The rapid development of information and communication technology provides an opportunity for scientists to develop a quantitative analytical method that is built on a mobile gadget as a detector. In this paper, we report a low-cost, simple and portable analytical method for mercury ion quantification based on digital image colorimetry coupled with a smartphone application. A small amount of silver nanoparticles (AgNPs) was used as a colorimetric agent that is selective only to mercury ions. The yellowish brown color of AgNPs instantly changed to colorless after the addition of mercury ions due to a redox reaction. To increase the portability, we attached the AgNPs onto a medium to create a paper-based analytical device. The final data processing of the colorimetric analysis was conducted using an android application available on the Google Play Store, called "Mercury Detector". The proposed method has good sensitivity, with a detection limit of 0.86 ppb, which is comparable to those of bulk and more expensive instruments. This allows for the detection of mercury ions as low as 2 ppb (10 nM), which is also the maximum contaminant level permitted in drinking water by the US Environmental Protection Agency. The proposed method was applied to real samples that provide satisfactory results on accuracy (2.4%) and precision (2.5%).
Beach sand is an abundant natural resource that contains silica minerals with many benefits. One of the uses of silica is to remove synthetic dyes that are toxic to biota in the environment. The goal of this research was to extract and characterize the silica from Bengkulu beach sand and to apply it as dyes adsorbent. The extraction of silica consisted of two steps that were potassium silicate formation and gel formation. The gel was formed by adding strong acid into a potassium silicate solution. Silica's particle size and crystallinity were characterized using PSA and XRD, respectively. SEM-EDS was used to characterize the morphology and chemical composition of extracted silica. The effect of the different experimental settings, like pH, temperature, contact time, the concentration of dyes and adsorbent weight, on adsorption of dyes were monitored as well as the study of adsorption isotherms, kinetics, and thermodynamics. At equilibrium, synthetic dyes adsorption to silica suited to the Freundlich model producing correlation coefficients (R 2 ) of 0.853 and 0.976 for remazol blue and congo red, respectively. At optimum conditions, maximum adsorption capacities for remazol blue and congo red were 133 and 131 mg/g, respectively. The research implied that adsorption of dyes to silica fitted the pseudo-second-order model with thermodynamic values of ∆G°, ∆H°, and ∆S° were -4.04 to 2.19 kJ/mol, -13.53 to -4.726 kJ/mol, and 0.019 to 0.021 J/mol.K, respectively. By using these results, we resolve that the adsorption of dyes trends was exothermic and spontaneous. In addition, the reaction increases the system's entropy. This study emphasizes the potential of silica from the sand beach as a substitute economical adsorbent for the toxic dyes removal.
The goal of this research was to make silver nanoparticles (NPP) with a cherry fruit extract bioreductor which was used for mercury metal analysis by using a digital image method. The process of making silver nanoparticles had done by a bottom up method involving a reduction reaction. The precursors used were 1 mM AgNO3 solution and as a bioreductor was an antioxidant compound which were in cherry fruit extract. Variation of the volume ratio between cherry fruit extract and 1 mM AgNO3 solution was 1: 3, 1: 4, 1: 5, 1: 6, and 1: 7 and the variation of contact time were 5, 15, 30, 45, 1, 2, 3 hours, and 1, 2, 7 days. The most optimum results of silver nanoparticles were synthesized with 1 : 4 volume ratio and 1 hour contact time. From the results of selectivity test, it was known that silver nanoparticles were made selective toward Hg and Fe metal. The sensitivity test toward Hg metal, it was known that NPP can detect mercury metal with the smallest concentration of 16,7 ppb.
ABSTRAKPenelitian ini bertujuan untuk mengembangkan media pembelajaran dalam bentuk video pembelajaran kimia dan digunakan untuk mengukur kemampuan berpikir kritis siswa. Metode yang digunakan adalah penelitian dan pengembangan (Research and Development) pembelajaran kimia pada bahan minyak bumi dengan model Dick dan Carey, melalui tahapan: desain, validasi, revisi dan tes formatif untuk siswa kelas XI di SMAN 1 Bengkulu Tengah. Kemampuan berpikir kognitif siswa dapat diukur dan dilihat dari hasil tes formatif, data yang diperoleh dalam bentuk data kuantitatif dan dilakukan analisis deskriptif untuk menilai kemampuan berpikir kritis siswa. Berdasarkan hasil tes formatif, 13,3% siswa kurang kritis, 60% siswa kritis, 20% siswa kritis dan 6,67% sangat penting. Kata kunci: Pengembangan; media; pembelajaran kimia; video; berfikir kritis. 0% 13,3 % 60% 20% 6,67%
[SYNTHESIS AND CHARACTERIZATION OF XEROGEL RESULTS OF COPRECIPITATION OF LONG BEACH BENGKULU BEACH]. This research aims to synthesize and characterization to Xerogel which synthesizes from Pantai Panjang sands Bengkulu. The method used for this study to synthesizes Xerogel is to use the coprecipitation method. Qualitative XRF test against raw sand materials that were used show that the content of the element is the most significant element of Si. The first stages of the synthesis of Xerogel is a purification of the sand sample.. Xerogel synthesis is carried out in two phases, namely the manufacture of aqueous solutions of Sodium Silicate and continued with the formation of a gel. The production of Sodium Silicate solution is done using the NaOH concentration at 5, 6 and 7 M. Gel formation process is done by adding a solution of HCl 10 M into the solution of Sodium Silicate, followed by process of filtration, washing and drying in the oven. The results showed that the optimum conditions of synthesis of Xerogel obtained using 6 M NaOH , with a yield obtained is amounting at 0.8%. The results of the test by XRD shows that the silica crystal structure on Xerogel are amorphous-shaped. SEM-EDS test results show that the acquired Xerogel on research has a smooth texture and size is not homogeneous with the highest content of elements are the elements Si and O. PSA test shows that particle size in Xerogel an average at 191.4 nm.
This perpose of this research was to know the isotherm, kinetics and thermodynamics adsorption of synthetic dye onto activated carcoal from palm oil shell. The synthetic dye were Reactive Red and Direct Blue. The model of isotherm were Langmuir and Freundlich, kinetics adsorption tested were Pseudo orde-1 and Pseudo orde-2, and also thermodynamics were free energy change (?Go), enthalpy change (?Ho), and entropy change (?So). The dominant isotherm adsorption was isotherm Freundlich, kinetic adsorption Pseudo 2 th order with the value (?So), (?Go) and (?Ho), Reactive Red were 0,0028 Kj/mol.K , -3,93 Kj/mol, and -36,12 Kj/mol respectively. Whereas in direct blue were 0,0034 Kj/mol.K, -1,67 Kj/mol,and -30,16 Kj/mol respectively.
This study aimed to compare the chemistry learning outcomes of students with using word square model learning and scramble model learning in grade X MAN 2 Kota Bengkulu on the subject of chemistry compound nomenclature. This was quasy experimental research and held in March to May 2018. Population in this study is the entire class X MIA in MAN 2 Kota Bengkulu 2017/2018 academic year, amounting to 149 students. Sample is class X MIA 1 and class X MIA 3. The sample of the research is class X MIA 1 with 32 students and class X MIA 3 with 33 students. Data analysis used normality test, homogeneity test and hypothesis test (t test). Data analysis was performed using Statistical Package for The Social Science (SPSS) version 16.Improvement student’s learning outcomes in this research was taken from difference assess of pretest and posttest. At experiment class of I average value improvement of student’s learning outcomes was 50.32. while at experiment class of II, average value improvement of student’s learning outcomes was 44.4 . through some statistic test, there was t-test (? = 0.05) which done test the hypothesis to obtained the test result was t value = 2.174 and t tabel = 1.998. The result of data analysis showed that were significant differences in student learning outcomes between the class which implemented word square model learning and the class which implemented scramble model learning. Student learning outcomes that apply the word square model of learning better than student learning outcomes that apply the scramble model of learning.
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