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Photocatalytic decolourisation of Reactive Red 4 dye by an immobilised TiO2/chitosan layer by layer system

Nawi MA, Sabar S, Sheilatina

J Colloid Interface Sci, 2012 Apr 15;372(1):80-7.
PMID: 22321991 DOI: 10.1016/j.jcis.2012.01.024

The synergistic photocatalysis-adsorption processes by the immobilized TiO(2)/chitosan layer by layer system on a glass support (TiO(2)/CS/glass) were investigated for the decolourisation of Reactive Red 4 (RR4) dye solution. Effects of different reaction parameters such as TiO(2) loading, initial pH of the solution, visible light, dissolved oxygen and radical quenchers were studied. The decolourisation rate of RR4 by TiO(2)/CS/glass was more than 32 times faster than a single layer of TiO(2) but was highly dependent on the TiO(2) loading and the initial pH of the solution. A thin layer of TiO(2) and acidic conditions favoured the adsorption of RR4 at the TiO(2)/CS interface. The h(+)/OH() species that diffused from the TiO(2) layer into the TiO(2)/CS interface oxidised the chemisorbed RR4 anions at the interface, and the generated electrons were then transferred to the conduction band of TiO(2). Excess electrons in the conduction band of TiO(2) increased the number of superoxide ions produced and thus improved the photocatalytic decolourisation of RR4. Therefore, apart from the synergistic photocatalysis-adsorption processes, a charge transfer process was also found to be responsible for maintaining the efficiency, sustainability and reusability of the TiO(2)/CS/glass layer by layer system.
Oxidation of crosslinked chitosan-epichlorohydrine film and its application with TiO2 for phenol removal

Jawad AH, Nawi MA

Carbohydr Polym, 2012 Sep 1;90(1):87-94.
PMID: 24751014 DOI: 10.1016/j.carbpol.2012.04.066

Photocatalytic oxidation of crosslinked chitosan-epichlorohydrin (CS-ECH) film was successfully achieved via an immobilized TiO2/CS-ECH photocatalyst system on a glass plate. Oxidation process of CS-ECH film was carried out by irradiating the system with a 45-W fluorescent lamp for 10h in ultra-pure water. The results indicate the formation of carbonyl functional groups and partial elimination of amine groups in the molecular structure of the oxidized CS-ECH film. This oxidized CS-ECH film has different optical properties, ionic conductivity, degree of transparency, swelling index and chemical stability than the fresh CS-ECH film. In the environmental applications, the TiO2/oxidized-CS-ECH photocatalyst system can have photodegradation and faster mineralization rate of phenol than both fresh TiO2/CS-ECH and TiO2/oxidized-CS photocatalyst systems. This simple photocatalyst system, therefore can be considered as an environmental friendly method to oxidize synthetic biopolymer and to improve the photocatalytic efficiency of TiO2 to treat wastewater.
Insight into the synergistic photocatalytic-adsorptive removal of methyl orange dye using TiO2/chitosan based photocatalyst

Bahrudin NN, Nawi MA, Zainal Z

Int J Biol Macromol, 2020 Dec 15;165(Pt B):2462-2474.
PMID: 33736271 DOI: 10.1016/j.ijbiomac.2020.10.148

The removal of methyl orange (MO) dye has been studied using TiO2/chitosan-montmorillonite (TiO2/Cs-MT) bilayer photocatalyst which also functions as an adsorbent. The dye removal experiments were conducted in the dark and under UV-Vis light irradiation via adsorption and photocatalysis-adsorption processes, respectively. The adsorption modelings were employed on the dark experimental data and compared with the immobilized and suspended Cs-Mt counterparts. It was found that the bilayer photocatalyst closely followed the adsorption properties of immobilized Cs-Mt which obeyed the pseudo-second-order kinetic and film diffusion models. Fluorescent analysis revealed that the charge separation was enhanced in the presence of Cs-Mt as a sub-layer of TiO2. Under light irradiation, the photocatalytic activity of TiO2/Cs-MT corresponded to its adsorption counterpart trend and was optimized at pH 6.5 and 20 mg L-1 of MO dye solution. High removal efficiency and synergism of MO by TiO2/Cs-MT over TiO2 single layer were observed throughout the 10 cycles of application due to contribution of adsorption of Cs-Mt sub-layer and photocatalysis by TiO2 top layer.
Newly developed baffled subsurface-flow constructed wetland for the enhancement of nitrogen removal

Tee HC, Lim PE, Seng CE, Nawi MA

Bioresour Technol, 2012 Jan;104:235-42.
PMID: 22130081 DOI: 10.1016/j.biortech.2011.11.032

The objectives of this study are to compare the performance of newly developed baffled and conventional horizontal subsurface-flow (HSF) constructed wetlands in the removal of nitrogen at the hydraulic retention times (HRT) of 2, 3 and 5 days and to evaluate the potential of rice husk as wetland media for wastewater treatment. The results show that the planted baffled unit achieved 74%, 84% and 99% ammonia nitrogen (NH(4)(+)-N) removal versus 55%, 70% and 96% for the conventional unit at HRT of 2, 3 and 5 days, respectively. The better performance of the baffled unit was explained by the longer pathway due to the up-flow and down-flow conditions sequentially thus allowing more contact of the wastewater with the rhizomes and micro-aerobic zones. Near complete total oxidized nitrogen was observed due to the use of rice husk as wetland media which provided the COD as the electron donor in the denitrification process.
Enhanced decolourization of methyl orange by immobilized TiO2/chitosan-montmorillonite

Bahrudin NN, Nawi MA, Zainal Z, Schneider R, Sabar S

Water Sci Technol, 2020 Aug;82(3):454-467.
PMID: 32960791 DOI: 10.2166/wst.2020.349

Many attempts have been made to improve the photocatalytic performance of immobilized photocatalysts for large-scale applications by modification of the photocatalyst properties. In this work, immobilized bilayer photocatalyst composed of titanium dioxide (TiO2) and chitosan-montmorillonite (CS-MT) were prepared in a layer-by-layer arrangement supported on glass substrate. This arrangement allows a simultaneous occurrence of adsorption and photocatalysis processes of pollutants, whereby each layer could be independently modified and controlled to acquire the desired degree of occurring processes. It was found that the addition of MT clay within the CS composite sub-layer improved the mechanical strength of CS, reduced its swelling and shifted its absorption threshold to higher wavelengths. In addition, the band gap energy of the photocatalyst was also reduced to 2.93 eV. The immobilized TiO2/CS-MT exhibited methyl orange (MO) decolourization rate of 0.071 min-1 under light irradiation, which is better than the single TiO2 due to the synergistic processes of adsorption by CS-MT and photocatalysis by TiO2 layer. The MO dye took 6 h to achieve complete mineralization and produced sulfate and nitrate ions as the by-products. Furthermore, the immobilized TiO2/CS-MT could be reused for at least ten cycles of application without significant loss of its activity.
Fulltext Prevalence and pattern of third molars impaction: A retrospective radiographic study

Shaari RB, Awang Nawi MA, Khaleel AK, AlRifai AS

J Adv Pharm Technol Res, 2023;14(1):46-50.
PMID: 36950463 DOI: 10.4103/japtr.japtr_489_22

Third molar impaction is considered a prevalent issue. The research aimed to study the pervasiveness and pattern of impaction in Karbala/Iraqi population. Orthopantomograms were studied regarding its angulation, impaction depth, and correlation with ramus. The outcomes manifested that the prevalence of 3rd impacted molars was 34.71%, with the proportion of male to female as 0.83:1. Impacted mandibular 3rd molars were significantly encountered. The prevalence of vertical angulation, mesioangular, horizontal, and inverted were significantly associated with the impacted mandibular 3rd molars (P < 0.05). However, the prevalence of distoangular and bucco/lingual was significantly associated (P < 0.05) with the upper impacted 3rd molars. Level C of impaction was significantly (P < 0.05) the most typical level in the maxilla impacted the 3rd molar, and level A and level B of impaction were significantly (P < 0.05) the most prevalent level correlated with the mandibular 3rd molar impaction. Class II was significantly (P < 0.05) the frequently occurring condition subsequent to Classes III and I. In conclusion, the impaction of 3rd molars was significantly predominant in females and lower jaw. The vertical angulation, level C of impaction associated with maxillary 3rd molars and levels A and B of impaction related with mandibular 3rd molars, and Class II are the most encountered conditions.
Enhancement of azo dye Acid Orange 7 removal in newly developed horizontal subsurface-flow constructed wetland

Tee HC, Lim PE, Seng CE, Mohd Nawi MA, Adnan R

J Environ Manage, 2015 Jan 1;147:349-55.
PMID: 25284799 DOI: 10.1016/j.jenvman.2014.09.025

Horizontal subsurface-flow (HSF) constructed wetland incorporating baffles was developed to facilitate upflow and downflow conditions so that the treatment of pollutants could be achieved under multiple aerobic, anoxic and anaerobic conditions sequentially in the same wetland bed. The performances of the baffled and conventional HSF constructed wetlands, planted and unplanted, in the removal of azo dye Acid Orange 7 (AO7) were compared at the hydraulic retention times (HRT) of 5, 3 and 2 days when treating domestic wastewater spiked with AO7 concentration of 300 mg/L. The planted baffled unit was found to achieve 100%, 83% and 69% AO7 removal against 73%, 46% and 30% for the conventional unit at HRT of 5, 3 and 2 days, respectively. Longer flow path provided by baffled wetland units allowed more contact of the wastewater with the rhizomes, microbes and micro-aerobic zones resulting in relatively higher oxidation reduction potential (ORP) and enhanced performance as kinetic studies revealed faster AO7 biodegradation rate under aerobic condition. In addition, complete mineralization of AO7 was achieved in planted baffled wetland unit due to the availability of a combination of aerobic, anoxic and anaerobic conditions.
Fulltext Caring for a child with cancer during COVID-19 pandemic: an assessment of the parents' perception and stress level

Nawi MA, Lau SCD, Chin ST, Teh KH, Ho LSB, Alias H

Front Public Health, 2024;12:1223362.
PMID: 38655523 DOI: 10.3389/fpubh.2024.1223362

BACKGROUND: The emergence of COVID-19 pandemic has led to heightened fear and uncertainty among parents of children with cancer. This study was conducted to evaluate the parental perceptions toward effects of COVID-19 infection to children with cancer, determine their stress level and factors contributing to high stress level during the pandemic.
METHODS: This cross-sectional study was conducted in three paediatric oncology centres in Malaysia from September 2020 until December 2022. A total of 167 parents were recruited. Parents completed a set of questionnaires to assess their perception on effect of COVID-19 infection to children with cancer and COVID Stress Scale (CSS) to assess the parents' stress level.
RESULTS: Patients' mean age at study entry was 8.75 years (SD 4.38). Ninety-one (54.5%) patients were still on active treatment. More than 80% of the parents obtained information regarding COVID-19 infection from mass media and social networking. Fear of their children contracting COVID-19 infection was high especially among patients who were still on treatment. Forty-nine (29.3%) parents were significantly affected by the pandemic leading to loss of job or monthly income. Twenty-nine (17.4%) patients required treatment modification during the pandemic. The median total score for CSS was 78.0 (IQR 25th 64.0; 75th 95.0). Ninety-one (54.5%) respondents were very/extremely stressed based on the CSS scores. Components with high scores were xenophobia (median score 18.0; IQR 25th 13.0, 75th 22.0), fear of danger (median score 17.0; IQR 25th 14.0, 75th 20.0) and contamination fears (median score 16.0; IQR 25th 12.0, 75th 19.0). Lower household income was associated with higher stress level (p = 0.006).
CONCLUSION: Our study demonstrated high awareness regarding risk of COVID-19 infection among parents of oncology children. Half of the parents had high stress level, with low household income identified as a factor associated with high stress level.
Fulltext Association of Vital Pulp Therapy Outcomes with Tooth Type, Arch Location, Treatment Type, and Number of Surfaces Destroyed in Deciduous Teeth: A Retrospective Study

Maqbool M, Noorani TY, Samsudin NA, Awang Nawi MA, Rossi-Fedele G, Karobari MI, et al.

Int J Environ Res Public Health, 2021 07 28;18(15).
PMID: 34360261 DOI: 10.3390/ijerph18157970

There is a paucity of information concerning vital pulp treatment outcomes in the undergraduate teaching setting. This study aimed to determine which type of deciduous molar, arch location, type of vital pulp therapy, and the number of carious surfaces involved had a better prognosis when carried out by undergraduate dental students. The method used was the review of clinical records of 590 patients with 600 deciduous molars, that visited the outpatient undergraduate dental clinics for vital pulp therapy. Statistical analysis used to determine the associations of tooth type, arch location, treatment type, and the number of carious surfaces involved in successful outcomes was logistic regression analysis with significance set at p < 0.05. According to the regression analysis model results, there was a significant association based on tooth type (p < 0.05) and arch location (p = 0.003). In addition, there was a significant association based on the type of treatment performed (p = 0.036). However, there was no significant association in success rates based on the number of carious surfaces involved (p = 0.873). In conclusion, second deciduous molars and maxillary deciduous molars had a better overall prognosis, and indirect pulp therapy was revealed to be more highly associated with successful treatment outcomes in comparison to ferric sulfate pulpotomy in our setting.