village houses in Penang, Malaysia, for a period of 30 weeks. Efficacy was determined by exposing laboratory-cultured An. sinensis mosquitos to treated wall surfaces with either betacyfluthrin at 15 and 25 mg/m2 or DDT at 2,000 mg/m2 for one hour. Betacyfluthrin provided a longer residual effect (up to 210 days with > 70% mortality) compared with DDT. The potential of betacyfluthrin as a candidate for residual spraying for malaria control is discussed.
A review of the use of Piper betel in oxidative stress disorders

Lee CY, Nurul Zaidah AS, Nur Amalina G, Muhammad Azree E, Das S, Zar CT

Clin Ter, 2014;165(5):269-77.
PMID: 25366948 DOI: 10.7417/CT.2014.1758

Increase in prevalence of disease related oxidative stress disorders have been on the rise in the entire world since the past decades. Significant positive effects with few antioxidant properties in the modern drugs pave for the alternative medicines in managing the disease. Piper betel (P. betel), a herb, is known to possess high anti-oxidant, anti-diabetic, anti-atherosclerosis, anti-hyperlipidemic, anti-cancer and neuroprotective property. This review focused on the effect of P. betel on diabetes mellitus, atherosclerosis and chronic kidney disease, Alzheimer's disease and breast cancer. P. betel proved to show positive effects with specific outcomes towards these diseases. Moreover, the promising effect of P. betel in vitro studies was also highlighted in the present review. It is believed that the findings obtained in this review will draw the attention of the medical professionals and general public towards P. betel and it will open the door for further detailed research.
Fulltext Insecticide resistance and its underlying mechanisms in field populations of Aedes aegypti adults (Diptera: Culicidae) in Singapore

Koou SY, Chong CS, Vythilingam I, Lee CY, Ng LC

Parasit Vectors, 2014;7:471.
PMID: 25301032 DOI: 10.1186/s13071-014-0471-0

In Singapore, dose-response bioassays of Aedes aegypti (L.) adults have been conducted, but the mechanisms underlying resistance to insecticides remain unclear. In this study, we evaluated insecticide resistance and its underlying mechanism in field populations of Ae. aegypti adults.
Pyrethroid resistance in Aedes aegypti larvae (Diptera: Culicidae) from Singapore

Koou SY, Chong CS, Vythilingam I, Ng LC, Lee CY

J Med Entomol, 2014 Jan;51(1):170-81.
PMID: 24605467

We report the first comprehensive insecticide susceptibility status ofAedes aegypti (L.) larvae from Singapore. The study indicated that Ae. aegypti is susceptible to temephos, although resistance (RR50 = 1.29-4.43-fold) couldbe developing. Of high concern is the detection of moderate to high resistance to permethrin (RR50 = 29-47-fold) and etofenprox (RR50 = 14-34-fold). Biolarvicide Bacillus thuringiensis israelensis (Bti) remains effective. The insecticide susceptibility profile of Ae. aegypti larvae was found to be homogenous among the different sites studied across the island city. The addition of synergists piperonyl butoxide, S,S,S,-tributyl phosphorotrithioate, and triphenyl phosphate generally failed to enhance the toxicity of the insecticides investigated, suggesting an insignificant role of metabolic-based resistance, and a possible involvement of target site resistance. Further biochemical investigation of specific metabolic enzyme activities suggested that detoxifying enzymes, mono-oxygenases, esterases, glutathione S-transferases, and altered acetylcholinesterases, generally did not contribute to the resistance observed. This study clearly demonstrated that pyrethroid resistance is widespread among Ae. aegypti population and lowered susceptibility to organophosphates is developing.
Fulltext Do termites avoid carcasses? Behavioral responses depend on the nature of the carcasses

Neoh KB, Yeap BK, Tsunoda K, Yoshimura T, Lee CY

PLoS One, 2012;7(4):e36375.
PMID: 22558452 DOI: 10.1371/journal.pone.0036375

Undertaking behavior is a significant adaptation to social life in enclosed nests. Workers are known to remove dead colony members from the nest. Such behavior prevents the spread of pathogens that may be detrimental to a colony. To date, little is known about the ethological aspects of how termites deal with carcasses.
Polymorphic microsatellite loci from an indigenous Asian fungus-growing termite, Macrotermes gilvus (Blattodea: Termitidae) and cross amplification in related taxa

Singham GV, Vargo EL, Booth W, Othman AS, Lee CY

Environ Entomol, 2012 Apr;41(2):426-31.
PMID: 22507019 DOI: 10.1603/EN11228

The fungus-growing termite, Macrotermes gilvus (Hagen), an indigenous species from Southeast Asia distributed from Myanmar to Indonesia and the Philippines, offers great potential as an ecological model system to elucidate the effects of geography on gene flow within this region. We used next generation sequencing (Roche 454 pyrosequencing) to identify microsatellite markers from the genomic DNA of M. gilvus. A modest sequencing volume generated 34,122 reads, with 1,212 (3.6%) reads contains microsatellites with di-, tri-, tetra-, penta-, and hexa-nucleotide repeat motifs. Thirty-seven loci were selected for primer development and tested for polymorphism across 22 colonies of M. gilvus. Eleven loci were found to be polymorphic with 2-4 alleles per locus. Observed and expected heterozygosities ranged between 0.091-0.727 and 0.090-0.540, respectively. Cross taxa amplification was successful across a panel of four related termite species and four multiplex groups were designed for future population genetic studies. These markers will open new avenues for the study of phylogeography and population genetics of this fungus-growing termite. This study also has effectively demonstrated the use of 454 pyrosequencing for the rapid development of informative microsatellite markers from a termite genome.
Fulltext Clinical and laboratory analysis of influenza B infection in children in Taichung, Taiwan during the 2006-2007 flu season

Wang CC, Chen PY, Wang JD, Liu FC, Huang FL, Lee CY

Pediatr Neonatol, 2009 Apr;50(2):54-8.
PMID: 19453079 DOI: 10.1016/S1875-9572(09)60033-4

An epidemic of influenza B/Malaysia/2506/2004 was reported in Taiwan during the 2006-2007 flu season. We investigated the flu vaccination history and clinical and Laboratory characteristics of children with influenza B infection.
Electrochemical-assisted photodegradation of mixed dye and textile effluents using TiO2 thin films

Zainal Z, Lee CY, Hussein MZ, Kassim A, Yusof NA

J Hazard Mater, 2007 Jul 19;146(1-2):73-80.
PMID: 17196740

Mixed dye consists of six commercial dyes and textile effluents from cotton dyeing process were treated by electrochemical-assisted photodegradation under halogen lamp illumination. Two types of effluents were collected which are samples before and after undergone pre-treatment at the factory wastewater treatment plant. The photodegradation process was studied by evaluating the changes in concentration employing UV-vis spectrophotometer (UV-vis) and total organic carbon (TOC) analysis. The photoelectrochemical degradation of mixed dye was found to follow the Langmuir Hinshelwood pseudo-first order kinetic while pseudo-second order kinetic model for effluents by using TOC analyses. The chemical oxygen demand (COD) and biochemical oxygen demand (BOD) values of mixed dye and raw effluents were reported. Photoelectrochemical characteristic of pollutants was studied using the cyclic voltammetry technique. Raw effluent was found to exhibit stronger reduction behaviour at cathodic bias potential but slightly less photoresponse at anodic bias than mixed dye.

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