Fly ash is the finely divided mineral residue resulting from the combustion of coal in electric generating plants. Fly ash consists of inorganic, incombustible matter present in the coal that has been fused during combustion into a glassy, amorphous structure. Fly ash particles are generally spherical in shape and range in size from 2 μm to 10 μm. They consist mostly of silicon dioxide (SiO2), aluminium oxide (Al2O3) and iron oxide (Fe2O3). Fly ash like soil contains trace concentrations of the following heavy metals: nickel, vanadium, cadmium, barium, chromium, copper, molybdenum, zinc and lead. The chemical compositions of the sample have been examined and the fly ash are of ASTM C618 Class F.
The existence of surface organic capping ligands on quantum dots (QDs) has limited the potential in QDs emission properties and energy band gap structure alteration as well as the carrier localization. This drawback can be addressed via depositing a thin layer of a semiconductor material on the surface of QDs. Herein, we report on the comparative study for photoluminescent (PL) properties of PbS and PbS/MnS QDs. The carrier localization effect due to the alteration of energy band gap structure and carrier recombination mechanism in the QDs were investigated via PL measurements in a temperature range of 10-300 K with the variation of the excitation power from 10 to 200 mW. For PbS QDs, the gradient of integrated PL intensity (IPL) as a function of excitation power density graph was less than unity. When the MnS shell layer was deposited onto the PbS core, the PL emission exhibited a blue shift, showing dominant carrier recombination. It was also found that the full width half-maximum showed a gradual broadening with the increasing temperature, affirming the electron-phonon interaction.
Penyelidikan ini mengkaji tingkah laku cadmium (Cd) melalui tanah baki granit yang dipadatkan. Sampel tanah baki granit telah diambil di kawasan Broga, Selangor dan dikaji menggunakan tiga kaedah ujian utama iaitu; ujian fizikal (taburan saiz butiran, had-had Atterberg, graviti tentu, pemadatan dan kebolehtelapan), ujian kimia (pH, bahan organik, luas permukaan spesifik (SSA) dan kadar pertukaran kation (CEC) serta ujian mini kolum turasan. Melalui ujian kolum turasan, konsep kebolehtelapan turus menurun digunakan yang melibatkan tiga faktor iaitu halaju/daya-G, ketebalan sampel dan jenis larutan yang digunakan. Graf lengkung bulus menunjukkan kepekatan Cd dalam tanah baki granit semakin meningkat dengan peningkatan halaju. Urutan kapasiti penjerapan semakin meningkat terhadap kadar putaran alat emparan/daya tarikan graviti (G); 230G>520G>920G>1440G. Pergerakan logam berat melalui tanah baki juga meningkat dengan peningkatan halaju/daya-G. Lengkung bulus juga menunjukkan pergerakan Cd secara songsang dengan ketebalan lapisan tanah di dalam kolum. Masa penembusan bagi ketebalan 20 mm juga lebih lama berbanding ketebalan 15 dan 10 mm. Manakala jumlah Cd yang terjerap oleh tanah baki granit dalam larutan campuran adalah rendah berbanding larutan tunggal (masa yang singkat untuk menembusi lengkung bulus). Tanah baki granit juga mempunyai kapasiti penampanan yang rendah (pHfinal = 4 - 7). Kajian ini menunjukkan bahawa pencirian fiziko-kimia dan sifat penjerapan tanah dengan menggunakan ujian mini kolum turasan mempunyai kaitan yang kuat untuk mencirikan tanah baki granit untuk dijadikan pelapik lempung tereka bentuk.
Various amendments are used to reduce the phytoavailability of heavy metals in contaminated soils, but recently the use of biochar is receiving serious attention. In this study, two particle sizes of an oil palm empty fruit bunch biochar (EFBB); <50 µm (F-EFBB) and >2 mm (C-EFBB) were applied at either 0, 0.5, or 1% (w/w) to soils contaminated with either Cd or Pb and the phytoavailability of these metals by mustard plants grown on the soils was evaluated. Results revealed that the application of EFBB at 1% significantly increased plant growth parameters as compared with the control in Cd-soil. However, there was no significant effect of EFBB application rate on plant growth parameters in Pb-soil. There was a significant difference in the concentrations of Cd and Pb in the plant root and shoot between soils receiving different particle sizes of EFBB. The treatment of 1% F-EFBB gave the lowest concentration of the Cd concentration in the shoot (115.200 mgkg-1) and Pb concentration in the root and shoot (4196.000 and 78.467 mgkg-1, respectively) as compared with the other treatments. Therefore, F-EFBB application at high rates can be recommended for reducing the phytoavailability of Cd and Pb in contaminated soils.
Eukaryotic cells typically respond to stress conditions by inhibiting global protein synthesis. The initiation phase is the main target of regulation and represents a key control point for eukaryotic gene expression. In Saccharomyces cerevisiae and mammalian cells this is achieved by phosphorylation of eukaryotic initiation factor 2 (eIF2α). We have examined how the fungal pathogen Candida albicans responds to oxidative stress conditions and show that oxidants including hydrogen peroxide, the heavy metal cadmium and the thiol oxidant diamide inhibit translation initiation. The inhibition in response to hydrogen peroxide and cadmium largely depends on phosphorylation of eIF2α since minimal inhibition is observed in a gcn2 mutant. In contrast, translation initiation is inhibited in a Gcn2-independent manner in response to diamide. Our data indicate that all three oxidants inhibit growth of C. albicans in a dose-dependent manner, however, loss of GCN2 does not improve growth in the presence of hydrogen peroxide or cadmium. Examination of translational activity indicates that these oxidants inhibit translation at a post-initiation phase which may account for the growth inhibition in a gcn2 mutant. As well as inhibiting global translation initiation, phosphorylation of eIF2α also enhances expression of the GCN4 mRNA in yeast via a well-known translational control mechanism. We show that C. albicans GCN4 is similarly induced in response to oxidative stress conditions and Gcn4 is specifically required for hydrogen peroxide tolerance. Thus, the response of C. albicans to oxidative stress is mediated by oxidant-specific regulation of translation initiation and we discuss our findings in comparison to other eukaryotes including the yeast S. cerevisiae.
Pollutants, especially heavy metals like cadmium, Chromium, lead and mercury, play a significant role in causing various water-borne diseases to humans. This study evaluates the sorption properties of bioactive constituents of Moringa oleifera seeds for decontamination of cadmium at laboratory scale. The performance of the bioactive constituent extracted by salt extraction method was enhanced by process optimization with various concentration of bioactive dosages, agitation speed, contact time, pH and heavy metal concentrations. Statistical optimization was carried out for evaluating the polynomial regression model through effect of linear, quadratic and interaction of the factors. The maximum removal of cadmium was 72% by using 0.2 g/l of bioactive dosage.
This study investigates the separation of two heavy metals, Cd(II) and Cu(II), from the mixed synthetic feed using a liquid-liquid extraction. The current study uses tri-octyl methylammonium chloride (Aliquat 336) as the extractant (with tributyl phosphate (TBP) as a phase modifier), diluted in toluene, in order to investigate the selective extraction of Cd(II) over Cu(II) ions. We investigate the use of ethylenediaminetetraacetic acid (EDTA) as a masking agent for Cu(II), when added in aqueous feed, for the selective extraction of Cd(II). Five factors that influence the selective extraction of Cd(II) over Cu(II) (the equilibrium pH (pHeq), Aliquat 336 concentration (Aliquat 336), TBP concentration (TBP), EDTA concentration (EDTA), and organic to aqueous ratio (O:A)) were analyzed. Results from a 25-1 fractional factorial design show that Aliquat 336 significantly influenced Cd(II) extraction, whereas EDTA was statistically significant for the antagonistic effect on the E% of Cu(II) in the same system. Moreover, results from optimization experiment showed that the optimum conditions are Aliquat 336 concentration of 99.64 mM and EDTA concentration of 48.86 mM-where 95.89% of Cd(II) was extracted with the least extracted Cu(II) of 0.59%. A second-order model was fitted for optimization of Cd(II) extraction with a R2 value of 0.998, and ANOVA results revealed that the model adequately fitted the data at a 5% significance level. Interaction between Aliquat 336 and Cd(II) has been proven via FTIR qualitative analysis, whereas the addition of TBP does not affect the extraction mechanism.
This study aims to optimise the operating conditions for the supercritical fluid extraction (SFE) of toxic elements from fish oil. The SFE operating parameters of pressure, temperature, CO2 flow rate and extraction time were optimised using a central composite design (CCD) of response surface methodology (RSM). High coefficients of determination (R²) (0.897-0.988) for the predicted response surface models confirmed a satisfactory adjustment of the polynomial regression models with the operation conditions. The results showed that the linear and quadratic terms of pressure and temperature were the most significant (p < 0.05) variables affecting the overall responses. The optimum conditions for the simultaneous elimination of toxic elements comprised a pressure of 61 MPa, a temperature of 39.8ºC, a CO₂ flow rate of 3.7 ml min⁻¹ and an extraction time of 4 h. These optimised SFE conditions were able to produce fish oil with the contents of lead, cadmium, arsenic and mercury reduced by up to 98.3%, 96.1%, 94.9% and 93.7%, respectively. The fish oil extracted under the optimised SFE operating conditions was of good quality in terms of its fatty acid constituents.
A three layer waveguiding silicon dioxide (SiO(2))/silicon nitride (Si(3)N(4))/SiO(2) structure on silicon substrate was proposed as an optically efficient biosensor for calibration of heavy metal ions in drinking water. The catalytic activities of urease and acetylcholine esterase (AchE) were inhibited by the presence of cadmium (Cd(2+)) and lead (Pb(2+)) ions. The detection limit as low as 1 ppb was achieved by employing the technique of total reflection at the interface between the Si(3)N(4) core and composite polyelectrolyte self-assembled (PESA) membranes containing cyclotetrachromotropylene (CTCT) as an indicator.
A flow injection (FI) method with on-line preconcentration using a mini-column loaded with 8-hydroxyquinoline immobilized on controlled pore glass (CPG-8HQ) is described for the determination of trace metals by ion chromatography (IC) with pyridine-2-6-dicarboxylic acid (PDCA) as the eluent. Copper, cadmium, lead, zinc, nickel and iron were determined at ppb level after post-column derivatization with 4-(2-pyridylazo)-resorcinol (PAR). The detection limits (3sigma) for the FI/IC system were 8.27, 0.89, 0.09, 0.06, 0.09 and 0.07 g l(-1) for Pb(2+), Cd(2+), Cu(2+) Ni(2+), Zn(2+) and Fe(3+), respectively, using 5 ml sample volume. The method was applied to the analysis of Malaysian natural waters.
With the population growth, urbanization and industrialization, China has become a hotspot of atmospheric deposition nitrogen (ADN), which is a threat to ecosystem and food safety. However, the impacts of increased ADN on rice growth and grain metal content are little studied. Based on previous long-term ADN studies, greenhouse experiment was conducted with four simulated ADN rates of 0, 30, 60 and 90 kg N ha-1 yr-1 (CK, N1, N2 and N3 as δ15N, respectively) to assess rice growth and metal uptake in a red soil ecosystem of southeast China during 2016-2017. Results showed that simulated ADN could promote rice growth and increase yields by 15.68-24.41% (except N2) and accumulations of cadmium (Cd) or copper (Cu) in organs. However, there was no linear relationship between ADN rate and rice growth or Cd or Cu uptake. The 15N-ADN was mainly accumulated in roots (21.31-67.86%) and grains (25.26-49.35%), while Cd and Cu were primarily accumulated in roots (78.86-93.44% and 90.00-96.24%, respectively). 15N-ADN and Cd accumulations in roots were significantly different between the two growing seasons (p
Biochar can be used for soil remediation in environmentally beneficial manner, especially when combined with nanomaterials. After a decade of research, still, no comprehensive review was conducted on the effectiveness of biochar-based nanocomposites in controlling heavy metal immobilization at soil interfaces. In this paper, the recent progress in immobilizing heavy metals using biochar-based nanocomposite materials were reviewed and compared their efficacy against that of biochar alone. In details, an overview of results on the immobilization of Pb, Cd, Cu, Zn, Cr, and As was presented by different nanocomposites made by various biochars derived from kenaf bar, green tea, residual bark, cornstalk, wheat straw, sawdust, palm fiber, and bagasse. Biochar nanocomposite was found to be most effective when combined with metallic nanoparticles (Fe3O4 and FeS) and carbonaceous nanomaterials (graphene oxide and chitosan). This study also devoted special consideration to different remediation mechanisms by which the nanomaterials affect the effectiveness of the immobilization process. The effects of nanocomposites on soil characteristics related to pollution migration, phytotoxicity, and soil microbial composition were assessed. A future perspective on nanocomposites' use in contaminated soils was presented.
The present work was aimed at evaluating the multi-metals column adsorption of lead(II), cadmium(II) and manganese(II) ions onto natural bentonite. The bentonite clay adsorbent was characterized for physical and chemical properties using X-ray diffraction, X-ray fluorescence, Brunauer-Emmett-Teller surface area and cation exchange capacity. The column performance was evaluated using adsorbent bed height of 5.0 cm, with varying influent concentrations (10 mg/L and 50 mg/L) and flow rates (1.4 mL/min and 2.4 mL/min). The result shows that the breakthrough time for all metal ions ranged from 50 to 480 minutes. The maximum adsorption capacity was obtained at initial concentration of 10 mg/L and flow rate of 1.4 mL/min, with 2.22 mg/g of lead(II), 1.71 mg/g of cadmium(II) and 0.37 mg/g of manganese(II). The order of metal ions removal by natural bentonite is lead(II) > cadmium(II) > manganese(II). The sorption performance and the dynamic behaviour of the column were predicted using Adams-Bohart, Thomas, and Yoon-Nelson models. The linear regression analysis demonstrated that the Thomas and Yoon-Nelson models fitted well with the column adsorption data for all metal ions. The natural bentonite was effective for the treatment of wastewater laden with multi-metals, and the process parameters obtained from this work can be used at the industrial scale.
A widely distributed urban bird, the house crow (Corvus splendens), was used to assess bioavailable heavy metals in urban and rural environments across Pakistan. Bioaccumulation of arsenic (As), zinc (Zn), lead (Pb), cadmium (Cd), nickel (Ni), iron (Fe), manganese (Mn), chromium (Cr), and copper (Cu) was investigated in wing feathers of 96 crows collected from eight locations and categorized into four groups pertaining to their geographical and environmental similarities. Results revealed that the concentrations of Pb, Ni, Mn, Cu, and Cr were positively correlated and varied significantly among the four groups. Zn, Fe, Cr, and Cu regarded as industrial outputs, were observed in birds both in industrialized cities and in adjoining rural agricultural areas irrigated through the Indus Basin Irrigation System. Birds in both urban regions accrued Pb more than the metal toxicity thresholds for birds. The house crow was ranked in the middle on the metal accumulation levels in feathers between highly accumulating raptor and piscivore and less contaminated insectivore and granivore species in the studied areas,. This study suggests that the house crow is an efficient bioindicator and supports the feasibility of using feathers to discriminate the local pollution differences among terrestrial environments having different levels and kinds of anthropogenic activities.
Tiger’s Milk mushroom has been used for medicinal purposes by local aborigines to treat asthma, breast cancer, cough, fever and food poisoning. Molecular phylogenetic analysis utilizing RNA polymerase II, second largest subunit (RPB2) gene, identified the wild Tiger’s Milk mushrooms collected from the state of Pahang in Malaysia for this study as Lignosus rhinocerus in the order Polyporales. The tuber, stipe and pileus of this mushroom were analyzed for their basic nutritional composition (fat, protein, and carbohydrate) and toxic metal content profile (Cadmium, Lead and Mercury). The moisture content of these mushroom parts varied from 32.22% (pileus) – 46.31% (stipe). The dry matter of the mushrooms contained 2.76% (stipe) – 6.60% (pileus) proteins, 0.21% (pileus) – 0.30% (tuber) fat, 1.76% (stipe) – 4.38% (tuber) ash and 38.47% (stipe) – 56.30% (pileus) carbohydrates. The toxic metal content of the mushroom samples ranged from 0.03–0.12 mg/kg for Cd, 0.80–1.94 mg/kg for Pb and 0.05–0.10 mg/kg for Hg. The present study demonstrated that L. rhinocerus is a potential source of food due to its high carbohydrate content. In addition, the trace levels of toxic metals in this mushroom are within the safe level for consumption.
A series of batch laboratory studies were conducted to investigate the suitability of activated carbon SA2 for the removal of cadmium ions and zinc ions from their aqueous solutions. The single component equilibrium data were analyzed using the Langmuir and Freundlich isotherms. Overall, the Langmuir isotherm showed a better fitting for all adsorptions under investigation in terms of correlation coefficient and error analysis (SSE only 18.2 for Cd2+ and 47.95 for Zn2+). As the binary adsorption is competitive, extended Langmuir models could not predict the binary component isotherm well. The modified extended Langmuir models were used to fit the binary system equilibrium data. The binary isotherm data could be described reasonably well by the modified
extended Langmuir model, as indicated in the error analysis.
A study was conducted to quantitate the concentrations of heavy metals, such as Hg, Pb and Cd in eight species of marine fin fish caught off the coast of Langkawi Island in Malaysia, as well as in its waters. The same fish were also used to determine the content of nutritional minerals, such as copper (Cu), zinc (Zn), calcium (Ca), and manganese (Mn).Fish and water samples were collected from four different areas, namely (1) Main Jetty Pulau Tuba (MJPT), (2) Teluk Cempedak Jetty (TCJ), (3) Simpang Tiga Chian Lian (STCL) and (4) Main Jetty Kuah (MJK) around Langkawi Island. Results showed that for the vital elements, all species had higher concentration of Zn compared to other elements. For the toxic elements, lead (Pb) and mercury (Hg) were found to have lower concentration of the mean values than the permissible limits set by FAO/WHO (1984). However, cadmium (Cd) level was slightly higher than the permissible limit but was still acceptable according to the Malaysian Food Regulation (1985). It can be concluded that all fish species studied are safe to be consumed.
In this article, an easy and quick method based on microwave assisted acid digestion technique prior to quantification using inductively coupled plasma mass spectrometry for the analysis of heavy metals in cocoa beans, cocoa powder and chocolate was established and validated for arsenic (As), cadmium (Cd), lead (Pb), and antimony (Sb). Limit of quantification for all elements were product dependent and varies from 7.84 to 194.52 µg/kg. The recoveries of the heavy metals at 250 and 1000 µg/kg spiking levels were ranged between 96.27-108.75%, 90.43-101.97% and 89.72-106.26% for cocoa beans, cocoa powder, and chocolate, respectively. Relative standard deviation values obtained were all below 20% and the expanded uncertainty measurements for the elements were less than 25%. The analysis of real samples found that the concentration level is far from the national alarming level except for cadmium in cocoa beans.
Rice is a predominant staple food in many countries. It is a great source of energy but can also accumulate toxic and trace metal(loid)s from the environment and pose serious health hazards to consumers if overdosed. This study aims to determine the concentration of toxic metal(loid)s [arsenic (As), cadmium (Cd), nickel (Ni)] and essential metal(loid)s [iron (Fe), selenium (Se), copper (Cu), chromium (Cr), cobalt (Co)] in various types of commercially available rice (basmati, glutinous, brown, local whites, and fragrant rice) in Malaysia, and to assess the potential human health risk. Rice samples were digested following the USEPA 3050B acid digestion method and the concentrations of metal(loid)s were analyzed using an inductively coupled plasma mass spectrometry (ICP-MS). Mean concentrations (mg/kg as dry weight) of metal(loid)s (n=45) across all rice types were found in the order of Fe (41.37)>Cu (6.51)>Cr (1.91)>Ni (0.38)>As (0.35)>Se (0.07)>Cd (0.03)>Co (0.02). Thirty-three percent and none of the rice samples surpassed, respectively, the FAO/WHO recommended limits of As and Cd. This study revealed that rice could be a primary exposure pathway to toxic metal(loid)s, leading to either noncarcinogenic or carcinogenic health problems. The non-carcinogenic health risk was mainly associated with As which contributed 63% to the hazard index followed by Cr (34%), Cd (2%), and Ni (1%). The carcinogenic risk to adults was high (>10-4) for As, Cr, Cd, and Ni. The cancer risk (CR) for each element was 5 to 8 times higher than the upper limit of cancer risk for an environmental carcinogen (<10-4). The findings from this study could provide the metal(loid)s pollution status of various types of rice which are beneficial to relevant authorities in addressing food safety and security-related issues.