Fitria Rahmawati

Ag and Cu loaded on TiO2/graphite as a catalyst for Escherichia coli-contaminated water disinfection

TiO2 film was synthesized by means of the chemical bath deposition (CBD) method from TiCl4 as a precursor and surfactant cetyl trimethyl ammonium bromide (CTAB) as a linking and assembling agent of the titanium hydroxide network on a graphite substrate. Ag and Cu were loaded on the TiO2 film by means of electrodeposition at various applied currents. Photoelectrochemical testing on the composite of Ag-TiO2/G and Cu-TiO2/G was used to define the composite for Escherichia coli-contaminated water disinfection. Disinfection efficiency and the rate of disinfection of E. coli-contaminated water with Ag-TiO2/G as a catalyst was higher than that observed for Cu-TiO2/G in all disinfection methods including photocatalysis (PC), electrocatalysis (EC), and photoelectrocatalysis (PEC). The highest rate constant was achieved by the PEC method using Ag-TiO2/G, k was 6.49 × 10−2 CFU mL−1 min−1. Effective disinfection times of 24 h (EDT24) and 48 h (EDT48) were achieved in all methods except the EC method using Cu-TiO2/G.

Photo- and electro-catalysis for solar disinfection of Escherichia coli-contaminated water using Ag–TiO2/graphite

A titanium dioxide film on a graphite substrate was synthesized by chemical bath deposition from TiCl4 as precursor and with the surfactant cetyl trimethyl ammonium bromide as a linking and assembling agent. Silver was loaded on the TiO2 film by electrodeposition at 0.025 A. Water contaminated with Escherichia coli was disinfected under sunlight irradiation by photolysis (Lys), photocatalysis (PC), photoelectrocatalysis (PEC), and electrocatalysis (EC). The highest rate constant, k, was achieved with EC; k was 5.1 × 10−2 colony forming units (CFU) mL−1 min−1. However, auto-oxidation of Ag occurred during EC and PEC. Meanwhile, the rate constant of disinfection by means of PC was lower than EC and PEC, and k was 3.82 × 10−2 CFU mL−1 min−1. Nevertheless, the auto-oxidation of Ag in the Ag–TiO2/graphite tablet did not occur during the disinfection process.

Optical properties and photocatalytic activity of CdS-TiO2/graphite composite

Abstract TiO2 film was applied to graphite substrate through chemical bath deposition (CBD) method with TiCl4 as precursor. CdS was deposited on TiO2/graphite (TiO2/G) by CBD with precursors of CdSO4. A UV-Vis diffuse reflectance (UV-Vis DR) analysis was used to analyze the optical properties and band gap energy. Meanwhile, photocatalytic activity was determined from the quantum yield (QY) value of isopropanol degradation. The X-ray diffraction pattern shows that the TiO2 film contains rutile and anatase phases. UV-Vis DR spectrum shows the photoactivity in the visible light area and provides lower band gap value due to CdS deposition. TiO2/G provide energy gap at 3.0 eV, which indicates that rutile phase is dominant. Meanwhile, CdS-TiO2/G shows multiple energy gaps representing CdS at 2.4 eV, rutile at 3.0 eV, and anatase at 3.2 eV. The QY values of CdS-TiO2/G are 7.98×10-3 and 8.62×10-4 at 450 and 380 nm of radiation light, respectively. These values are higher than the QY of TiO2/G and TiO2-P25/graphite (TiO2-P25/G), which are 1.19×10-4 and 5.0×10-4, respectively. The photocatalytic reaction follows the first-order reaction. CdS deposition allows the rate constant to increase from 2×10-3 to 13×10-3 under UV radiation.

The performance of LiFePO 4 battery with graphite waste as anode material

A research on the preparation of graphite waste powder from zinc-carbon primary battery has been conducted in order to use the powder as anode material for LiFePO4 (LFP) battery. The result shows that the component of graphite powder is dominated with carbon and some impurities. The LFP battery with graphite waste powder shows charging capacity of ~158 mAh.g-1. The reversibility of Li extraction is 81 % mol. The battery shows discharging capacity of ~ 128 mAh.g-1 at first cycle. It indicates that the performance may decrease fast due to less reversibility of Li extraction.

The Crystal Structure, Conductivity Character and Ionic Migration of Samarium Doped-Ceria (SDC) and its Composite with Sodium Carbonate

This paper discusses the crystal structure, the conductivity character and ionic migration inside Sm0.2Ce0.8O1.9 (SDC) crystal and it’s composite with sodium carbonate salt, Na2CO3 (NSDC). XRD measurement equipped with Le Bail refinement shows that SDC crystallized in single phase of cubic with space group of Fm3m. The addition of Na2CO3 does not change the crystal structure of SDC however it increases the cell parameters. NSDC has a lower ionic conductivity than the SDC at the same temperature. However at 600 °C, SDC provides electronic conductivity which indicates the diffusion of electrons between the electrolyte and electrode caused by the reduction of Ce(IV) to Ce(III). It may cause a short circuit and the fuel cell performance if it is used as electrolyte. Meanwhile, NSDC still produces pure ionic conductivity at 600 °C which indicates a better chemical stability. Based on its capacitance values, it is known that the ionic conductivity of SDC is generated by migration of ions inside grain, while the conductivity of NSDC is generated by the migration of ions between grains or it is named as grain boundaries conductivity.

Preparation of yttria-stabilized zirconia film from an aqueous nano-grain suspension for solid electrolyte

Abstract Yttria-stabilized zirconia film was prepared by casting of a green-nano-grain suspension. The suspension was prepared by considering environmentally friendly of components, that is, water as solvent, α-terpineol as dispersant and glycerin as plasticizer. Addition of surfactant mixture (tween-80 and span-60) was also studied. The prepared film was characterized to understand its diffraction pattern, crystal structure, surface and cross-section morphology, thermal properties and its electrical conductivity in accordance with solid electrolyte application. Analysis found that surfactant addition allows the YSZ film to become wet soon after storing at room condition, instead of to increase quality of product. The film is in the same cubic structure with powder YSZ, as well as the space group. Vibrations at 521.77 cm−1 and 563.24 cm−1 confirm the Zr(Y)-O- vibrations. The average grain size of film is 115.84 ± 6.56 nm, larger than YSZ powder grain size of 81.57 ± 1.08 nm. Impedance measurement confirms only ionic migration to produce conductivity. The value at 800 °C is 3.90 × 10−3 S cm−1 and it could reach 2.35 × 10−2 S cm−1 at 1000 °C. It ensures reliability of the YSZ film for solid electrolyte and also provides a promising way to produce YSZ film from a green aqueous-nano-grain suspension. Graphical Abstract

Application of quantitative XRD on the precipitation of struvite from Brine Water

The present studies have been conducted to quantify the varied phases in struvite formation from brine water as the magnesium source. The quantitative X-ray Diffraction (QXRD) method was performed to quantitatively determine the crystal phases and amorphous content of struvite samples. Substantial phase samples were employed quantitative analysis to calibrate against known phase composition information by Rietveld refinement on powder XRD data. The results showed that brine water could be considered as magnesium source the formation of struvite products. The study demonstrated that in general, the high N:P molar ratio (both pH 9 and 10) might lead to the significant formation of struvite.

The optical properties and photocatalytic activity of CdS-ZnS-TiO2/Graphite for isopropanol degradation under visible light irradiation

This research prepared a photocatalyst tablet of CdS-ZnS-TiO2 on a graphite substrate. The synthesis was conducted through chemical bath deposition method. The graphite substrate used was a waste graphite rod from primary batteries. The aims of this research are studying the crystal structure, the optical properties and the photocatalytic activity of the prepared material. The photocatalytic activity was determined through isopropanol degradation. The result shows that the TiO2/Graphite provide direct transition gap energy at 2.91 eV and an indirect transition gap energy at 3.21 eV. Deposition of CdS-ZnS changed the direct transition gap energy to 3.01 eV and the indirect transition gap energy to 3.22 eV. Isopropanol degradation with the prepared catalyst produced new peaks at 223-224 nm and 265-266 nm confirming the production of acetone. The degradation follows first order with rate constant of 2.4 × 10−2 min−1.

Structure and morphological analysis of various composition of yttrium doped-zirconia prepared from local zircon sand

Yttrium ions, Y3+ were doped into ZrO2 that was synthesized from zircon sand. Zircon sand is a side product of tin mining plant in Bangka Island, Indonesia. Solid state reaction was chosen as the method to dope yttrium ions from Y2O3 into ZrO2 at various % mol of 4.5; 8 and 10. This research aims to understand the crystal structure, morphological analysis and particle size analysis. The X-ray diffraction analysis equipped with Le Bail refinement found that the prepared ZrO2 is in two phases of the monoclinic and tetragonal structure, and the structure changed to cubic after yttrium ions doping. However, the monoclinic and tetragonal still exist. Various yttrium concentrations provide different morphology, in which 4.5 YSZ shows a blocking phase indicated as the presence of impurities. The blocking phase seems to prevent sintering and allows a line crack on the material layer. Meanwhile, 8YSZ and 10YSZ show homogeneous morphology and without provides a line crack. The mean particle size after sintering is in between 1.1 - 1.5 μm.

Electrical conductivity of zirconia and yttrium-doped zirconia from Indonesian local zircon as prospective material for fuel cells

In this research, zirconium dioxide, ZrO2, was synthesized from high-grade zircon sand that was founded from Bangka Island, Sumatra, Indonesia. The zircon sand is a side product of Tin mining plant industry. The synthesis was conducted by caustic fusion method with considering definite stoichiometric mole at every reaction step. Yttrium has been doped into the prepared zirconia by solid state reaction. The prepared materials were then being analyzed by X-ray diffraction equipped with Le Bail refinement to study its crystal structure and cell parameters. Electrical conductivity was studied through impedance measurement at a frequency range of 20 Hz- 5 MHz. Morphological analysis was conducted through Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-ray (EDX) for elemental analysis. The results show that the prepared yttrium stabilized zirconia, YSZ, was crystallized in the cubic structure with a space group of P42/NMC. The sintered zirconia and yttrium stabilized zirconia at 8 mol% of yttrium ions (8YSZ) show dense surface morphology with a grain size less than 10 pm. Elemental analysis on the sintered zirconia and 8YSZ show that sintering at 1500°C could eliminate the impurities, and the purity became 81.30%. Impedance analysis shows that ZrO2 provide grain and grain boundary conductivity meanwhile 8YSZ only provide grain mechanism. The yttrium doping enhanced the conductivity up to 1.5 orders. The ionic conductivity of the prepared 8YSZ is categorized as a good material with conductivity reach 7.01 x10-3 at 700 °C. The ionic conductivities are still lower than commercial 8YSZ at various temperature. It indicates that purity of raw material might significantly contribute to the electrical conductivity.