Papers by Keyword: pH

Abstract: The main purpose of this study was first to investigate the removal of Hg(II) ions from industrial wastewaters by coagulation-flocculation with aluminum sulfate, secondly to understand the contribution of some parameters including the coagulant dose, pH, and the addition of adjuvant (activated carbons and lime). Jar-test experiments were carried out on wastewater samples containing mercury from the industrial area of Biskra (BIWW: Biskra industrial wastewater, C₀= 1.01 mg/L) and Tizi Ouzou (TOIWW: Tizi Ouzou industrial wastewater, C₀= 1.81 mg/L).The maximum elimination of mercury at ambient temperature was 49% and 58% that were obtained with concentrations of 180 mg/L and 200 mg/L of aluminum sulfate at a pH close to 7 for both Tizi Ouzou and Biskra samples, respectively. The obtained results showed that the removal efficiency of mercury ions is improved by the addition of adjuvant (activated carbon and lime). The removal efficiency of Hg (II) ions increased with increasing lime and activated carbon masses, experiments results indicated that the yield increased with the increase in the dose of the adjuvant to reach a maximum of 82.89% (TOIWW) and 83.38% (BIWW).The experiments were conducted to test the ability of coupling coagulation-flocculation to adsorption. It was verified that coupling was more efficient in the removal of Hg(II) ions from industrial wastewater than coagulation-flocculation alone. Almost complete removal (99.42) of Hg was obtained by coupling coagulation-flocculation and adsorption on powdered activated carbon.Accordingly, it is believed that coupling coagulation-flocculation and adsorption are practical for utilization in industrial wastewater treatment for mercury removal.

Abstract: Group III–V compound semiconductors are attracting attention as new channel materials that have higher carrier mobility than Si. However, defects easily occur at the interface between the semiconductor and insulator film, which degrades performance. In an earlier study, we demonstrated that the interfacial properties of InP are degraded by the growth of In₂O₃ and that In₂O₃ grows better in water than in air. Therefore, it is necessary to suppress the growth of In₂O₃ to improve the interfacial properties of InP. In this work, we focused on functional water, which can be controlled by adjusting the water conditions, and investigated the growth behavior of In₂O₃ in functional water. As a result, we found that the growth is suppressed in the low-pH range and in hydrogen water. It is important that H⁺ ions reduce OH⁻ ions, which contributes to the reaction with InP.

Abstract: This paper deals with the development and research of low pH concrete mixtures intended for the deep geological repository for radioactive waste. Mixtures, in particular those made from materials originating in the Middle Europe, specifically Czech Republic, were designed due to the diversity of the raw materials’ properties. In this first part, a large number of cement mortars were designed, on which the effect of active ingredients (microsilica, slag) on the pH value over time were tested. From the results of the cement mortars’ pH measured after 90 days, a concrete formula was designed. A mixture with a lower proportion of cement and a higher proportion of microsilica seems to be the best. The slag serves only as a supplement in the place value of several weight percent of the total binder volume. Also, the control measurements of basic material characteristics, such as volumetric mass density and compressive strength were performed on these mixtures.

Abstract: Drilling additives play a unique role during drilling operations, from aiding in the control of various drilling challenges to successfully enhancing downhole drilling efficiency. pH enhancers are amongst the plethora of additives imported into Nigeria at exorbitant prices to aid in drilling operations. These additives includes NaOH, Na₂CO₃, Ca (OH)₂ etc. These additives are used to improve the mud pH and mitigates drill string corrosion. The high cost of importation of these additives, has warranted the need for product substitution which should take advantage of the locally available resources. This paper evaluated the suitability of locally-sourced Trona, as a mud additive in drilling mud. Trona is known chemically as Sodium Sesquicarbonate or Sodium Hydrogen Carbonate. A distinguishing factor in this research work was the purification of Trona by extracting the compound of interest (Na₂CO₃) from it using the monohydrate process. The purification method involved crushing and screening of Trona as well as calcination, filtration and evaporation processes. The analysis of the Trona and the extracted product was performed using quantitative analysis and characterization tools such as FTIR and EDX. Further experimentation was carried out to evaluate the effects of the extracted sodium carbonate on the mud pH, rheology, and density of the water-based mud. The results were also compared to the results gotten from the addition of conventional Na₂CO to similar mud samples. The extracted Na₂CO was observed to increase the pH of the mud samples from 8.73 to 9.52 and the commercial Na₂CO increased it from 8.73 to 10 and this value is still in the range of API standard. The pH enhancers from both sources also had effect on the mud rheological properties. This indeed showed that the extracted Na₂CO from Trona acted as drilling fluid pH enhancer and hence possess the potential for usage in the industry.

Abstract: Crude laccase was produced by using the fermentation method of solid state fermentation and employed fungus Marasmius sp and rice straw as support media. The kinetics of laccase was investigated by using the substrate of 2,2’-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). Laccase exhibits the maximum activity (V_m) of 1.45 mM/min and Michaelis-Menten (K_m) constant value of 4.11 mM. The effect of pH and temperature has also been evaluated. The results showed that this enzyme had an optimum pH of 4.6 and temperature of 60 °C. Decreased stability of laccases is found to be faster when stored at room temperature than cold temperatures.

Abstract: Adsorption of Au(III) and Cu(II) by mangosteen rind adsorbent had been carried out. Mangosteen rind has several functional groups including –OH phenolics, ‒C=C‒ aromatics, and ethers. Dried mangosteen rind which was obtained from maceration was used to determine Point of Zero Charge (PZC). The most effective pH adsorption was determined by mixing adsorbent with Au(III) or Cu(II) solutions with various pH. The adsorption capacity was affected by the interaction between adsorbent and adsorbate. The solid adsorbent before and after interaction was characterized by FTIR, XRD, and microphotography. The PZC pH value of adsorbent was 3.7 while the optimum pH for Au(III) and Cu(II) were at pH 2 and pH 5, respectively. The adsorption capacity (q_max) value was 333.33 mg/g by following the Langmuir isotherm equation. The crystalline structure of adsorbent was analyzed using XRD and gave 4 peaks characteristics of gold metal on 2ϴ = 38º, 44º, 64º, and 77º after adsorption which indicated the reduction of Au(III) ions into Au(0).

Abstract: Inhibitor is a chemical compound which commonly used to control corrosion in a tank or a pipelines. Organic inhibitor recently developed because of the availability and the ability to act like commercial inhibitor. The performance of mixed inhibitor was studied on St 41 carbon steel immersed in NaCl solution containing CO₂ gas. Research parameter used were pH 4 and 6, rotation speed of 150 and 250 rpm, with mixed inhibitor volume ratio of 1 (imidazoline) : 2 (paracetamol), 1:1, also 2:1. The Weight loss measurement, isotherm adsorption calculation, FTIR, and XRD measurement have also been done. Based on weight loss test, the highest inhibitor efficiency was 61.412 % at pH 6, 150 rpm, with inhibitor volume ratio of 2:1, adsorption isotherm calculation indicate the adsorption mechanism of the mixed inhibitor is physical adsorption. Tafel test result showed the tendency of inhibitor worked anodically. The FTIR spectrum result found functional group of N-H from the inhibitor precipitated on the metal surface after ten days of immersion Based on the EIS result, there was an increase value of polarization resistance value and decrease on CPE (constant phase element) value. While X – ray diffraction (XRD) result from the volume ratio of 1:2 confirm the CO₂ corrosion product FeCO₃ and Fe₂O₃ formed on metal surface. With volume ratio of 2:1 mixed inhibitor, it was confirmed that iron nitride (Fe₂₄N₁₀) compound was formed on steel surface because of the chemisorption reaction between Fe and nitrogen atom from pyridine at the imidazoline inhibitor. The inhibition mechanism was physisorption for entire parameters, based on calculation of Langmuir adsorption theorem.

Abstract: Resorability of 3D printed hydroxyapatite (3DP HA) in deionized water solution which was buffered with succinic acid-NaOH (pH 5.5) and Tris(hydroxymethyl aminomethane) (pH 7.4) for 1, 7, 14 and 28 days was carried out. Weight change and release of calcium (Ca) and phosphorus (P) were used to evaluate the sample resorption. It was found that the weight of samples soaking in both pH 5.5 and 7.4 solutions decreased with increasing soaking times, but the degree of decrease was greater at pH 5.5 than at pH 7.4. ICP-OES results showed that the release of Ca and P in both pH solutions increased with immersing times. The amount of Ca and P released at pH 5.5 was higher than at pH 7.4. Phase composition of the samples and the microstructure of the sample were characterized using XRD and SEM respectively. XRD analysis showed that hydroxyapatite (HA) and octacalcium phosphate (OCP) phases were found at the center of all samples, but the intensity of OCP peaks tended to decrease with increasing times. Only HA was found on the sample surface after immersion in both pH solutions at all soaking periods. After immersion, newly formed crystals were seen both at the center and/or on the surface of samples. These results suggested that pH could influence the resorption of the samples and also the formation of new calcium phosphate crystals.

Abstract: Recently, coal is still one of the main sources of energy. From a coal combustion process, a huge amount of coal waste such as bottom ash is generated. The most common method for coal-waste disposal is a landfill which creates the environmental problems. However, the coal-waste utilization like soil amendment is a better way to manage the waste as well as to reduce the environmental impacts and to increase the profit for the manufacturers. Therefore, the objectives of this study are to measure the properties of soil mixed with bottom ash from coal waste and to apply the bottom ash to improve the soil quality by growing one types of plants, chili, and to compare the results with the normal soil and soil with fertilizer. The operating parameters of this study are the compositions of coal-waste mixed with soil and fertilizer ranging from 0 to 30%wt. Furthermore, the pH, bulk density as well as soil texture are also measured and studied. From the results, it is found that bottom ash can help growing both plants especially chili with 10%wt bottom ash.

Abstract: Silver nanoparticles were synthesized using silver nitrate as a silver precursor in the presence of tannic acid under UV radiation for 60 minutes. Various pH conditions were employed in the synthesis in order to study its effect on characteristics and ammonia sensing of the synthesized nanoparticles. The images obtained from transmission electron microscope revealed the formation of the spherical particles with average diameters in the range of 10-40 nm depending on pH conditions. It was found that using acidic condition resulted in yellow silver nanoparticles colloids with bigger particles and exhibiting a UV-visible absorbance peak at around 435 nm whereas using other conditions yielded greenish-yellow colloids with smaller particles and having two absorbance peaks at around 370 and 430 nm. After adding 100 ppm of ammonia, TEM images revealed the aggregation and the changes in size and shape of the silver nanoparticles. The color of the silver nanoparticles colloids synthesized using acidic condition changed to orange-yellow color. However, other pH conditions caused the color of the colloids became darker. These color changes were observed by the naked eyes.