Papers by Keyword: Sulfate

Abstract: Laboratory activities for testing nitrogen levels of natural rubber production are carried out to determine the nitrogen content to meet the Standard Indonesian Rubber (SIR). The test parameters use hazardous chemicals such as strong acids, i.e. sulfuric acid, which have corrosive properties. Testing activities in the laboratory will produce by-products in the form of liquid wastewater containing high sulfate concentrations. A cheap and environmentally friendly wastewater treatment system is required in this research, namely a coagulation-flocculation system using eco-enzyme as a liquid coagulant. Eco-enzyme is a fermented product of household organic waste from the remaining vegetables and fruit peels that are still fresh with a 1:3:10 formula after around 3 months. The purpose of this research was to determine the levels of COD, TDS, and sulfate concentrations as an indicator of wastewater quality standards that are safe for the environment. It is necessary to know the effectiveness of the eco-enzyme as a coagulant in treating laboratory wastewater with various concentrations of 1, 5, 10, 20, and 40% v/v. As well as variations in monitoring time of 5, 10, 15, 20, and 30 days. In this study, laboratory waste treatment with Eco-Enzyme as a coagulant resulted in a decrease in sulfate levels at 29.8 mg/L found at 1% v/v Eco-Enzyme concentration with monitoring for 30 days. With levels of COD 263 mg/L, TDS 39.7 mg/L, and pH 7.01 at a concentration of 40% v/v Eco-Enzyme. The results of this study indicate that Eco-Enzyme can act as a natural coagulant that is environmentally friendly and can degrade laboratory liquid waste so that it meets wastewater quality standards that are safe for the environment.

Abstract: In this study, it investigated the micropore changes by aging of LCD waste glass powder and investigated the effects of particle size and replacement ratio on sulfate erosion. Also, the comparison of the compressive strength with that of OPC concrete was carried out to evaluate the sulfate resistance of the LCD waste glass mixed concrete. As a result, resistance to sodium sulfate is better than magnesium sulfate.

Abstract: Sulfate is a pollutant present in the mining waste water and acid mine drainage. High levels of sulfate can generate important environmental problems. One of the alternatives proposed for the treatment of water with high levels of sulfate is the use of sulfate-reducing microorganisms. This work describes the synergistic combination of a treatment system for the removal of metals by biosorption with the strain Bacillus sp. NRRL-B-30881 to reduce the inhibiting concentration of metals in waters, followed by a new process of sulfate removal that uses a halotolerant sulfate-reducing microbial consortium. The results show that the sulfate reducing consortium can be cultured and is able to reduce the sulfate concentration using cheaper complex organic substrates like spirulina, cellulose and industrial starch. The sulfate reducing consortium was cultured on a bioreactor with Celite R-635, as support material. Using this bioreactor it was possible to reduce the sulfate concentration in the culture medium in batch or semi-continuous operation. An acid mine drainage was pretreated by lime and treated by biosortion in order to increase the pH and reduce the heavy metals concentration. Subsequently the remaining sulfate was removed by the developed process. This integrated biological process represents a more economical alternative for the removal of metal by biosortion and the removal of sulfate using a sulfate reducing consortium.

Abstract: The utilization of fly ash not only reduces the environmental impact but also improves some mechanical properties and durability of concrete. However, the early-age strength of fly ash concrete is sometimes lower than that of normal concrete due to the slow pozzolanic reaction of fly ash. In recent years, some researchers have suggested alkali or sulfate activation to accelerate the pozzolanic reaction. Some studies have used sodium hydroxide (NaOH) solution, while others have applied potassium sulfate (K₂SO₄) or sodium sulfate (Na₂SO₄) as activators which are effective in accelerating the pozzolanic reaction and increasing the strength at early age. On the other hand, the early-age strength of fly ash concrete is also improved by using porous ceramic aggregate (PCA) as an internal curing agent. Therefore, the present study aims at investigating the effect of an internal activating agent using PCA on hardness and pore structure of fly ash cement paste. In the experimental program, PCA immersed in two kinds of solution (K₂SO₄ and Na₂SO₄) was placed in the center of specimen with dimension of 21x21x20 mm. In addition, normal aggregate (NS) was used for reference. As a result, internal sulfate activation using PCA improved the hardness of interfacial transition zone (ITZ) between paste and PCA, and reduced the Ca(OH)₂ content in cement paste with 40% replacement with fly ash significantly at the age of 1 day, but negligibly at the ages of 7 and 28 days when compared with reference specimen. K₂SO₄ was more effective in improving hardness of ITZ as an internal activating agent than Na₂SO₄. Although the total pore volumes of the fly ash cement pastes using PCA imbibing sulfate activators were not reduced at the age of 28 days, their pore volumes with diameters less than 0.05 µm were increased.

Abstract: The efficiency of chalcopyrite bioleaching in a high sulfate background was evaluated using acidophilic microorganisms adapted to sulfate. The concentration of magnesium sulfate added to mesophilic, moderately thermophilic and thermophilic bioleaching tests was equivalent to 100, 40 and 80 g L^-1 SO₄^2-, respectively. Biological copper extraction was highest at 45 °C (67 %), followed by 60 °C (54 %) and 30 °C (16 %). Quantitative x-ray diffraction (QXRD) analysis of the ROM ore and bioleached residues revealed the complete disappearance of pyrrhotite and a significant reduction of pyrite at all temperatures. Significant chalcopyrite was leached at 45 and 60 °C; however, no chalcopyrite was leached at 30 °C. As the bioleach did not plateau after 31 days, it is possible that higher copper yields may have been achieved with prolonged leaching.

Abstract: In the present paper the durability of fly ash geopolymer mortars compared to that of cement mortars is investigated. Geopolymers can improve the ecological image of building materials, especially when their production is based on industrial by-products such as fly ash. Three series of fly ash based geopolymer mortars were prepared using calcareous sand to fly ash ratio (S/FA) varying from 0.5 to 2. In addition, cement mortar specimens were prepared using cement CEM I 42.5 N and CEM II 32.5 N. Durability of geopolymer and cement mortars was evaluated by means of compressive strength development, acid resistance, chloride diffusion and sulfate resistance. It was found that fly ash can be effectively used to produce geopolymer mortars with calcareous sand. Geopolymers exhibit competitive compressive strength compared to that of cement mortars. Geopolymer mortars develop their maximum compressive strength a few days after their casting. Geopolymer and cement mortars exhibit satisfactory resistance to sulphate attack. Cement mortars, generally, show better behaviour (compared to geopolymers) in chloride diffusion. Finally, geopolymers indicate improved performance against acid attack, compared to that of cement mortars.

Abstract: Double-chambered microbial fuel cells (MFCs) were used to investigate the effect of sulfate and sulfate-reducing bacteria (SRB) on electricity generation by molybdate inhibition coupled with PCR-DGGE technique. Results showed that low influent sulfate (< 1470 mg/L) improved power density and voltage, while higher sulfate blocked the MFC efficiency. Molybdate inhibited the activity of SRB and consequently decreased MFC voltage and power density which confirmed some SRB were involved in the electricity generation. Microbial community analysis indicated that Desulfovibrio desulfuricans contributed to the electricity production and stability of MFC.

Abstract: Three polyvinyl chloride (PVC) columns filled with different ratios of reactive media, ceramsite and corncob, were conducted to assess the treatment performance of simulated acid mine drainage (AMD). The results indicated that the columns could effectively remove sulfate and metal ions from AMD with the removal efficiency of 57.7% and 96.5% respectively. The removal efficiency decreased with the increasing inlet velocity and at the same sample ports the sulfate and metal ions concentrations at the velocity of 1 ml/min were lower than that at the velocity of 2ml/min and 3ml/min.

Abstract: To better regulate (up and down) the activation of SRB thereby contributing to EOR, efficiency of growth and inhibition of SRB was studied in this paper.Six different growth media were tested in total.The optimal growth media were selected based on growth rate and variations of pH between the start and end point of growth. Of the six media, complex I was selected as the best medium in which SRB grew to stationary-phase in less than 8 days with the highest cells’ concentration. Finally, the effects of NO₃^- on growth and persistence of SRB were studied by using abroad range concentrations of NO₃^-. The result indicated that SRB growth could be significantly inhibited at NO₃^- of 80 mM.

Abstract: To better understand the roles of microorganisms in oil production, diversity and distribution of microbes in Jilin oilfield was studied. Firstly, chromosomal DNA wassuccessfully extracted directly from crude oil samples. Diversity and distribution of microbes was then analyzed based on 16S rDNA libraries. There were totally 21 OTUs were obtained through 16S rDNA sequencing. Of those OTUs, 13 are bacteria in which Proteobacteria is the major family, while 8 are archaea in which Methanomicrobia is the dominant. Finally, SRB was found in all samples by amplifying the apsA gene using PCR. SRB found in Jilin oil samples belong to δ-Proteobacteria.