The Re(I) complex, [Re(PyPzH)(CO)3
Cl] where PyPzH = 2-(1H-pyrazol-3-yl)pyridine, was successfully synthesised
and characterised with an infrared (IR), ultraviolet-visible (UV-Vis), 1
H and 13C nuclear magnetic resonance (NMR)
spectroscopies and X-ray crystallography. The IR spectrum featured three n(C≡O), n(N-H), n(C=N) and n(C=C) signals
at (1860-2020), 3137, 1614 and 1513 cm-1, respectively. The UV-Vis spectrum of the complex exhibited ligand-centred
(π®>*) electronic excitations [λmax = 227 nm, ε = 1.942 x 104 M-1cm-1; lmax = 292 nm, ε = 0.853 x 104 M-1cm-1] and
a metal-to-ligand charge transfer (MLCT) band [lmax = 331 nm, ε = 0.467 x 104 M-1cm-1]. The 13C and 1
H-NMR spectra
exhibited the characteristic signals of the three C≡O (189.0 – 199.0 ppm) and NH (14.84 ppm), respectively. The X-ray
structure of [Re(PyPzH)(CO)3
Cl] showed the crystal adopted a monoclinic system with a C2/c space group [unit cell
dimensions: a = 27.7422(14) Å, b = 11.1456(5) Å, c = 9.2461(4) Å with α = γ = 90º and β = 92.552(2)º]. Density
functional theory (DFT) and time-dependent (TD) DFT calculations were performed to investigate the optimised structural
geometry and electronic properties of the title complex. The results showed that the highest-occupied molecular orbital
(HOMO) was predominantly found on the dπ-orbitals of Re(I), Cl and CO. While the lowest-unoccupied molecular orbital
(LUMO) was located on the PyPzH moiety. The structural and photophysical properties of the [Re(PyPzH)(CO)3
Cl] were
established and the reaction enthalpies for the dissociation of Cl atom in the formation of [Re(PyPzH)(CO)3
]•
were
discussed in view of its potential application for photocatalytic CO2
reduction.
Biofloc technology improves water quality and promote the growth of beneficial bacteria community in shrimp culture. However, little is known about the bacteria community structure in both water and gut of cultured organisms. To address this, the current study characterised the metagenomes derived from water and shrimp intestine samples of novel Rapid BFTTM with probiotic and clearwater treatments using 16S V4 region and full length 16S sequencing. Bacteria diversity of water and intestine samples of Rapid BFTTM and probiotic treatments were similar. Based on the 16S V4 region, water samples of >20 μm biofloc had the highest abundance of amplicon sequence variant (ASV). However, based on full length 16S, no clear distinction in microbial diversity was observed between water samples and intestine samples. Proteobacteria was the most abundant taxon in all samples based on both 16S V4 and full length 16S sequences. Vibrio was among the highest genus based on 16S V4 region but only full length 16S was able to discern up to species level, with three Vibrios identified-V. harveyi, V. parahaemolyticus and V. vulnificus. Vibrio harveyi being the most abundant species in all treatments. Among water samples, biofloc water samples had the lowest abundance of all three Vibrios, with V. vulnificus was present only in bioflocs of <20 μm. Predicted functional profiles of treatments support the beneficial impacts of probiotic and biofloc inclusion into shrimp culture system. This study highlights the potential displacement of opportunistic pathogens by the usage of biofloc technology (Rapid BFTTM) in shrimp culture.
Redox polymerization of acrylonitrile (AN) with ethyl acrylate (EA) and fumaronitrile (FN), as comonomer and termonomer respectively, were carried out using sodium bisulfite (SBS) and potassium persulphate (KPS) as initiators at 40°C. The actual composition of monomers in copolymers and terpolymers has been characterized by gas chromatography (GC). The effects of EA and FN on the glass transition temperature (Tg) and stabilization temperature have been studied by Differential Scanning Calorimetry (DSC). The degradation behaviour and char yield were obtained by thermogravimetric analysis. Meanwhile, incorporation of 10 mol% of EA in homoPAN system was found to greatly reduce Tg to 66°C as compared to that of the homoPAN (Tg=105°C). The initial cyclization temperature (Ti) was found to be higher (264°C) in comparison to that of homoPAN (246°C). In addition, the incorporation of EA was also shown to reduce the char yield of copolymer to 40%. When FN was incorporated as termonomer, the char yield of poly(AN/EA/ FN) 90/4/6 increased up to 44% after the heat treatment with the lowest Ti (241°C).
Komposit UPR/LNR/gentian kaca telah disediakan dengan menggunakan resin poliester tak tepu daripada hasil pengitaran semula bahan buangan PET. Kajian dimulai dengan pengitaran semula botol minuman PET melalui proses glikolisis dan hasilnya ditindakbalaskan dengan maleik anhidrida untuk mendapatkan resin poliester tak tepu. Kajian diteruskan dengan penyediaan adunan resin poliester tak tepu (UPR) dengan cecair getah asli (LNR) iaitu komposisi penambahan LNR ke dalam UPR telah diubah dari 0-7.5% (wt). Komposisi UPR/LNR dengan sifat mekanik terbaik dipilih sebagai matrik untuk penyediaan komposit berpenguat gentian kaca. Rawatan silana ke atas gentian kaca turut dilakukan dengan menggunakan (3-Aminopropil)triethoxysilane. Hasil daripada kajian mendapati adunan UPR/LNR dengan penambahan 2.5% LNR mempunyai sifat mekanik dan morfologi terbaik dengan partikel-partikel getah yang bersaiz kecil dapat tersebar dengan sekata dalam UPR. Kajian juga menunjukkan berlakunya peningkatkan dalam nilai tegasan, modulus regangan dan kekuatan hentaman bagi komposit UPR/LNR/gentian kaca terawat berbanding dengan penggunaan gentian tanpa rawatan.
In this study, poly(ethylene terephthalate) (PET) wastes bottle was recycled by glycolysis process using ethylene glycol. The unsaturated polyester resin (UPR) was then prepared by reacting the glycolysed product with maleic anhydride. The blend of UPR based on recycled PET wastes with liquid natural rubber (LNR) was carried out by varying the amount of LNR from 0 to 7.5 wt%. Mechanical tests such as tensile and impact were conducted to investigate the effects of LNR on the mechanical properties. Scanning Electron Microscopy (SEM) was used to analyze the morphology of the breaking area resulted from the tensile tests on the UPR and blend samples. From the results, the blend of 2.5 wt% LNR in UPR based recycled PET wastes achieved the highest strength in the mechanical properties and showed a well dispersed of elastomer particles in the sample morphology compared to other blends concentrations. This blend sample was then compared to the optimum blend of LNR with commercial resin through the glass transition temperature value Tg, mechanical strength and morphology properties. The comparison study showed that the Tg for UPR based recycled PET was higher than the value represented from commercial resin due to the degree of crystalinity in the molecular structure of the materials. LNR was found to be an effective impact modifier which gave a greater improvement in UPR from recycled PET wastes structure but not to the commercial one which needs 5% LNR to achieve the optimum properties. Thus, the compatibility between the UP resin based recycled PET and LNR was much better than with the commercial resin.
Surface modification of rice husk (RH) with alkali pre-treatment (NaOH solution 5% w/v) was carried out at the initial state to investigate the effect of surface treatment of fibre on the surface interaction between fibre and rubber. Further modification of RH surfaces after alkali treatment was using Liquid Epoxidized Natural Rubber (LENR) coating at three concentrations, 5%, 10%, and 20% wt LENR solution in toluene. Interfacial morphology and chemical reactions between RH fibre and rubber were analyzed by FTIR and Scanning Electron Microscope (SEM). It was found that 10% wt LENR solution gave the optimum interaction between fibre and rubber. Matrix and composite blends derived from 60% natural rubber (NR), 40% high density polyethylene (HDPE) reinforced with RH fibre were prepared using an internal mixer (Brabender Plasticoder). Result showed that pre-treatment of RH treated with 5% NaOH followed by treatment with 10% LENR solution given the maximum interaction between fibre and matrix that gave rise to better mechanical properties of the composites.
In this research, a novel method was performed to obtain hydrogel with superior thermal stability by incorporation
of cellulose nanocrystals (CNC) into gelatin based hydrogel. Glutaraldehyde was used as cross-linker due to its high
chemical reactivity towards NH2
group on gelatin. Different ratio of gelatin/CNC hydrogel was produced in order to study
the effects of CNC towards the swelling behaviour and thermal stability of gelatin based hydrogel. The obtained hydrogel
was subjected to Fourier transform infrared (FTIR) to verify that gelatin had been cross-linked, swelling test with different
pH for swelling behaviour and thermogravimetric analysis (TGA) for thermal stability. The presence of C=N stretching
group in the FTIR spectrum for gelatin/CNC hydrogel indicated that the cross-linking reaction between gelatin monomer
had been successfully carried out. The hydrogel showed impressive pH sensitivity and maximum swelling was obtained
at pH3. The TGA results clearly showed that the incorporation of CNC into gelatin was able to produce hydrogel with
higher thermal stability compare to neat gelatin.
Coconut fibre reinforced composite was prepared by blending unsaturated polyester resin (UPR) from waste PET with 0.3 v% of coconut fibre. The coconut fibres were pre-treated with sodium hydroxide followed by silane prior to inclusion into the UPR. The untreated coconut fibres reinforced composite were used as a control. Dricon® as a phosphate type of flame retardant was then added to the composite to reduce the flammability of the composite. The amount of Dricon® was varied from 0 to 10 wt% of the overall mass of resin. The burning properties and limiting oxygen index (LOI) of the treated and untreated composites increased with the addition of Dricon®. The tensile strength and modulus of both composites were also increased with the addition of Dricon®. The treated fibre composite with 5 wt% Dricon® showed the highest burning time and LOI with the values of 101.5 s and 34 s, respectively. The optimum tensile strength and modulus for treated fibre composite was at 5 wt% Dricon® whereas the untreated fibre composite was at 2.5 wt% loading of Dricon®. Thermogravimetry (TGA) analysis indicated that the degradation temperature increased with the addition of Dricon® up to 5 wt% into UPR/coconut fibre composites. Morphological observations indicated better distribution of Dricon® for treated fibre composite resulted in enhancement of the tensile properties of the treated fibre composite.
Kajian ini telah menilai kesan pelbagai faktor persekitaran terhadap darjah pengembungan hidrogel selulosa bakteria-asid akrilik. Campuran akues selulosa bakteria-asid akrilik (4:1) telah disediakan dan didedahkan dengan irradiasi alur elektron pada 35 kGy dan 50 kGy. Kadar pengembungan di bawah pengaruh pH, suhu dan kekuatan ionik telah dikaji dari 1 hingga 24 jam. Darjah pengembungan hidrogel bergantung kepada dos irradiasi yang diberi: hidrogel yang telah disintesis pada 50 kGy mempunyai darjah pengembungan yang lebih tinggi secara signifikan (p<0.0001) dalam metanol (619%) berbanding air suling (510%) pada suhu bilik selepas 24 jam. Kekuatan ionik persekitaran mempengaruhi dengan peningkatan kepekatan natrium klorida menurunkan darjah pengembungan. Hidrogel juga peka terhadap perubahan pH: pengembungan meningkat dengan peningkatan pH dan nilai optimal dicapai pada pH 7. Selain itu pengembungan juga meningkat dengan peningkatan suhu dari 25°C sehingga 50°C. Kesimpulannya, keupayaan hidrogel selulosa bakteria-asid akrilik dedahan irradiasi elektron bertindak balas terhadap pelbagai rangsangan faktor persekitaran, menjadikan ia satu bahan yang boleh dibangunkan sebagai sistem penyampaian aktif untuk dadah, protein dan hormon.
Nata de coco, a dessert originally from the Philippines is produced by fermentation of coconut water with a culture of Acetobacter xylinum, a gram negative bacterium. Acetobacter xylinum metabolizes glucose in coconut juice and converts it into bacterial cellulose that has unique properties including high purity, crystallinity and mechanical strength. Because the main component of nata de coco is bacterial cellulose, nata de coco was purified, extracted and characterized to determine whether pure cellulose could be isolated from it. The FTIR spectra of bacterial cellulose from nata de coco showed distinguish peaks of 3440 cm-1, 2926 cm-1, 1300 cm-1, 1440 cm-1, 1163 cm-1 and 1040 cm-1, which correspond to O-H stretching, C-H stretching, C-H bending, CH2 bending, C-O-C stretching and C-O stretching, respectively, and represent the fingerprints of pure cellulose component. Moreover, the FTIR curve showed a pattern similar to other bacterial cellulose spectra reported by report. Thermal analysis showed a DTG peak at 342°C, which falls in the range of cellulose degradation peaks (330°C - 370°C). On the other hand, the TGA curve showed 1 step of degradation, and this finding confirmed the purity of nata de coco. Bacterial cellulose powder produced from nata de coco was found to be soluble only in cupriethylenediamine, a well known solvent for cellulose; thus, it was confirmed that nata de coco is a good source of bacterial cellulose. The purity of bacterial cellulose produced from nata de coco renders it suitable for research that uses pure cellulose.
Background: Sewage workers have a higher risk of exposure to various potential occupational respiratory hazards found in sewage plants. Although previous studies discuss occupational respiratory hazard concentration impacting sewage workers' respiratory health, the results are scarce and mixed. Hence, there is a need to identify the potential respiratory hazards in sewage plants so as to clarify the short- and long-term respiratory health effects. Therefore, this systematic review (SR) aims to critically review previous studies investigating potential respiratory hazards found at sewage plants and their effects on sewage workers' respiratory health. Methods: An SR was conducted using PubMed, EBSCO Medline, Web of Science, Scopus, and Google Scholar on peer-reviewed studies published between January 1994 and October 2020 evaluating the impact of potential exposure to respiratory hazards and its effects on respiratory health among sewage workers. "Sewage treatment plant," "respiratory hazards," and "respiratory health effects" were the three main search terms chosen in this SR. The inclusion criteria were (1) studies on potential occupational respiratory hazard exposure among sewage workers, (2) manuscripts written in English, and (3) studies published in the peer-reviewed literature. The human observational studies' quality was assessed using the Effective Public Health Practice Project Quality Assessment Tool. Results: We identified 5,660 articles through an initial database search. Only 26 items met the inclusion criteria and were included in this review; 15 human observational studies and 11 environmental assessment studies were conducted in the sewage industries. Most of the human observational studies were rated as moderate quality, two studies were rated as weak quality, and one study with strong quality was identified. Hydrogen sulfide, bioaerosols, particulate matter 2.5 (PM 2.5), and volatile organic compounds (VOC) were found to be potential respiratory hazards. Most of the risks contributed to adverse outcomes on the sewage workers' respiratory health with some inconsistent findings on the relationship between respiratory hazard exposure and respiratory health effects. Conclusion: Our review finds that, although this area is of great importance, quality studies are still lacking. There is a need for additional studies to clarify the effects of respiratory hazard exposure on sewage workers and respiratory health, especially PM 2.5 and VOC.
This study aimed to identify the Acanthamoeba genotypes and their pathogenic potential in five recreational hot springs in Peninsular Malaysia. Fifty water samples were collected between April and September 2018. Physical parameters of water quality were measured in situ while chemical and microbiological analyses were performed in the laboratory. All samples were filtered through the nitrocellulose membrane and tested for Acanthamoeba using both cultivation and polymerase chain reaction (PCR) by targeting the 18S ribosomal RNA gene. The pathogenic potential of all positive isolates was identified using thermo- and osmotolerance tests. Thirty-eight (76.0%) samples were positive for Acanthamoeba. Water temperature (P = 0.035), chemical oxygen demand (P = 0.026), sulphate (P = 0.002) and Escherichia coli (P < 0.001) were found to be significantly correlated with the presence of Acanthamoeba. Phylogenetic analysis revealed that 24 samples belonged to genotype T4, nine (T15), two (T3) and one from each genotype T5, T11 and T17. Thermo- and osmotolerance tests showed that 6 (15.79%) of the Acanthamoeba strains were highly pathogenic. The existence of Acanthamoeba in recreational hot springs should be considered as a health threat among the public especially for high-risk people. Periodic surveillance of hot spring waters and posting warning signs by health authorities is recommended to prevent disease related to pathogenic Acanthamoeba.
The purpose of this study was to produce a novel pH sensitive hydrogel with superior thermal stability, composed of
poly(acrylic acid) (PAA) and cellulose nanocrystal (CNC). CNC was extracted from kenaf fiber through a series of alkali
and bleaching treatments followed by acid hydrolysis. PAA was then subjected to chemical cross-linking using the crosslinking
agent (N,N-methylenebisacrylamide) in CNC suspension. The mixture was casted onto petri dish to obtain disc
shape hydrogel. PAA/cellulose hydrogel with the same composition ratio were also prepared as control. The effect of
reaction conditions such as the ratio of PAA and CNC on the swelling behavior of the hydrogel obtained towards pH
was studied. The obtained hydrogel was further subjected to different tests such as thermogravimetric analysis (TGA) to
study the thermal behavior, Fourier transform infrared for functional group identification and swelling test for swelling
behavior at different pH. The cross-linking of PAA was verified with FTIR with the absence of C=C double bond. In TGA
test, PAA/CNC hydrogel showed significantly higher thermal stability compared with pure PAA hydrogel. The hydrogel
obtained showed excellent pH sensitivity and experienced maximum swelling at pH7. The PAA/CNC hydrogel can be
developed further as drug carrier
In order to determine the safety level of water parameters and nutrients in the natural environment of fish and freshwater prawn in Nyatuh River, Terengganu, Malaysia, it is necessary to conduct an assessment of water quality parameters. Due to its important, a study was conducted to assess the water quality parameter and nutrients contents from Nyatuh River of Setiu Terengganu in relations to the population of freshwater prawn, Macrobrachium rosenbergii caught along the Nyatuh River basin. Total of four expeditions and five stations at different tidal condition for the water quality parameter were assessed during the study. From the results achieved, the overall temperature varied between (26.56°C-29.30°C), dissolved oxygen, DO (3.59 mg/L-6.50 mg/L), pH (4.99-7.01), salinity (0.01ppt-4.22ppt), depth (2.71 m-5.54 m) while for ammonia (0.01 mg/L-0.24 mg/L), nitrite (0.01 mg/L-0.05 mg/L) and phosphate (0.01 mg/L-0.12 mg/L). While the number of prawns caught are 176, 160, 102 and 68 for Expeditions 1, 2, 4 and 3, respectively. Possibly, the heterogeneous number of prawns caught is a result of significant differences in water level depth during high tides and low tides, as well as a fluctuation in the ammonia concentration levels in each of the stations and expeditions. For statistical analysis, the temperature showed no significant difference between the expedition, stations and tidal. That is p = 0.280, p > 0.05 and F = 1.206, respectively. While dissolved oxygen, DO, showed no significant difference as well, that is p = 0.714, p > 0.05 and F = 0.737. However, the level of water depth was significantly different between expedition, station and tidal, that is p = 0.000, p < 0.05 and F = 3.120. Ammonia, on the other hand shows no significant difference between expedition, station and tidal, that is p = 0.476, p > 0.05 and F = 0.973. The same goes for nitrite and phosphate concentration. There was no significant difference between expedition, stations and tidal, that is p = 0.569, p > 0.05 and F = 0.879 and p = 0.247, p > 0.05, F = 1.255, respectively. In Expedition 1, the good water quality parameter and very low ammonia concentration resulted in a larger prawn population as compared to other expeditions. The distribution or mixture of prawns caught is heterogeneous at different stations due to the significant differences in water depth and also to the fluctuation in water quality due to varying ammonia levels. In conclusion, the water quality in Nyatuh River fluctuated across expeditions, stations, and tides, as well as significant differences in water level depths between high and low tides. Due to the rapid growth and importance of industrial and aquaculture operations along the river, extra attention should be devoted to avoid the impact of excessive pollutant in order to protect the ecosystem.
Blends of fibre-reinforced rubber based on natural rubber-thermoplastic (NR/LLDPE) reinforced by aramid fibre have been done using melt blending process. Two different processing methods were used; internal mixer and extrusion compounding in twin screw extruder. Twaron loading in the system was varied from 0 to 30%. It was found that increasing the amount of aramid fibre led to an increase in the tensile strength, tensile modulus and hardness of the composites while the strain decreased rapidly. The results showed that the optimum composition of filler loading in NR/LLDPE blend is 20%. The ,echanical behaviour was caused by the strong Twaron-matrices interaction in the composites and effective stress concentrating function of Twaron. Composites prepared using the twin-screw extruder have a higher tensile strength and tensile using the twin-screw extruder have a higher tensile stength and tensile modulus but lower impact strength compared to those prepared using internal mixer. Study of the fracture surface by scanning electron microscopy showed that the composite prepared using the internal mixer produced random fiber orientation while the twin-screw extruder produced the fibers aligned to the longitudinal direction. The results indicate that the mechanical properties of the composite were significantly influenced by the processing technique.
Penyediaan komposit getah asli termoplastik daripada NR/LLDPE yang diperkuat gentian Twaron telah dijalankan melalui proses adunan leburan. Dua kaedah penyediaan yang berbeza digunakan iaitu menggunakan mesin pencampur dalaman manakala kaedah kedua menggunakan pengekstrud skru kembar. Kandungan Twaron di dalam komposit telah diubah daripada 0 hingga 30%. Keputusan menunjukkan bahawa penambahan Twaron telah meningkatkan nilai tegasan maksima, modulus Young dan kekuatan hentaman komposit tetapi menurunkan nilai terikan maksima. Kandungan Twaron yang optimum adalah 20%. Kehadiran Twaron telah membentuk satu jaringan saling tindak gentian-matriks menyebabkan kekuatan regangan komposit meningkat. Twaron juga berfungsi sebagai penyerap hentaman yang berkesan. Penyediaan komposit menggunakan pengekstrud skru berkembar telah menghasilkan nilai kekuatan regangan yang lebih tinggi berbanding penggunaan pencampur dalaman sebaliknya kekuatan hentaman yang lebih rendah. Kajian morfologi menggunakan mikroskop imbasan elektron mendapati komposit yang disediakan menggunakan pencampur dalaman menghasilkan gentian dengan orientasi rawak manakala pengekstrud skru kembar menghasilkan orientasi gentian yang selari. Keputusan ini menunjukkan bahawa sifat mekanik komposit NR/LLDPE yang diperkuat Twaron sangat dipengaruhi oleh teknik pemprosesan.
Kesan penambahan pengisi sekam padi dan tanah liat ke dalam matriks getah asli getah asli cecair polietilena berketumpatan tinggi (NR/LNR/HDPE), NR/HDPE dan HDPE terhadap sifat mekanik dan morfologi adunan telah dikaji. Pemprosesan adunan dilakukan pada suhu 140°C dan kadar percampuran 50 r.p.m. selama 16 minit. Pra-pemanasan pengisi selama 4 minit pada suhu 80°C dilakukan sebelum pengadunan dengan matriks bagi meminimumkan kesan lembapan. Getah asli cecair digunakan sebagai agen pengserasi dalam adunan komposit. Pengisian sekam padi (SP) dan tanah liat (TL) dalam matrik HDPE, NR/HDPE serta NR/LNR/HDPE umumnya menurunkan nilai kekuatan tensil dan kekuatan hentaman tetapi meningkatkan nilai modulus. Kehomogenan adunan komposit berpengisi yang dikenal pasti melalui pemeriksaan morfologi menggunakan mikroskop imbasan elektron (SEM) menunjukkan masalah aglomerasi dan interaksi antara muka dalam komposit berlaku. Kelikatan leburan dan interaksi antara bahan menentukan arah pergerakan serta serakan pengisi dalam komposit. Daripada keputusan yang diperolehi dan merujuk kedua-dua sifat pengisi, SP adalah lebih serasi dengan NR disebabkan potensi interaksi antara kumpulan berfungsi permukaan pengisi selulosa (SP) seperti –OH dengan ikatan ganda dua NR berbanding TL. Ciri fizik permukaan TL yang kurang bersifat hidrofilik berbanding SP pula menyebabkan TL lebih cenderung berinteraksi dan tersebar dengan baik dalam HDPE.
Blends of fiber-reinforced rubber (FRR) based on natural rubber-thermoplastic (NR/LLDPE) and epoxidized natural rubber Âthermoplastic (ENR/LLDPE) reinforced by aramid fibre have been done using melt blending process. Twaron aramid fibres (Teijin-Twaron) used in this project were treated with epoxy adhesion activated and resorcinol formaldehyde latex (RFL). It was found that with increasing amount of aramid fibre led to increase the maximum stress, tensile modulus, impact strength and hardness of the composites while the strain at break decreased rapidly. The results show that the optimum composition of filler loading in NR/LLDPE blend is 20%. However, in the case of the ENR/LLDPE composite, the tensile strength and modulus increase with increasing amount of the fibre above 20%. The results indicate that the interfacial adhesion between ENR/LLDPE and aramid is better than for the NR/LLDPE.
[Penyediaan adunan getah asli termoplastik dan getah asli terepoksida termoplastik yang diperkuat dengan gentian aramid telah dilakukan melalui proses adunan leburan. Gentian aramid yang digunakan adalah gentian pendek Twaron (Teijin-Twaron) yang dirawat dengan bahan pelekat epoksi dan resorcinolformaldehid latex (RFL). Hasil yang diperolehi menunjukkan bahawa kesan penambahan gentian aramid telah meningkatkan tegasan maksima, modulus regangan, kekuatan hentaman dan kekerasan kedua-dua adunan tersebut tetapi menurunkan nilai terikan pada takat putus. Bagi adunan NR/LLDPE didapati komposisi gentian yang paling optima adalah pada 20%. Penambahan gentian aramid seterusnya hanya menurunkan sifat mekanik adunan. Sebaliknya bagi adunan ENR/LLDPE, didapati komposisi gentian melebihi 20% masih menunjukkan peningkatan tegasan maksima dan modulus regangan. Keputusan ini menunjukkan bahawa interaksi antaramuka gentian aramid dan matriks dalam adunan ENR/LLDPE lebih baik berbanding NR/LLDPE].
In this work, the feasibility of coagulation-flocculation coupled with UV-based sulfate radical oxidation process (UV/SRAOP) in the removal of chemical oxygen demand (COD) of stabilized landfill leachate (SLL) was evaluated. For coagulation-flocculation, ferric chloride (FeCl3) was used as the coagulant. The effect of initial pH of SLL and COD:FeCl3 ratio on the COD removal was evaluated. The result revealed that COD:FeCl3 ratio of 1:1.3 effectively removed 76.9% of COD at pH 6. The pre-treated SLL was then subjected to UV/SRAOP treatment. For UV/SRAOP, the sulfate radical (SR) was generated using UV-activated persulfate (UV/PS) and peroxymonosulfate (UV/PMS). The dosage of oxidant and reaction time were found to be the main parameters that influence the efficiency of COD removal. On the other hand, the effect of initial pH (3-7) and the type of oxidant (PS and PMS) was found to have no significant influence on COD removal efficiency. At optimum conditions, approximately 90.9 and 91.5% of COD was successfully removed by coagulation-flocculation coupled with UV/PS and UV/PMS system, respectively. Ecotoxicity study using zebrafish showed a reduction in toxicity of SLL from 10.1 to 1.74 toxicity unit (TU) after coagulation-flocculation. The TU remained unchanged after UV/PS treatment but slightly increased to 1.80 after UV/PMS treatment due to the presence of residual sulfate ion in the treated effluent. In general, it can be concluded that coagulation-flocculation coupled with UV/SRAOP could be a potential water treatment method for SLL treatment.
The treatment of stabilized landfill leachate (SLL) by conventional biological treatment is often inefficient due to the presence of bio-recalcitrant substances. In this study, the feasibility of coagulation-flocculation coupled with the Fenton reaction in the treatment of SLL was evaluated. The efficiency of the selected treatment methods was evaluated through total organic carbon (TOC) removal from SLL. With ferric chloride as the coagulant, coagulation-flocculation was found to achieve the highest TOC removal of 71% at pH 6. Then, the pretreated SLL was subjected to the Fenton reaction. Nearly 50% of TOC removal was achieved when the reaction was carried out at pH 3, H2O2:Fe2+ ratio of 20:1, H2O2 dosage of 240 mM and 1 h of reaction time. By coupling the coagulation-flocculation with the Fenton reaction, the removal of TOC, COD (chemical oxygen demand) and turbidity of SLL were 85%, 84% and 100%, respectively. The ecotoxicity study performed using zebrafish revealed that 96 h LC50 for raw SLL was 1.40% (v/v). After coagulation-flocculation, the LC50 of the pretreated SLL was increased to 25.44%. However, after the Fenton reaction, the LC50 of the treated SLL was found to decrease to 10.96% due to the presence of H2O2 residue. In this study, H2O2 residue was removed using powdered activated charcoal. This method increased the LC50 of treated effluent to 34.48% and the removal of TOC and COD was further increased to 90%. This finding demonstrated that the combination of the selected treatment methods can be an efficient treatment method for SLL.
Indoor air quality (IAQ) has recently gained substantial traction as the airborne transmission of infectious respiratory disease becomes an increasing public health concern. Hospital indoor environments are complex ecosystems and strategies to improve hospital IAQ require greater appreciation of its potentially modifiable determinants, evidence of which are currently limited. This mini-review updates and integrates findings of previous literature to outline the current scientific evidence on the relationship between hospital IAQ and building design, building operation, and occupant-related factors. Emerging evidence has linked aspects of building design (dimensional, ventilation, and building envelope designs, construction and finishing materials, furnishing), building operation (ventilation operation and maintenance, hygiene maintenance, access control for hospital users), and occupants' characteristics (occupant activities, medical activities, adaptive behavior) to hospital IAQ. Despite the growing pool of IAQ literature, some important areas within hospitals (outpatient departments) and several key IAQ elements (dimensional aspects, room configurations, building materials, ventilation practices, adaptive behavior) remain understudied. Ventilation for hospitals continues to be challenging, as elevated levels of carbon monoxide, bioaerosols, and chemical compounds persist in indoor air despite having mechanical ventilation systems in place. To curb this public health issue, policy makers should champion implementing hospital IAQ surveillance system for all areas of the hospital building, applying interdisciplinary knowledge during the hospital design, construction and operation phase, and training of hospital staff with regards to operation, maintenance, and building control manipulation. Multipronged strategies targeting these important determinants are believed to be a viable strategy for the future control and improvement of hospital IAQ.