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Abstrak :
Nanopartikel perak (NPP) hasil biosintesis telah diketahui mampu mendeteksi keberadaan logam berat secara kolorimetri, namun belum cukup selektif karena menghasilkan perubahan warna yang serupa pada beberapa logam. Selain itu, stabilitas dari indikator kolorimetri berbasis NPP hasil biosintesis masih harus ditingkatkan. Telah diketahui bahwa modifikasi NPP dengan ligan berupa polimer dapat berfungsi sebagai penstabil sekaligus mempengaruhi agregasi antarpartikel dengan larutan analit yang dikenal sebagai sensor agregasi. Penelitian ini dilakukan untuk meningkatkan selektivitas dan stabilitas indikator kolorimetri keberadaan logam dan melakukan pengembangan pada NPP yang telah termodifikasi agar meningkat sensitivitasnya secara kolorimetri. Biosintesis NPP dilakukan dengan cara mereaksikan larutan AgNO3 1 mM dengan air rebusan daun kering bisbul (Diospyros discolor Willd.) dengan rasio 10:1 (v:v). NPP yang terbentuk dimodifikasi dengan larutan polivinil alkohol (PVA) 1% (b/v) dan 2% (b/v). Prosedur peningkatan sensitivitas dari indikator dilakukan dengan penambahan garam Natrium Klorida (NaCl) 1 M. Selektivitas terbaik didapatkan di larutan nanopartikel perak yang dimodifikasi dengan PVA 1% (b/v) dengan perubahan warna menjadi ungu muda secara selektif pada analit Cu2+. NPP termodifikasi PVA juga ditingkatkan sensitivitasnya dengan prosedur terpilih, yaitu dengan mereaksikan NPPtermodifikasi dengan NaCl 1 M pada rasio 10:2 (v:v), diaduk dengan pengaduk magnetik selama 15 menit, lalu langsung digunakan untuk pengujian pada analit. Larutan indikator terbukti mampu mendeteksi keberadaan ion Cu2+ hingga 0,1 ppm secara visual dengan LOD 0,459 ppm berdasarkan kurva regresi spektrofotometer UV-Vis. Percobaan dilakukan berdasarkan perbedaan warnanya dengan larutan blangko (tanpa ion Cu2+) serta spektrofotometer UV-Vis. Aplikasinya pada sampel, diujicoba menggunakan sampel makroalga merah (Kappaphycus alvarezii) dengan preparasi menggunakan metode destruksi basah. ......Silver nanoparticles, derived from biosynthesis method, have been known to detect heavy metals with colorimetry method, but their selectivity is not sufficient because they make similar changes in color to some metals. Besides, stability of colorimetric indicator, based on biosynthesized silver nanoparticles, still needed to be improved. It has been known that modification of silver nanoparticles with ligand, such as polymers, can be functioned as stabilizer and affects aggregation between particles and analyte solution. This research was conducted to improve the selectivity of colorimetric indicator for metals in analyte solution and to implement the development of modified silver nanoparticles to improve their sensitivity in colorimetry method. Biosynthesis of silver nanoparticles was conducted by reaction of AgNO3 1 mM solution with boiled water of velvet apple (Diospyros discolor Willd.) leaves in 10:1 (v:v) ratio. Then, silver nanoparticles are modified with polyvinyl alcohol (PVA) 1% (w/v) and 2% (w/v). Procedures to improve the sensitivity of indicator was conducted by addition of sodium chloride (NaCl) 1 M. Best selectivity was reached in silver nanoparticles solution that modified with PVA 1% (w/v) based on selective changes in color of Cu2+ analytes. Modified-silver nanoparticles? sensitivity has also been improved by chosen procedure, which is by reacted modified-silver nanoparticles with NaCl 1 M in 10:2 (v:v) ratio, stirred by magnetic stirrer in 15 minutes, then directly used to examine analyte solution. The indicator solution also has been proven that was able to detect Cu2+ ions up to 0,1 ppm as lowest concentration, and with LOD 0,459 ppm based on spectrophotometer UV-Vis. This test based on comparison with blank solution (without Cu2+ ions) and UV-Vis spectrophotometer in trial with red macroalga (Kappaphycus alvarezii) sample, which is prepared by wet destruction method.

Abstrak :
This study aims to analyze the effect of chemical pretreatment using sodium hydroxide (NaOH) on the capacity of coco peat in removing of copper (11) ions from aqueous solutions. The effects of varying the molarity of NaOH, the solution pH, initial Cu(II) concentration, coco peat dosage and contact time were studied in batch experiment. The result of the preliminary pretreatment study shows that treatment with 0.5M NaOH greatly enhanced the metal sorption capacity of raw coco peat. The uptake capacity for Cu of the raw coco peat was increased from 46% to 83% at pH 4.0 and from 15% to 27% uptake for initial solution pH of 2.4. The results showed that the removal rate is directly proportional to pH, coco peat’s dosage and contact time and inversely proportional to Cu(Il) concentration. The adsorption process is best explained by the Langmuir isotherm than the Freundlich isotherm, indicating monolayer adsorption on a homogenous surface. The rate of reaction follows the pseudo-second order kinetic model, signifying that chemisorption is the rate limiting mechanism. The results of the Fourier Transform Infra-Red (FTIR) analysis indicated that the main functional groups involved in the sorption of copper to NaOH pretreated coco peat are the hydroxyl, carboxyl and phenolic groups. Based on the results of this study, it was found that pretreating coco peat with NaOH significantly improve the overall efficiency of coco peat in removing Cu(II) by adsorption process.