Pengaruh Konsentrasi Natrium Silikat Terhadap Laju Korosi Paduan Aluminium dalam Lingkungan Natrium Klorida 3,5%

<p><span id="docs-internal-guid-16dbe470-7fff-c41c-0744-77bf71d25737"><span>Korosi merupakan proses penurunan kualitas logam akibat reaksi logam dengan lingkungannya. Air laut merupakan salah satu sistem yang korosif karena tingginya kadar ion klorida. Ion silikat dengan konsentrasi optimum mampu memperlambat laju korosi pada logam, seperti aluminium. Penelitian ini menguji pengaruh ion silikat dalam larutan natrium klorida 3,5% terhadap laju korosi aluminium yang diuji dengan metode potensiostat dan dihitung dengan Ekstrapolasi Tafel. Pengaruh konsentrasi ion silikat terhadap laju korosi diamati pada variasi konsentrasinya yaitu 0, 25, 50, 75, dan 100 mM. Konsentrasi optimum natrium silikat untuk menurunkan laju korosi adalah 25 mM, laju korosi turun dari 0,0118 menjadi 0,0084 mm/tahun. Sebaliknya, penambahan konsentrasi natrium silikat hingga 100 mM, dapat meningkatkan laju korosi menjadi 0,101 mm/tahun.</span></span></p><p><span><span><span id="docs-internal-guid-17392559-7fff-0660-df12-7a65eee22bac"><span><strong>The Effect of Sodium Silicate Concentration on the Corrosion Rate of Aluminum Alloy in Sodium Chloride 3.5%.</strong> </span><span>Corrosion is a process of decreasing the quality of metals due to the reaction of metals with their environment. Seawater is one of the corrosive systems because of the high levels of chloride ions. Silicate ions with optimum concentrations can slow the rate of corrosion in metals, such as aluminum. This research examines the effect of silicate ions on the aluminum corrosion rate in a solution of sodium chloride 3.5%, tested by the potentiostat method and calculated by Tafel extrapolation. The effect of silicate ion concentration on the corrosion rate was observed in various concentrations of 0, 25, 50, 75, and 100 mM. The optimum concentration of sodium silicate in reducing the corrosion rate is 25 mM, in which the corrosion rate drops from 0.0118 to 0.0084 mm/year. Conversely, increasing the concentration of sodium silicate to 100 mM increased the corrosion rate to 0.101 mm/year.</span></span></span></span></p>

Pengaruh Konsentrasi Natrium Silikat Terhadap Laju Korosi Paduan Aluminium dalam Lingkungan Natrium Klorida 3,5%

<p><span id="docs-internal-guid-16dbe470-7fff-c41c-0744-77bf71d25737"><strong>ABSTRAK.</strong><span> Korosi merupakan proses penurunan kualitas logam akibat reaksi logam dengan lingkungannya. Air laut merupakan salah satu sistem yang korosif karena tingginya kadar ion klorida. Ion silikat dengan konsentrasi optimum mampu memperlambat laju korosi pada logam, seperti aluminium. Penelitian ini menguji pengaruh ion silikat dalam larutan natrium klorida 3,5% terhadap laju korosi aluminium yang diuji dengan metode potensiostat dan dihitung dengan Ekstrapolasi Tafel. Pengaruh konsentrasi ion silikat terhadap laju korosi diamati pada variasi konsentrasinya yaitu 0, 25, 50, 75, dan 100 mM. Konsentrasi optimum natrium silikat untuk menurunkan laju korosi adalah 25 mM, laju korosi turun dari 0,0118 menjadi 0,0084 mm/tahun. Sebaliknya, penambahan konsentrasi natrium silikat hingga 100 mM, dapat meningkatkan laju korosi menjadi 0,101 mm/tahun.</span></span></p><p><span><span><span id="docs-internal-guid-17392559-7fff-0660-df12-7a65eee22bac"><span><strong>ABSTRACT. The Effect of Sodium Silicate Concentration on the Corrosion Rate of Aluminum Alloy in Sodium Chloride 3.5%.</strong> </span><span>Corrosion is a process of decreasing the quality of metals due to the reaction of metals with their environment. Seawater is one of the corrosive systems because of the high levels of chloride ions. Silicate ions with optimum concentrations can slow the rate of corrosion in metals, such as aluminum. This research examines the effect of silicate ions on the aluminum corrosion rate in a solution of sodium chloride 3.5%, tested by the potentiostat method and calculated by Tafel extrapolation. The effect of silicate ion concentration on the corrosion rate was observed in various concentrations of 0, 25, 50, 75, and 100 mM. The optimum concentration of sodium silicate in reducing the corrosion rate is 25 mM, in which the corrosion rate drops from 0.0118 to 0.0084 mm/year. Conversely, increasing the concentration of sodium silicate to 100 mM increased the corrosion rate to 0.101 mm/year.</span></span></span></span></p>

Effect of the deficiency of nitrate and silicate on the growth and composition of the benthic diatom Navicula incerta

Navicula incerta is a benthic diatom with potential use in nutrition and health for humans and aquaculture. Therefore, it is important to know its optimal growth conditions and biochemical composition. In this study, the effects of nitrate and silicate concentration on the growth kinetics and biochemical composition of N. incerta under laboratory conditions were measured. F/2 media was used as the control, and different concentrations of nitrogen (N/4, N/8 and N/16) and silicates (Si/4, Si/8 and Si/16) were evaluated. We measured cell concentration, chlorophyll-a and conducted proximal chemical analyses. It was found that different concentrations of nutrients affected the diatom’s growth kinetics and affected the concentrations of ash, chlorophyll, protein, lipids and carbohydrates. The highest concentration of lipids was obtained in the limiting treatment of nitrogen N/8 (27.09%), while the lowest value was found with silicate Si/8 media (16.97%). Carbohydrates increased compared to the control, with the N/16 treatment presenting the maximal concentration (23.31%). Treatments with reduced nitrate (N/8 and N/16) demonstrated the lowest concentrations of protein (18.75 and 12.44%, respectively), while in reduced silicate treatments, no statistical differences (P ≥ 0.05) were observed. Therefore, media limited nitrogen and silicates affected the growth kinetics and proximal chemical composition of N. incerta. The growth of this species using the N/8 medium is a suitable method for increasing lipid concentration in N. incerta.

ANALYSIS OF NITRATE CONCENTRATION, PHOSPHATE AND SILICATE RELATIONSHIP WITH THE ABUNDANCE OF PLANKTONIC DIATOMS IN MERAL WATERS, KARIMUN DISTRICT

Input of nutrients into the waters from various human activities (residential and industry) has the potential to cause changes in the physical, chemical and biological conditions of the waters. The study aims to determine the relationship of concentrations of nitrate, phosphate and silicate with the abundance of diatoms in the Meral waters. The method used is the survey method, the determination of the location of sampling is done by purposive sampling, data analysis (multiple regression). Based in the results of laboratory analysis nitrate concentrations ranged from 0,033 – 0,051mg/l, the phosphate concentration ranged from 0,076 – 0,086 mg/l, and silicate concentration ranged from 0,043 – 0,052 mg/l. The abundance of diatoms in Tanjung Tiram waters ranged from 90,3 – 208,3 ind/l. The results of statistical analysis of the relationship of nitrate, phosphate and silicate with the abundance of diatoms are expressed in terms of equation y = 58,460 + 904,562Nitrate – 251,562phosphate + 1573,489Silicate. This statement explains the concentration of nitrate, silicate positive (+) to the abundance of diatoms and phosphate related negative (-) to the abundance of diatoms. This condition shows that the nutrient concentration in these waters is relatively high so that it affects the abundance of diatoms.

Inhibition of Alga Contamination in Open-Culture Under Silicon Stress

Alga contamination was a major problem in microalgae open cultivation. The objective of this study was to estimate the effect of silicon on microalgae growth by mixed-culture experiments with four different microalgae. The results showed that under the osmotic pressure caused by high concentration of Na2SiO3, Navicula sp. N6 had a competition advantage of absorbing nutrient compared with the other three microalgae. The impacts (initial pH, nitrogen content, and silicon content) on cell growth and lipid accumulation were investigated by response surface analysis and the biomass and lipid content increased from 1.01 g/L and 10.98% to 1.33 g/L and 20.04% under the optimal conditions, with lipid yield raised from 110.90 mg/L to 266.53 mg/L. Comparison on the growth under optimum and silicon deficiency condition indicated that silicon played an important role on the growth of Navicula sp. N6 and algal contamination in diatom open scale cultivation could be solved by regulating the sodium silicate concentration.

Mechanism of silicate elution by hydrogen sulfide from bottom sediment in a brackish lake

Highly concentrated dissolved silicate was detected in pore water from anoxic-reducing sediment in Lake Nakaumi, a brackish lake. Silicate concentration also simultaneously increased with total hydrogen sulfide concentration during the summer. Generally, dissolved silicate is readily adsorbed onto ferric hydroxide and precipitates in an oxidative environment. In this study, we focused on the behavior of ferric hydroxide adsorbing silicate in sediment and determined that hydrogen sulfide was the main cause of dissolved silicate elution from ferric hydroxide adsorbing silicate because the hydrogen sulfide produced via microbiological processes in the anoxic-reducing environment was reducible for other metal oxides. According to laboratory experiments, silicate was released from ferric hydroxide by reacting with sodium sulfide, causing increasing elution of dissolved silicate from anoxic-reducing sediments with increasing concentration of sodium sulfide in the solutions. This result shows that hydrogen sulfide is very crucial for silicate release under a reducing environment. Therefore, in Lake Nakaumi, silicate would be released from the bottom after ferric hydroxide adsorbing silicate reacted with hydrogen sulfide in a summer reductive environment.

Quantitative Proteomic Analysis Reveals Novel Insights into Intracellular Silicate Stress-Responsive Mechanisms in the Diatom Skeletonema dohrnii

Diatoms are a successful group of marine phytoplankton that often thrives under adverse environmental stress conditions. Members of the Skeletonema genus are ecologically important which may subsist during silicate stress and form a dense bloom following higher silicate concentration. However, our understanding of diatoms’ underlying molecular mechanism involved in these intracellular silicate stress-responses are limited. Here an iTRAQ-based proteomic method was coupled with multiple physiological techniques to explore distinct cellular responses associated with oxidative stress in the diatom Skeletonema dohrnii to the silicate limitation. In total, 1768 proteins were detected; 594 proteins were identified as differentially expressed (greater than a two-fold change; p < 0.05). In Si-limited cells, downregulated proteins were mainly related to photosynthesis metabolism, light-harvesting complex, and oxidative phosphorylation, corresponding to inducing oxidative stress, and ROS accumulation. None of these responses were identified in Si-limited cells; in comparing with other literature, Si-stress cells showed that ATP-limited diatoms are unable to rely on photosynthesis, which will break down and reshuffle carbon metabolism to compensate for photosynthetic carbon fixation losses. Our findings have a good correlation with earlier reports and provides a new molecular level insight into the systematic intracellular responses employed by diatoms in response to silicate stress in the marine environment.