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Roto Roto

Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada, Sekip Utara, Yogyakarta 55281, Indonesia

Author-ID : 3959868

Chemical Engineering, Chemistry & Bioengineering Chemistry

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Articles

Modified Silica Adsorbent from Volcanic Ash for Cr(VI) Anionic Removal Endang Tri Wahyuni; Roto Roto; Firda Ainun Nissa; Mudasir Mudasir; Nurul Hidayat Aprilita
Indonesian Journal of Chemistry Vol 18, No 3 (2018)
Publisher : Universitas Gadjah Mada

In the present research, cetyltrymethyl ammonium bromide (CTAB)-modified silica from Kelud’s volcanic ash has been prepared and examined as adsorbent for removal of the hazardous Cr(VI) anion. The research was initiated with purification of SiO2 from the volcanic ash that was carried out by reacting the volcanic ash with NaOH powder at 900 °C for 2 h, followed by dissolving the ash to water at 100 °C, and then was acidified with HCl 1 M to form hydrogel. By calcination of the hydrogel, silica (SiO2) gel was obtained. The next step was modification of the silica with CTAB, that was performed by interacting the CTAB solution with the gel, in which the concentration of the CTAB was varied. Then the CTAB-modified silica samples were characterized by using FTIR, XRD, and SEM machines. The activity of the adsorbent was examined for adsorption of CrO4= in the solution. The results of the research demonstrate that the amorphous silica gel and the amorphous CTAB-modified silica have been obtained. The CTAB-modified silica was found to possess much higher ability in the adsorption of CrO4= anion, that was 48.90 mg/g, compared to that of the unmodified silica gel, as much 5.68 mg/g. These findings strongly prove that the negative surface of the CTAB-modified silica adsorbent has been successfully formed. Furthermore, it is also observed that increasing concentration of CTAB in SiO2-CTA can promote more effective adsorption of the CrO4= from the solution, but the further enlargement of the CTAB concentration leads to the adsorption decreased, and the highest adsorption was shown by CTAB-modified silica prepared with 0.10 mole of CTAB/1 mole SiO2.

Effect of Reducing Agents on Physical and Chemical Properties of Silver Nanoparticles Roto Roto; Hani Prima Rasydta; Adhitasari Suratman; Nurul Hidayat Aprilita
Indonesian Journal of Chemistry Vol 18, No 4 (2018)
Publisher : Universitas Gadjah Mada

Silver nanoparticles having uniform size and shape, a diameter range of 10–50 nm, excellent stability, and high zeta potential are always desirable for many applications. The silver nanoparticles were synthesized by chemical reduction method using some reducing agents in a polyvinyl alcohol solution. This study aims at determining the effect of reducing agents on the chemical and physical properties of silver nanoparticles. Ascorbic acid, sodium borohydride, hydrazine, sodium citrate, and glucose were used as reducing agents. Surface Plasmon Resonance (SPR) absorbance, morphology, zeta potential, crystal system, and stability of the products were studied. The results showed that the chemical and physical properties of the colloidal Ag nanoparticles were dependent on the reducing agents. In general, the produced silver nanoparticles have an fcc crystal system with a unit cell of 4.0906–4.0992 Å. The SPR absorbance of the colloids has the peak in the range of 401–433 nm. We found that the colloid of silver nanoparticles prepared by using ascorbic acid has uniform spherical shape, the diameter of about 20 nm, and zeta potential of -10.4 mV. After being stored for one month, the SPR absorbance of the colloid decreased by only 5%. This type of colloidal Ag nanoparticles prepared by using ascorbic acid is expected to be used for chemical sensors, an antibacterial agent, and so on.

Investigation on the Effect of Addition of Fe3+ Ion into the Colloidal AgNPs in PVA Solution and Understanding Its Reaction Mechanism Roto Roto; Marcelina Marcelina; Nurul Hidayat Aprilita; Mudasir Mudasir; Taufik Abdillah Natsir; Bella Mellisani
Indonesian Journal of Chemistry Vol 17, No 3 (2017)
Publisher : Universitas Gadjah Mada

Analysis of Fe3+ ion present in aqueous solutions is always of interests. Recently, this ion has been analyzed by colorimetric methods using colloid of silver nanoparticles (AgNPs) in capping agents of polymers. The reaction mechanism between AgNPs and Fe3+ is still subject to the further investigation. In this work, 1,10-phenanthroline was used to probe the reaction mechanism between AgNPs and Fe3+ ion in the solution. The colloids of AgNPs were prepared in the polyvinyl alcohol (PVA) solution and reacted with Fe3+. The colloid surface plasmon absorbance decreases linearly along with the increase in Fe3+ concentration. The addition of 1,10-phenanthroline to mixture changes the solution to red, indicating that the reaction produces Fe2+. This suggests that the reduction of the AgNPs absorbance is the result of oxidation of the Ag nanoparticles along with the reduction of Fe3+.

Assessment of Multi-Nutrients and Heavy Metals in Inorganic Fertilizers Widely Used by Indonesian Farmers Using NAA Sri Murniasih; Sri Juari Santosa; Roto Roto
Indonesian Journal of Chemistry Vol 22, No 3 (2022)
Publisher : Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/ijc.69908

This research aims to determine the concentration of multi-nutrients and heavy metals and investigate the correlation among them in the seven inorganic fertilizers in Indonesia. Sample analysis was carried out using the NAA method. The highest concentrations of macro-nutrients were K (36.54 %) and Cl (18.09%) found in the KCl sample, while Ca (23.01%) was observed in the TSP sample. In the case of micro-nutrients, the highest concentrations of Se (0.36 mg/kg), Ti (597 mg/kg), Br (1.84%), and Ni (2.46 mg/kg) detected in the NPK sample. Meanwhile, the highest concentrations of Co (19.57 mg/kg) and Na (1.40%) were measured in the ZA sample, while Mg, with the highest concentration of 1.78%, was found in the KMgS sample. The micro-nutrients with the highest concentration detected in the TSP sample were Cr (45.96 mg/kg), Zn (342.6 mg/kg), and Mn (1331 mg/kg). Non-essential elements such as U, V, La, Sb, Sm, Th, Hf, Sr, Cs, Tb, Sc, Rb, Ta, and Eu were also detected in the fertilizer samples with the highest concentrations in the TSP sample. Statistical tests of multi-nutrient and heavy metals concentrations indicated that multi-nutrient and heavy metals in fertilizers are complex.

Effect of Ascorbic Acid Concentration on the Stability of Tartrate-Capped Silver Nanoparticles Indah Miftakhul Janah; Roto Roto; Dwi Siswanta
Indonesian Journal of Chemistry Vol 22, No 3 (2022)
Publisher : Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/ijc.73196

In this work, tartrate-capped silver nanoparticles (AgNPs) by reducing Ag+ ions into Ag0 using L-ascorbic acid and capping disodium tartrate have been prepared. The reaction was carried out at room temperature in an alkaline medium of pH 11 to obtain a rapid and one-step green synthesis method. The effect of L-ascorbic acid concentration on the synthesis preparation was studied to investigate their impact on the particle size, morphology, and stability of the AgNPs. The obtained tartrate capped AgNPs have SPR absorbance in 390–410 nm. They have a spherical shape, as confirmed by TEM. Increasing L-ascorbic acid concentrations from 25 mM to 100 and 200 mM leads to the 27, 17, and 11 nm particle size distributions. They give the zeta potential of –33.5, –20.8, and –21.3, respectively. After a week, the decreasing absorbance peaks were 0.151, 0.0105, and 0.336 a.u. The optimum L-ascorbic acid concentration was obtained at 100 mM, indicated by the smallest FWHM point. Thus, we may conclude that lower or higher levels of reducing agents resulted in low stability. Therefore, controlling L-ascorbic acid concentration is an important parameter. A sufficient concentration and an appropriate capping agent can produce good nanoparticle stability essential for further application.

Co-Authors Adhitasari Suratman Bella Mellisani Dwi Siswanta Endang Tri Wahyuni Firda Ainun Nissa Hani Prima Rasydta Indah Miftakhul Janah Marcelina Marcelina Mudasir Mudasir Nurul Hidayat Aprilita Sri Juari Santosa Sri Murniasih Taufik Abdillah Natsir

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