1M NaOH Research Articles

Positive and negative aspects of suplhate-reducing bacteria in environment and industry

The submitted work is oriented on the study of two aspects of the sulphate-reducing bacteria metabolism: the metals bioprecipitation and the concrete biodeterioration. The bioprecipitation of metals with the bacterially produced hydrogen sulphide by sulphate-reducing bacteria (SRB) represents the positive effect of the SRB existence in the environment. It allows the industrial exploitation in the area of the removal metals from industrial wastewaters. Referred method involves principal stages such as: hydrogen sulphide bacterial production, metals precipitation by biologically produced hydrogen sulphide, metal sulphides separation, setting pH of the filtrate from previous steps by 1M NaOH and metal hydroxides separation. The basis of the first stage i.e. the hydrogen sulphide
 bacterial production is the cultivation of SRB. In the laboratory conditions the sodium lactate is the energetic substrate for the growth of bacteria. Its price is not economic for the application in the practice and is needed investigate the alternative substitutes. Therefore was studied the cultivation of sulphate-reducing bacteria to using the selected energetic substrates such as: calcium lactate, glycerol and whey. Experimental studies confirm that all chosen substrates are suitable alternative substrates of sodium lactate for the bacterial sulphate-reduction. In the regard to the efficiency of bacterial sulphate reduction the calcium lactate is the best. The biodeterioration of the concrete presents the negative effect of the SRB existence in the environment. The research was oriented on the simulation of the biodeterioration of concrete samples under the simultaneous influence of the sulphur-oxidising bacteria genera Acidithiobacillus thiooxidans and sulphatereducing bacteria genera Desulfovibrio in the environs of the waste water, the acid mine drainage, the nutrient medium and the distilled water. The observation of the surface structure changes of concrete samples confirms the highest biodeterioration influences in the case of the acid mine drainage application.

Lactic acid bacterial bacteriocins and their bioactive properties against food-associated antibiotic-resistant bacteria

PurposeIncidence of foodborne diseases and growing resistance of pathogens to classical antibiotics is a major concern in the food industry. Consequently, there is increasing demand for safe foods with fewer chemical additives but natural products which are not harmful to the consumers. Bacteriocins, produced by lactic acid bacteria (LAB), is of interest because they are active in a nanomolar range, do not have toxic effects, and are readily available in fermented food products.MethodsIn this research, LAB were isolated from fufu, gari, kunu, nono, and ogi using De Mann, Rogosa, and Sharpe agar. Cell-free supernatants were prepared from 18-24 h LAB culture grown on MRS broth. Effect of organic acid was eliminated by adjusting the pH of the supernatants to 7.0 with 1M NaOH while the effect of hydrogen peroxide was eliminated by treating with Catalase enzyme. The supernatant was then filter-sterilized using a membrane filtration unit with a 0.2-μm pore size millipore filter and subjected to agar well diffusion assay against foodborne antibiotic-resistant bacteria.ResultA total of 162 isolates were obtained from the food samples. The antimicrobial sensitivity test yielded positive results for 45 LAB isolates against Staphylococcus aureus ATCC 25923 while 52 LAB isolates inhibited Escherichia coli ATCC 25922. On confirmation of the bacteriocinogenic nature of the inhibitory substance, 4 of the LAB isolates displayed a remarkable degree of inhibition to Leuconostoc mesenteroides, Salmonella typhimurium, and Bacillus cereus. Agar well diffusion assay was also performed against antibiotic-resistant foodborne pathogens using the cell-free supernatant (CFS) obtained from Lactobacillus fermentum strain NBRC15885 (Limosilactobacillus fermentum), Lactobacillus fermentum strain CIP102980 (Limosilactobacillus fermentum), Lactobacillus plantarum strain JCM1149 (Lactiplantibacillus garii), and Lactobacillus natensis strain LP33 (Companilactobacillus nantensis). The foodborne pathogens exhibited a notable level of resistance to antibiotics, with B. cereus exhibiting a resistance profile of 40%, S. aureus (50%), K. pnuemoniae (70%), E. coli (60%), and S. typhi (40%). The (CFS) was able to inhibit the growth of B. cereus, Klebsiella pneumonia, S. typhimurium, S. aureus, and E. coli.ConclusionTherefore, it portends that the bacteriocins produced by the LAB isolated from these food products could act as probiotics for effective inhibition of the growth of antibiotic-resistant foodborne pathogens.

Contact angle of modified fibrovascular bundle of salacca (Salacca sumatrana Becc.) frond by NaOH+Na2SO3 combination

The fibrovascular bundle (FVB) of the salacca frond is one of the potential raw materials in the development of bio-composite technology. The purpose of this study was to investigate the wettability of FVB using the contact angle method after the alkali modification treatment. The method of this research was to use FVB frond of Salacca sumatrana Becc. which was treated with alkaline modification of the combination of NaOH+Na2SO3 at various concentrations. The results showed that the combination of NaOH 1M+Na2SO3 0.4 M had the smallest contact angle, which means that the FVB has a good wettability value compared to the control treatment. Based on the results, it can be concluded that the modification of NaOH+Na2SO3 can increase the wettability of FVB.

Electrocatalytic Oxidation of Glucose over Carbon Nanofiber-Supported Platinum Catalyst: Effect of Oxygen-Containing Surface Groups

With the transition towards the use of renewable feedstocks and renewable energy the use of bio-based molecules as feedstock and electro(catalytic) conversions gain in interest. Our target is to electrocatalytically convert starch to oxidized starch, which form a replacement for the currently used fossil based poly-acrylates. To develop efficient electrocatalysts for the oxidation process fundamental insights in catalyst property-performance relationships are essential. Since starch is a complex molecule we aim at getting these insights by using gradually more complex feedstocks, going from monomers to oligomers to polymers (e.g. from glucose to cellobiose to starch). Here we will show that for the electrocatalytic oxidation of glucose over Pt on carbon nanofibers (Pt/CNF), carboxylic acid groups on the carbon support have a positive influence on the catalytic activity, while hydroxyl groups have a negative influence. This is, also based on the influence of bulk pH effects, tentatively explained by local pH effects induced by surface oxygen groups.CNF supports were synthesized by chemical vapor deposition using CO/H2 and a Ni/SiO2 growth catalyst. After synthesis they were treated in sequential steps with 1M NaOH and 68% HNO3 to remove the growth catalyst and to introduce carboxylic acid and hydroxyl groups on the support (CNF-CA).1 Incipient wetness impregnation of Pt ammonium nitrate on CNF-CA followed by calcination was used to make the catalyst (5.0 wt.% Pt/CNF-CA). Pt/CNF-CA was heat treated at 300, 500 and 700 ˚C to gradually remove the support oxygen groups.1 The prepared electrocatalysts were drop-casted on a glassy carbon electrode to evaluate their performance for glucose oxidation by linear sweep voltammetry (LSV). The properties of the electrocatalysts were thoroughly analyzed by N2-physisorption, TEM, CO-stripping, TPD-MS, TGA, XPS, CV and titration.N2-physisorption, CO-stripping and TEM analysis showed that the physical properties of all electrocatalyst were similar: porosity (0.33 cm3.g-1), BET-surface area (182 m2.g-1), electrochemical surface area (120 m2.g-1) and the average Pt particle size (2.1 nm). The type and content of support oxygen groups of the electrocatalysts were assessed by CV, TPD-MS and TGA and revealed that the Pt/CNF-CA contains both carboxylic acid and hydroxyl groups on the carbon support surface. After treating the sample at 300 ˚C these carboxylic acid groups were removed and only hydroxyl groups were retained. After further increasing the treatment temperature the hydroxyl content decreased gradually. Therefore 4 different catalysts were prepared, i.e. with: carboxylic acid and high contents of hydroxyl groups (Pt/CNF-CA), and without carboxylic acid groups but with high, medium and low contents of hydroxyl groups (Pt/CNF-HO, Pt/CNF-MO and Pt/CNF-LO).The LSV measurements at pH 1 (Fig. 1A) show that Pt/CNF-CA has two oxidation peaks i.e., at 0.62 and 0.78V. This indicates that two oxidation processes occur, most likely the oxidative adsorption of glucose at 0.62 V and the oxidation of adsorbed glucose to δ-gluconolactone at 0.78 V.2 As the carboxylic acid groups were removed, going from Pt/CNF-CA to Pt/CNF-HO, the current densities decrease at 0.62 and 0.78 V. This decrease in current density indicates that the removal of carboxyl acid groups from the support results in a loss in catalytic activity. When the hydroxyl groups were removed, i.e., going from Pt/CNF-HO to Pt/CNF-MO to Pt/CNF-LO, the current density at 0.52 V increases, while the current density at 0.8 V remains unaffected. This increase in current density at 0.52 V represents an increase in catalytic activity for the oxidative adsorption of glucose for electrocatalysts with fewer hydroxyl groups on the support and might therefore affect the product distribution (currently under investigation). When the bulk pH of the electrolyte was increased from 1 to 3, it was found that Pt/CNF-CA is not affected by the pH, while at pH 3 the performance of all electrocatalysts that differ in hydroxyl content on the support (Pt/CNF-LO, P/CNF-MO and Pt/CNF-HO) resemble the performance of Pt/CNF-LO at pH 1. This is explained by the oxidation of the hydroxyl groups to carbonyl groups on the support resulting in the release of protons at pH 13 and thus a decrease in concentration of local hydroxyls in solution, which in turn hampers the electrocatalytic oxidation of glucose.The relation between the type and quantity of oxygen functionalities and current densities, shows that we can tune these oxygen functionalities to increase the catalytic activity, and simultaneously reduce the energy input (W=I*V) for the catalytic conversion. Our results also demonstrate how the type and presence or absence of support oxygen groups are related to the bulk pH, which in turn influences the catalytic performance of Pt towards the electrocatalytic oxidation of glucose.1)https://doi.org/10.1016/j.jcat.2004.05.0262)https://doi.org/10.1016/0022-0728(92)80454-C3)https://doi.org/10.1016/j.carbon.2013.07.082 Figure 1

RESISTANCE OF MORTAR WITH PPC CEMENT AND GEOPOLYMER MORTAR WITH WHITE SOIL SUBSTITUTION IN H2SO4 IMMERSION

<p class="IsiAbstrak">This study analyzes the effect of immersion of H<sub>2</sub>SO<sub>4</sub> (sulfuric acid) solution with a concentration of 10% on porosity, density and compressive strength of mortar with PPC cement and geopolymer with white soil substitution mortar. The purpose of this study was to determine the resistance of mortar with PPC cement and geopolymer with white soil substitution mortar when immersed in 10% H<sub>2</sub>SO<sub>4</sub> solution. The test object was 5x5x5 cm mortar with materials used including fly ash from PLTU Tanjung Jati B Jepara, white soil from Kupang, fine aggregate, water and alkaline activator in the form of a mixture of 8M NaOH and Na<sub>2</sub>SiO<sub>3</sub> and also PPC cement. The composition of the geopolymer mortar mixture is 1binder: 3Fine Aggregate: 0,5Water-Binder Ratio, while the mortar with PPC cement is made with a composition of 1PPC: 3Fine Aggregate: 0,5Water-Cement Ratio. The geopolymer mortar was made in 6 variations with a white soil substitution percentage of 0-25% with an increase of 5% for each variation. Compressive strength testing using a compression test apparatus. The test results show that the variation in the percentage of white soil substitution has less effect on the size of the porosity value. As for the value of compressive strength and density, white soil substitution has an effect, the higher the white soil substitution, the higher the compressive strength and mortar density values. Geopolymer mortar was better to withstand 10% sulfuric acid solution, while mortar with PPC cement had no resistance to 10% sulfuric acid solution because it continued to deteriorate over the course of the day. The greatest compressive strength is in variation IV (15% white soil substitution) of 15,31 MPa at 28 days of age, while the smallest porosity and greatest density are in variation VI (25% white soil substitution) of 0,17% and 2,205 grams/cm<sup>3</sup>.</p>

Removal of Toxic Copper Ion from Aqueous Media by Adsorption on Fly Ash-Derived Zeolites: Kinetic and Equilibrium Studies.

This study investigated the adsorption capacity of one material based on the treatment of fly ash with sodium hydroxide as a novel adsorbent for toxic Cu2+ ion removal from aqueous media. The adsorbent was obtained through direct activation of fly ash with 2M NaOH at 90 °C and 6 h of contact time. The adsorbent was characterized by recognized techniques for solid samples. The influence of adsorption parameters such as adsorbent dose, copper initial concentration and contact time was analyzed in order to establish the best adsorption conditions. The results revealed that the Langmuir model fitted with the copper adsorption data. The maximum copper adsorption capacity was 53.5 mg/g. The adsorption process followed the pseudo-second-order kinetic model. The results indicated that the mechanism of adsorption was chemisorption. The results also showed the copper ion removal efficiencies of the synthesized adsorbents. The proposed procedure is an innovative and economical method, which can be used for toxicity reduction by capitalizing on abundant solid waste and treatment wastewater.

Effect of Different Concentrations of Titanium Oxide (TiO2) Addition on the Crystallization Behaviour and Some Properties of Alkaline Earth Aluminosilicate Glass-Ceramics

Glass-ceramics in the CaO-MgO-Al2O3-SiO2 quaternary base glass system was produced via melting technique using feldspar, limestone and magnesite as sources of starting materials. Glass-ceramics production involves making a base glass, annealing and cooling to room temperature and then reheating the base glass to nucleation and crystal growth temperatures. Characterization of the produced glass-ceramics was carried out using a scanning electron microscope (SEM). The effects of the crystallization process on some properties such as hardness, chemical durability in acid and alkali media of samples were determined. The results portrayed that glass-ceramic samples to which various amounts of TiO2 (2,4,6,8 and 10 wt.%) were incorporated showed the formation of crystalline phases dispersed in the matrix of their respective residual glassy phases. Significant improvement in hardness, as well as minimum weight loss, were recorded for all the glass-ceramic samples. On the contrary, the glass samples did not crystallize despite subjecting them to heat treatment, their hardness values were low and they were not resistant to acid (1M HCl) and alkali (1M NaOH) attacks. The inability of TiO2 addition to fully transform them into glass-ceramics remains a shortcoming. However, the glass-ceramic samples obtained from this study can be used for tiling works.

Determination of myo-inositol content in milk by high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD)

A method to determine inositol content in milk using high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) was developed and validated. Samples were hydrolyzed with 10 mL HCl in a vacuum oven at 120oC, prolonging 6 h. Hydrolyzed samples were neutralized to a pH from 6 to 7.5 before analysing in an HPAEC-PAD system. The analytical program used Dionex CarboPacTM MA1 column (4 × 250 mm) with a mobile phase of a gradient program including NaOH 50 mM and NaOH 1M. The method was validated following AOAC guidelines: selectivity, linear range from 0,01 to 20 mg/L with a coefficient (R) 0.9998, the recoveries in the range of 99 - 102%, and repeatability with RSD under 1.8%. The limit of detection (LOD) and the limit of quantification (LOQ) of inositol were 0.047 µg/g and 0.155 µg/g, respectively. The method has been applied to determine of inositol content in milk samples with content ranging from 22.5 mg/100g to 64.7 mg/100g.

Photocatalytic degradation of low-density polythene using protein-coated titania nanoparticles and Lactobacillus plantarum

ABSTRACT The biodegradation of low-density Polyethylene (LDPE) is usually time-consuming, In the presence of Titania-nanoparticles, LDPE is photocatalytically degraded in smaller fragments afterward the bacteria can effectively degrade polyethylene. In the current study, potent polyethylene degrading bacteria were screened from the soil of the local dumpsite and identified using 16s rRNA sequencing. The protein-coated titania nanoparticle (TNPs) was synthesized using Sol-gel Method and characterized by XRD, and SAED-HRTEM. The photocatalytic biodegradation of LDPE (30 microns) in presence of 1M NaOH was studied by exposing it to UV irradiation, visible light, and high temperature (50°C) for 21 days separately and photocatalytic biodegradation was assessed by monitoring % weight loss at every 7 days’ time interval, tensile strength, and FTIR. After 21 days of photocatalytic biodegradation, LDPE film containing both TNPs and Lactobacillus plantarum along with 1M NaOH in presence of visible light was unveiled oxidation and enumerated via the occurrence of strong absorptions band of the carbonyl group (C=O) and also the breaking and weakening of existing absorptions bonds along with the new carbonyl functional group formation. The decline in tensile strength was measured at 21% after 21 days. Thus, experimental results on LDPE after exposure to visible irradiation along with Lactobacillus plantarum and 5% protein-coated TNP showed improvement in degradation rate and elongation 59 % and 51% within 21 days, respectively in comparison to another study (49 % Weight loss and 12% elongation after 45 days). An excellent application of this research is significantly reduced plastic waste via a maintained procedure.

Effect of different aqueous electrolytes on electrochemical behavior of LiFePO4 as a cathode material: Lithium ion battery and renewable energy nexus

Lithium iron phosphate as a cathode source is synthesized by a simple hydrothermal synthesis route and its electrochemical performance in different aqueous electrolytes, such as 2M NaOH, 1M Na2SO4, 1M KOH, and 3M KOH is investigated. X-ray diffraction revealed orthorhombic olivine structure with Pbnm (62) space group and lattice parameters a = 4.98 Å, b = 10.04 Å, and c = 5.89 Å. Field emission scanning electron microscopy analysis shows disc form morphology with a particle size distribution in the range of 150 nm -600 nm. In the Raman spectroscopy, the sample's intense peaks at 1390 cm−1 wavenumber indicate the higher ratio of disordered carbon deposit as carbanions material deposited on the LiFePO4 particles.The cyclic voltammetry study confirms the redox reactivity of the LFP cathode and is used to measure the diffusion coefficient of the carrier ion for each electrolyte.Electrochemical impedance spectroscopy is used to predict the chemical kinetics and mass-limitations in the cell.Experimental results showed that the electrochemical efficiency of LiFePO4 can be significantly affected the electrolytes, the maximum peak current, diffusivity, the charge transfer resistance is optimal in case of 1M KOH in comparison to Na2SO4 as well as NaOH.

Impact of Synthetic Parameters on the Compressive Strength of Bagasse Ash-Clay Geopolymer

The impact of different parameters on the compressive strength of geopolymer synthesized from clay and bagasse bottom ash is reported. Geopolymer was synthesized from thermally activated clay and bottom bagasse ash using sodium silicate and sodium hydroxide as activator. The maximum dissolution of alumina and silica from the bagasse ash and clay maintaining different alkali conditions is studied. The resulting geopolymer synthesized under different conditions is studied for compressive strength. Different characterizations of the resulting geopolymer were carried out using different analytical instruments. The results indicated that the dissolution and strength of geopolymer have close relationships with the alkali concentration, solution to solid ratio and curing period. The highest compressive strength of 25 MPa was observed for 8M NaOH, 24 MPa for 0.3 solution to solid ratio, 30 MPa for 60% clay and 30 MPa for 27 days of compressive strength.

Synthesizing of Zeolite Particle Using Alkaline Plant Extract

The study explored the hydrothermal synthesis of zeolite using kaolin clay precursor in the presence of three different solvents namely, garlic extract, watermelon extract and 2M NaOH solution, with the view of testing their efficacy and potency for green synthesis. Before the zeolitization, the kaolin precursor was activated at a temperature of 850°C to produce metakaolin. The crystallization was achieved in an oven at a temperature of 90°C for 12 hours. The final product is grounded to a fine powder and subsequently undergo testing and characterization via X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopes (FESEM) methods. The purity and grade of the synthesized products vary accordingly with the suitability of the reaction solvent. The synthesized product using a solvent of watermelon plant extract was able to produce zeolite LTA of a good grade. However, the presence of secondary phases informed the effect of the accompanied impurities that might originate from the kaolin precursor or the solvent. The result also portrays the possibility of obtaining a well crystalline zeolite from the Malaysian kaolin without using any structural directing agent or chemical solvents.

Assessment of hydrothermal parameters on alkaline activation of fly ashes using a central composite design

Coal fly ash (CFA) is a powder generated during combustion of coal; its improper disposal constitutes an environmental issue. To minimize this problem, one of the uses of CFA is as feedstock for production of zeolite. Different studies have shown that zeolites may be easily obtained from CFA by relatively cheap and fast conversion processes. Most of these studies have been focused on the study of the zeolite synthesis using classical methods through changing one factor per time and fixing the other factors, where it illustrates the impact of each variable individually via a huge number of experiments, however it doesn’t consider the effect of the interaction between different factors under study. This study aims to evaluate the effects of hydrothermal synthesis parameters, time of activation (t), temperature of synthesis (T) and concentration of alkaline activator ([NaOH]), on the formation of zeolite. Morphological and structural properties were determined through scanning electron microscopy and X-ray diffraction. The experiments were designed through a central composite design. The results revealed that 4M NaOH, 90℃ and time synthesis of 36 h were the conditions for a higher conversion of CFA into sodalite, furthermore, it was obtained P1-Na and losod as zeolite phases.

Zero-Sum Space on the Copper Surface Under Ultrasound

In the overlapped shell space between two adjacent cavitation bubbles, there theoretically exists a Zero-sum space without vibration due to the cavitation effect but still with pressure, high temperature and a high concentration of substances. Within the Zero-sum space, a stable environment for a chemical reaction is achievable under the ultrasound. In this work, some ring-shaped regions (outer diameter 48.90±3.5 μm, inner diameter 40.94±3.5 μm) on copper foil with distinctive morphology were investigated in the area covered by visible bubbles under ultrasound treatment in 1M NaOH for 3 h. The morphology and composition of these regions were found to be similar to that of sample fabricated in the same environment without ultrasound. It has confirmed the long-term existence of Zero-sum space and raised a hypothesis of Zero-sum space maintenance. This work may lead to release the ultrasonic synthesis from the limitation of ultrasonic frequency.

ASPHALT CONCRETE MIXTURE PRODUCED USING RECLAIMED ASPHALT PAVEMENT AND FLY ASH AS ARTIFICIAL AGGREGATE AND FILLER

This study presents the use of reclaimed asphalt pavement (RAP), and fly ash as artificial aggregate and filler in asphalt concrete. Because of the limited availability of natural materials, infrastructure development has become a concern. Therefore, it is necessary to reuse and recycle waste materials. One such innovation is artificial aggregates. The disadvantage of RAP is that its gradation exceeds the standard; its asphalt penetration and ductility exceed the requirements. The weaknesses of artificial aggregate are high water absorption, spherical shape, and low aggregate interlocking. In this study, the artificial aggregate was produced using the fly ash and alkali activator. Alkali activator consisted of Na2SiO3 and 8M NaOH at a ratio of 2.5. The mixtures containing different percentages of artificial aggregate (45, 55, 65, and 75%) were produced, and the fly ash filler content was 5%. Different tests including XRF, SEM, and Marshall tests were conducted. The artificial aggregate is hydrophilic owing to the high silica content; thus, it has high water absorption. This results in a low adhesion between the asphalt and aggregate. The best composition of asphalt concrete is 55% artificial aggregate, RAP, fly ash filler, and asphalt. The asphalt concrete containing artificial aggregate has high stability and is stiff and light. However, it requires a high asphalt content because of high water absorption. It is unsuitable for application in high traffic roads but suitable for medium traffic ones.

How Co-Precipitation Reaction Parameters Control the Characteristics and Features of Iron Oxide Nanoparticles

The main purpose of this study was to find a simple reaction condition for reproducible synthesis of water-soluble superparamagnetic iron oxide nanoparticles (SPIONs) through the co-precipitation method. For this purpose, the effect of alkali solution, working atmosphere and final reaction temperature on type, size and magnetic properties of synthesized particles were examined. The results reveal that from two different tested alkali precipitants including ammonia and 1M NaOH, samples synthesized using ammonia demonstrate proper magnetic properties, while the latter agent leads to production of nonmagnetic brown suspensions in all reaction conditions. UV-Vis and XRD showed the typical magnetite pattern for samples synthesized using ammonia as the alkali precipitant. In addition, the results show that higher reaction temperatures lead to the production of smaller size black particles with lower oxidation level, better crystallization, and higher saturation magnetization. The optimal results were obtained when the ammonia was used as an alkali precipitant and the reaction temperature was set to 80 C under N2 atmosphere. Furthermore, particles which were made under the air condition at 80 C using 25% ammonia, showed satisfactory dimensional and magnetic properties. The simple reaction condition used in this study could be applicable for large scale synthesis of stable SPIONs.

Application of self-produced artificial sand in the production of green mortar

Due to the large disposal of locally industrial wastes and the shortage of natural resources, turning industrial by-products into green artificial materials has been attracting many researchers in the world. Following this trend, this study evaluated the potential application of self-produced artificial sand (AS) in the production of green mortar. The AS was produced by the alkali-activated method using a mixture of 36.4% fly ash, 36.4% slag, 3.5% 10M NaOH solution, 11% Na2SiO3 solution, and 12.7% water. The mortar mixtures were designed based on the densified mixture design algorithm with the incorporation of the AS as the substitution of natural sand (NS) by 0 – 100 wt.% (interval of 20%). The engineering properties of the mortar samples in both fresh and hardened states were evaluated through the tests of workability, compressive strength (CS), water absorption (WA), and shrinkage/ expansion. The experimental results showed that the mortar sample incorporating 20% of AS to replace NS performed superior engineering properties in comparison to other samples. Further increasing the AS content generally caused a negative impact on the mortar’s performance. Increasing AS content beyond 20% systematically decreased the CS while both WA and expansion were increased noticeably. However, the properties of the green mortar produced for this study satisfied all of the requirements of the official Vietnamese standards. Thus, the research results further confirmed a great potential in producing green mortar using AS to either partially or fully replacement of NS. In addition, the use of AS greatly contributes to not only saving natural resources but also limiting the negative effects on the environment due to the exploitation and use of naturally sourced materials.

Nanoporous Amorphous Fe78Si9B13 Alloys for Hydrogen Evolution in Alkaline Media

A serious of corrosion treatments are applied upon a melt-spun amorphous Fe78Si9B13 alloy to fabricate nanoporous structure for improving the alkaline hydrogen evolution reaction (HER) performances. The corrosion treatment produces a large number of nanopores on the surface, leading to remarkably improved HER performances. By corroding in 2M NaOH solution for 120 min, abundant pores with a diameter of about 50~100 nm were uniformly formed on the surface of the amorphous alloy. The nanoporous amorphous alloy can obtain a current density of 10 mA cm−2 at the overpotential of only 199 mV in 1M KOH environment, which is significantly reduced from that of the original melt-spun alloy of 386 mV under the same conditions. The corroded sample also shows excellent cycling performances. Microstructural study shows that after 1000 CV cycles the nanoscale columnar structure formed on the surface of the corroded sample are denser and larger than that of the melt-spun alloy, which effectively inhibit the increase range of the polarization resistance of the alloy.

Effect of Thermo-Chemical Pretreatment of Kenyan Market Waste on Mesophillic Biogas Production

Effects of pretreatment on the anaerobic digestion of waste fruit and vegetable market waste were investigated in biogas production by batch experiments. The pretreatment was NaOH and HCl thermochemical, thermal and chemical methods. The wastes were chopped and blended before loading to the digester. Acid hydrolysis was done by adding 20ml 0.1M HCl with thorough mixing before purging with CO2 and sealing. Alkaline pretreatment was done using 1M NaOH. In both cases, the setups were exposed to heat at 1000C for 12hours, after which they were allowed to cool for 3 hours. The pH was modified to 6.7 – 7.2 before loading the inoculum and studying biogas generation. The large-scale setups with 1.0l, 1.5l, 5l and 10l capacity were studied for biogas generation. The results obtained show that thermochemical pretreatment results in more cumulative biogas production at 6200ml, followed by thermal at 4900ml and then chemical pretreatments at 3750ml for 500g mixed fruits and vegetable market wastes. Alkaline pretreatment is more efficient compared to acidic hydrolysis though highly influenced by proximate properties of the wastes and operation pH. The large-scale pretreatment resulted in 34500ml and 31400ml cumulative biogas from HCl and NaOH pretreatment. In conclusion, thermochemical pretreatment of market waste results in increased biogas generation resulting from hemicellulose breakdown and disrupting lignin-hemicellulose ether bonds in acid hydrolysis. In contrast, alkaline pretreatment leads to swelling of lignocelluloses and partial lignin solubilization lignin breakdown. The overall biogas generation depends on proximate waste matter and digester operation pH.

Residential Indoor Radon Assessment in the Vicinity of some Dumpsites in Lagos, Nigeria

Dumpsites in Nigeria are generally open and significantly elevate the pollution and contamination level of the total environment. Indoor radon was measured with CR-39 detectors in some buildings in the vicinity of dumpsites in Lagos, Nigeria. Eight (8) dumpsites (4 dormant and 4 active dumpsites) were chosen for this study. Detectors were exposed in 50 houses randomly selected within 0 and 100m away from the dumpsites. The detectors were exposed for 3 months. They were then retrieved and etched in a 6M NaOH solution in a water-bath at a temperature of 90o C for 3 hours. Tracks were counted using a semi-automatic system with a DCE camera mounted on a microscope and connected to a PC. Radon concentration ranged from 24.00±4.86 to 656.00±131.20 Bqm-3 in the active dumpsites.Mean concentrations were 120.3±24.0, 257±51.4, 179.8±33.6, and 131.5±19.4, respectively in Oke-Odo, MRF, Olusosun, and Solus-3. In the dormant sites, concentration ranged from 16±3.2 to 931±186.3 Bqm-3 having means of 194.17±38.80, 206.75±41.33, 223.25±44.69, and 334±66.85Bqm-3 , respectively in Oke-Afa, Solus-1, Solus-2, and Solus-4. The annual effective dose and cancer risk in the active and dormant dumpsites were (3.60 mSv, 8.97 per million person-yearly) and (4.53 mSv, 12.47 per million person-yearly), respectively. This study revealed some high value of radon concentrations in some houses close to the dormant dumpsites than in the active dumpsites. This is unsafe and can cause severe health issues in the long term.
 Keywords: Radon, dumpsites, Olusosun, CR-39, buildings, Lagos state, SOLUS