1,720,961 research outputs found
Ekstraksi Pb2+ Menggunakan Fasa Padat Silika Abu Sekam Padi - Kitosan
No full textTimbal merupakan logam berat yang memiliki toksisitas tinggi apabila masuk ke tubuh manusia. Hal ini ditunjukkan dengan nilai LD Pb yaitu 500 mg/kg berat badan. Peraturan Pemerintah No. 82 Tahun 2001 menyebutkan bahwa konsentrasi maksimum Pb 2+ yang diijinkan di perairan adalah 0,03 ppm. Kadar Pb 2+ di perairan dapat dikurangi dengan beberapa metode yaitu elektroplating, oksidasi, reduksi, dan pemisahan menggunakan membran. Namun, metode ini kurang efektif karena membutuhkan biaya yang tinggi serta menghasilkan buangan yang banyak. Oleh karena itu, metode ekstraksi fasa padat digunakan pada penelitian ini karena metode ini cukup sederhana sekaligus dapat dilakukan pemekatan konsentrasi Pb 2+ sehingga kesulitan pengukuran dapat teratasi.
Tujuan penelitian ini adalah untuk mengetahui pengaruh komposisi fasa padat silika – kitosan, mempelajari interaksi Pb 2+ dengan silika – kitosan, serta mengetahui pengaruh konsentrasi Pb 2+ dan asam sitrat pada ekstraksi Pb 2+ . Untuk mencapai tujuan tersebut, maka dilakukan isolasi silika dari abu sekam padi sehingga dapat digunakan sebagai fasa padat. Silika dimodifikasi menggunakan kitosan untuk memperbesar luas permukaan fasa padat agar adsorpsi Pb 2+ dapat terjadi secara maksimal. Optimasi komposisi silika : kitosan dilakukan agar jumlah Pb 2+ yang teradsorpsi maksimal. Pengaruh konsentrasi Pb 2+ dan asam sitrat dipelajari untuk memperoleh recovery Pb 2+ optimum. Interaksi elektrostatik antara ion Pb 2+ dengan fasa padat silika – kitosan dapat diperkirakan berdasarkan hasil penelitian yang telah dilakukan.
Hasil penelitian menunjukkan bahwa komposisi optimum silika : kitosan adalah silika-kitosan 65%. Pada komposisi ini, KTK dan kapasitas adsorpsi yang diperoleh adalah 0,455 mek/g dan 9,715 mg/g. Recovery Pb 2+ sebesar 81,18% tercapai pada saat elusi menggunakan asam sitrat 0,05 M. Hasil ini menunjukkan bahwa fasa padat silika – kitosan dapat digunakan sebagai metode alternatif untuk pemekatan dan penentuan kadar Pb 2+ yang rendah di perairan
Preparation of Methanyl Yellow Test Strip Based on Nata De Coco Membrane Immobilized Anthocyanin Extracted from Rosella Flower (Hibiscus Sabdariffa L.)
No full textMethanyl yellow is a synthetic dye used in the textile industry and its use is prohibited in food products. Its abuse is still found in crackers, noodles, tofu, and beverages. Methanyl yellow identification test used color reaction test, thin layer chromatography, paper chromatography, TLC scanner, and UV-Vis spectrophotometry. So, in this study, the methanyl yellow test strip test method was developed using anthocyanin immobilized nata de coco membrane with rosella flower extract. The purpose of this study was to determine the selectivity and sensitivity of the resulting test strips. The test strip consisted of nata de coco membrane and rosella flower extract reagent. The test strip made has an optimum contact time of 10 seconds. In the analysis using FTIR, the functional groups O–H, C–H alkanes, C=O, C=C alkenes, C–O, and C–H alkenes on the test strip indicated anthocyanin compounds. In the test strip which was reacted with methanyl yellow the functional group identified had a weaker absorption than the test strip which had not been reacted. The characterization test includes a detection limit test with detection capability starting at a concentration of 6 ppm and lifetime test results, up to the 21st day the strip test can be used, storage using dark bottles is better than clear bottles. So that the resulting test strips provide good data and can be used for quick measurements
Preparation of Methanyl Yellow Test Strip Based on Nata De Coco Membrane Immobilized Anthocyanin Extracted from Rosella Flower (Hibiscus Sabdariffa L.)
No full textMethanyl yellow is a synthetic dye used in the textile industry and its use is prohibited in food products. Its abuse is still found in crackers, noodles, tofu, and beverages. Methanyl yellow identification test used color reaction test, thin layer chromatography, paper chromatography, TLC scanner, and UV-Vis spectrophotometry. So, in this study, the methanyl yellow test strip test method was developed using anthocyanin immobilized nata de coco membrane with rosella flower extract. The purpose of this study was to determine the selectivity and sensitivity of the resulting test strips. The test strip consisted of nata de coco membrane and rosella flower extract reagent. The test strip made has an optimum contact time of 10 seconds. In the analysis using FTIR, the functional groups O–H, C–H alkanes, C=O, C=C alkenes, C–O, and C–H alkenes on the test strip indicated anthocyanin compounds. In the test strip which was reacted with methanyl yellow the functional group identified had a weaker absorption than the test strip which had not been reacted. The characterization test includes a detection limit test with detection capability starting at a concentration of 6 ppm and lifetime test results, up to the 21st day the strip test can be used, storage using dark bottles is better than clear bottles. So that the resulting test strips provide good data and can be used for quick measurements
Komparasi Daya Adsorpsi Silika Dari Abu Sekam Padi dan Ampas Tebu Terhadap Adsorpsi Pb2+
Full text linkHeavy metals are the main pollutants which numbers are increasing . PB is a heavy metal that has high toxicity when it enters the human body. This is indicated by the LD value of 50 Pb which is 500 mg / kg body weight. Based on Government Regulation No. 82 of 2001, the maximum permissible concentration of Pb2 + in waters is 0.03 mg / L. Therefore, the presence of Pb2 + in the waters needs to be controlled so that pollution in the waters can be reduced. The purpose of this study was to determine the silica adsorption capacity of rice husks and sugarcane bagasse against Pb2 + adsorption. In this study the characterization of each adsorbent was carried out to determine the active functional groups in the bonds that occur. The maximum adsorption capacity of Pb (II) in Si-husk is 126 mg / g at 0.6 g of mass of the adsorbent while the maximum adsorption capacity of Pb (II) in Si-sugarcane is 109.69 mg / g at 0.8 g of adsorbent
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
The Effect of Contact Time of Javabark Adsorbent (Lannea coromandelica ( houtt.)merr) on Cd (II) Adsorption Capacity
Full text linkAccording to Indonesian Minister of Health Regulation No. 2 of 2023, the maximum limit for cadmium in bottled water is 0.003 mg/L. In this study, tannin biosorbents were used from the extraction of Javanese bark. Javanese bark contains tannin compounds that have the potential to bind heavy metals. This study aims to determine the effect of varying contact times of Java wood bark biosorbent on the adsorption capacity of Cd (II). The method used is an experiment to study the effect of contact time of Java wood bark biosorbent on the adsorbate. The contact times used for the Java wood bark biosorbent were 20, 40, 60, 80, 100, 120, 140, and 160 minutes. The residual Cd (II) concentration in the solution was determined using a UV-Vis spectrophotometer. The adsorption capacity of Cd (II) at contact times of 20, 40, 60, 80, 100, 120, 140, and 160 minutes was 0.073; 0.075; 0.078; 0.079; 0.116; 0.060, 0.052; 0.035 mg/g. From the results of the study, it can be concluded that the longer the contact time of the biosorbent in the adsorption of Cd (II) metal, the adsorption capacity will increase until it reaches the optimal contact time. After reaching the optimal contact time, adsorption decreases due to the desorption process. In this study, the optimal contact time for Java wood bark biosorbent was obtained at 100 minutes with an adsorption capacity of 0.116 mg/g.
Keywords:Tannin;Cadmium;Adsorption;Biosorbent;Javabark
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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