Jurnal Akademika Kimia
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Atmospheric Corrosion Inhibition of Steel Using Tea Leaf Extract in the Coastal Environment of Air Tawar, Padang
Get PDFThis study evaluates the effectiveness of tea leaf extract as a corrosion inhibitor for steel under real coastal atmospheric exposure. The novelty of this work lies in its direct assessment of a plant-derived inhibitor in an open-air marine environment, a setting that has not been adequately addressed in previous studies, which have largely focused on controlled aqueous systems. In addition, this study employs mature tea leaves, an abundant agricultural byproduct with naturally high tannin content, processed through a simple, solvent-free extraction method, thereby offering a sustainable route for green inhibitor development. The extract was obtained from mature tea leaves through aqueous boiling, and its tannin content was quantified using UV–Vis spectrophotometry. ASSAB 760 steel specimens were coated by immersion in tea extract at varying concentrations and soaking durations, followed by natural exposure in a coastal environment for 1 to 30 days. Corrosion behavior was evaluated using the weight loss method. The results showed that mature tea leaves contained the highest tannin concentration (29530.95 ppm), supporting their selection for inhibitor application. The optimum extract concentration was identified as 11000 ppm with a 5-hour immersion time. Under these conditions, treated steel exhibited a substantially lower corrosion rate (7.78 × 10⁻⁵ g/cm²/day) compared to untreated steel (1.66 × 10⁻⁴ g/cm²/day), corresponding to a maximum inhibition efficiency of 84.71%. The inhibition mechanism is attributed to the formation of a stable Fe³⁺–tannin chelate complex that adsorbs onto the steel surface, forming a protective film that restricts the ingress of aggressive chloride-rich moisture in the coastal atmosphere. Overall, the findings demonstrate the practical viability of mature tea leaf extract as an effective and environmentally benign atmospheric corrosion inhibitor, providing field-relevant insight into sustainable protection strategies for marine-exposed steel infrastructure
Application of Discovery Learning Model to Improve Student Science Process Skills in Colloid Material on Senior High School
Get PDFThis study aimed to describe the improvement of students' science skills by applying the discovery learning model to the colloid material of class XI IPA SMA Negeri 1 Ampibabo. The research method used was pre-experiment with one group pretest-posttest. The sample in this study consisted of students from class XI IPA as experimental class 1, which was planned for 30 students, and class XI IPA B as class experiment 2, which meant 30 students. The instrument used was a science skills test, student activity observation sheets measured using six aspects, namely, observation, asking questions, hypothesizing, classification, interpreting data, and communicating) and student response questionnaires. The results of the study were obtained from the science skills test scores, the pretest, and the hottest of the two classes; namely, the average pretest score for class XI IPA A was 11.66 % and class XI IPA B was 13.3 %, while the average posttest score was 11.66 %. Obtained from class XI IPA B of 75.48% and class XI IPA B of 75.97 % The results of the analysis of the six aspects of science process skills of students in class XI IPA A obtained an average of 75.52 % and class XI IPA B was obtained an average of 78.64 %. Based on the study results, it can be ignored that the application of discovery learning models can improve students' skills in colloid material in class XI IPA SMA Negeri 1 Ampibabo. This can be seen from the proportion of the average student response, which is 90.61 % strongly agree with the discovery learning model
Analysis of Differentiated Learning Implementation Using a 3D Chemistry Periodic Table Application to Improve Students' Cognitive Ability
Get PDFThe cognitive ability of each student is different. To improve it, it needs to be trained and optimized. The purpose of cognitive skills is the implementation of differentiated learning using a 3D Chemistry Periodic Table Application to improve the students’ cognitive ability. This research was implemented in the even semester academic year 2023 / 2024 at State Senior High School 1 Tambang. The method used in this research was mixed-method research with a research design Sequential Explanatory model, with research samples consisting of three classes of Grade X at State Senior High School 1 Tambang, namely two (2) experimental classes and one (1) control class. The post-test research result showed a significance of 0.000 < 0.05 until indicating a significant difference between the experimental and control classes. Besides, the average N-Gain of the experimental class namely 0.77, and the second experimental class was 0.71, with high category, and the control class was 0.60, with medium category. In other words, it is proven that differentiated learning with a 3D application increases cognitive ability. The students’ response after gaining the learning by using 3D was excellent, with a percentage of 81.41 %. The results of this research are expected to help teachers improve the students’ cognitive abilities
Determination of Total Flavonoid Content in Local Sakura Leaf Extract or Small Bungur (Lagerstroemia indica L.)
Get PDFThe small bungur plant (Lagerstroemia indica L.) is one of the plants with potential as a medicinal plant. Almost all parts of this plant can be used, namely the leaves, stems, fruit and roots. Bungur leaves can be used for skin diseases, leaf powder for malaria, and decoction of old leaves for diabetes. Bungur leaves contain chemical compounds, one of which is flavonoids. This study aims to determine the total flavonoid content of extracts from young and old leaves of local cherry blossoms (small bungur), using UV-Vis spectrophotometry. The extraction method used was multistage maceration using three different solvents: hexane (nonpolar), ethyl acetate (semipolar), and methanol (polar). The results showed that the average total flavonoid content of young leaf extracts and old leaves of small bungur, measured by UV-Vis spectrophotometry at a maximum wavelength of 410 nm, was 8.810 mg/100g and 7.301 mg/100g, respectively. Among the three solvents used, extracts of young and old leaves of small bungur using hexane and ethyl acetate do not contain flavonoids, whereas extracts of young and old leaves of small bungur using methanol do
Study of Ethanol Extract of Karamunting (Rhodomyrtus tomentosa (Aiton) Hassk) as Acid-Base Bioindicator
Get PDFKaramunting or Rhodomyrtus tomentosa (Aiton) Hassk is a fruit that contains anthocyanins. This study aimed to determine the potential of the ethanol extract of this fruit as an acid-base bioindicator. Karamuting fruit was macerated using three solvents (n-hexane, ethyl acetate, and ethanol) for 24 hours. The extract of the karamunting fruit was tested as indicators in acid-base solutions and buffer solutions and compared with phenolphthalein and methyl orange for acid-base titrations, namely: Strong acids with strong bases, weak acids with strong bases and weak bases with strong acids. The results showed that the ethanol extract of karamunting fruit was brown, in strong acids was red, in strong bases was dark green, in weak acids was pink, and in weak bases was light green. Furthermore, the kara munting fruit indicator extract buffer solution gave four groups of colour changes, namely, at pH 1, it was red; at pH 2 to 6, it was pink; at pH 7 to pH 10, it was light green; and at pH 11 to 12, it was dark green. The ethanol extract of karamunting fruit can be used as an acid-base indicator because it gives equivalent results to comparative indicators, namely phenolphthalein and methyl orange
Soybean Tempeh: Effect of Yeast Concentration and Fermentation Duration on Organoleptic Test as a Learning Resource
Get PDFTempeh is a traditional Indonesian fermented food known for its high nutritional value. This study sought to assess the impact of yeast concentration and fermentation length on moisture content, protein content, and organoleptic evaluation of yellow soybean tempeh sourced from Tojo Una-Una, Poso, and Palu. The research included a 3 × 3 factorial design incorporating yeast concentrations of 1, 2, and 3 grams, alongside fermentation durations of 30, 48, and 72 hours. The moisture content was assessed using the gravimetric method, the protein content was determined via the Kjeldahl method, and 20 panelists performed an organoleptic evaluation. The findings indicated that the moisture content of tempeh generally rose with prolonged fermentation time and elevated yeast concentration. The maximum moisture content, 63.22%, was observed in tempeh from Tojo Una-Una, which used 2 grams of yeast and had a fermentation duration of 72 hours. The minimum value, 50.18%, was also from Tojo Una-Una with 1 gram of yeast and 30 hours of fermentation. Protein levels peaked at 48 hours of fermentation with 3 grams of yeast, reaching a maximum of 26.88% in the Palu area. In contrast, the minimum was recorded at 18.55% in tempeh from Tojo Una-Una with 2 grams of yeast and 30 hours of fermentation. The organoleptic test results indicated that panelists favored Poso tempeh in terms of flavor, aroma, and texture. The concentration of yeast and the time of fermentation influence the moisture content, protein content, and organoleptic quality of tempeh. The methodologies and findings of this study serve as a resource for chemistry education in the format of LKPD
The Influence of The STEM Learning Model on Improving Students' Scientific Literacy and Numeracy Skills on Reaction Rate Material
Get PDFThis study was conducted to determine whether the STEM learning model has a significant effect on students' scientific literacy and numeracy skills at the rate of material speed. The target population was grade XI students of SMA Negeri 3 Medan (consisting of 9 classes), and two classes were selected as samples through purposive sampling techniques. The type of research used was quasi-experimental (pseudo-research), with a Control Group Pretest-Posttest Design. The data collection instrument was a multiple-choice test (20 questions) designed to measure scientific literacy and numeracy, and has been tested for validity and reliability. Data analysis employed a one-tailed t-test (right-tailed) with a significance level of 0.05. The results of the statistical analysis showed that the t-count value (7.367) was greater than the t-table value (1.688), leading to the rejection of the null hypothesis (H0) and the acceptance of the alternative hypothesis (Ha). In conclusion, the STEM learning model has a significant impact on enhancing students' scientific literacy and numeracy skills in the context of reaction rates
Optimization of Palm Bunch Ash-Based Catalysts for the Transesterification of Waste Cooking Oil into Biodiesel
Get PDFThe increasing dependence on fossil fuels to meet fuel needs has caused several problems, such as air pollution, greenhouse effects, unpleasant odors, and loud noises. This research aims to design an alternative fuel in the form of biodiesel by applying a heterogeneous catalyst based on palm bunch to synthesize biodiesel through transesterification. The research stages include activating the active sites of palm bunches through calcination at temperatures of 400 °C, 500 °C, and 600 °C; refining waste cooking oil; esterification; and transesterification. The active components of palm bunch ash (PBA) were characterized using XRF and alkalinity testing. XRF results indicated that PBA contains active basic compounds such as K₂O and CaO, crucial in catalytic activity. Physical-chemical property testing revealed that the synthesis achieved the highest yield of 93.744 %. The results of the physical-chemical characteristic tests produced the best density with an average of 0.888 g mL⁻¹, and the lowest viscosity with an average of 3.79 cSt at 40 °C with an iodine number of 80.116 g I₂ 100 g⁻¹, a saponification number of 170.57 mg KOH g⁻¹, and a refractive index of 1.445. The catalyst demonstrated stable performance up to three reuses with yields ranging from 80–90 %. FTIR spectra showed strong absorption bands at 1172–1165 cm⁻¹, indicating C-O-CH₃ stretching from methyl esters. GC-MS analysis showed that the biodiesel consists of various fatty acid methyl esters (FAME), with the main component being methyl oleate, which appears at a retention time of 37.096 minutes with an area of 40.31 %. So it is shown that PBA catalysts have an excellent potential for commercial applications as they can reduce dependence on fossil fuels by utilizing household waste
The Implementation of Project-Based Worksheets for Making Taro Tape with Dragon Fruit Peel to Develop Students’ Psychomotor Skills
Get PDFDeveloping students’ psychomotor skills is insufficient through theoretical learning in the classroom alone. Still, it must be supported by contextual, practical activities, such as fermenting taro tape with dragon fruit peel, through the application of project-based worksheets. This study aims to analyze students’ ability to complete project-based worksheets and the development of students’ psychomotor skills through testing the characteristics of taro tape. The method employed was a pre-experimental design with a one-shot case study involving tenth-grade students at a senior high school in Bandung City as the research subjects. The assessment instruments included a six-stage project-based worksheet, psychomotor tests covering three characteristics, and product and presentation assessments with eight and six aspects, respectively. Project-based worksheets were implemented in several stages: identifying problems, designing projects, conducting experiments, developing prototypes, evaluating products, and finalizing. The study’s results showed that students’ ability to complete project-based worksheets achieved an average score of 92, categorized as very good. The ability to complete project-based worksheets in the product evaluation stage received the highest score of 100, while the experimentation and prototype development stages received the lowest score of 88. Additionally, the development of students’ psychomotor skills, as measured by the Taro Tape Characteristic Test, showed an average score of 95, categorized as very good. Psychomotor skills in organoleptic tests received the highest score of 100, while the TAT test received the lowest score of 85. Implementing project-based worksheets proved effective in developing students’ psychomotor skills through the stages of project-based learning. These findings underscore the importance of using project-based worksheets as a contextual learning approach that supports chemistry education and fosters active student engagement in developing psychomotor skills
Determination of the Content of Nitrogen (N), Phosphorus (P), and Potassium (K) in Pellets from Cakalang fish (Katsuwonus pelamis) Waste Fermented Using Adhesives From Broiler Chicken Feces
Get PDFFish offal and broiler faeces are underutilised organic waste; the purpose of this study was to determine the levels of nitrogen (N), phosphorus (P) and potassium (K) contained in the pellets from cakalang fish (Katsuwonus pelamis) waste fermented using adhesive from broiler chicken faeces. Nitrogen levels were determined using a colourimeter, phosphorus levels were determined using a UV-Vis spectrophotometer, and potassium levels were determined using a flame photometer. The results showed that the analysis of nitrogen, phosphorus, and potassium in the pellets from the fermentation of cakalang fish waste obtained an average of 4.2 %, 2.21 %, and 3.85 %, respectively