Electrochemical Disinfection of Simulated Ballast Water Using RuO2-TiO2/Ti Electrode

The present work investigated the treatment of ballast water via electrochemical disinfection using a RuO2-TiO2/Ti electrode. Batch tests were conducted with simulated ballast water containing Escherichia coli as an indicator organism. The effect of varying NaCl concentrations (1%, 2%, and 3%; w/v) and current densities (0.3, 1.0, 2.0, and 3.0 mA/cm2) on the inactivation of E. coli was examined. Results showed higher disinfection efficiency of E. coli was obtained at higher NaCl concentration and current density. Complete inactivation of E. coli was attained within 2 and 1 min at 0.3 and 1 mA/cm2, respectively, under 3% NaCl concentration. Meanwhile, complete disinfection at 1 and 2% NaCl concentrations was observed in 6 and 2 min, respectively, using a current density of 0.3 mA/cm2. The 100% inactivation of E. coli was achieved with an energy consumption in the range of 2.8 to 2.9 Wh/m3 under the NaCl concentrations at 1 mA/cm2 and 1 min of electrolysis time. The complete disinfection attained within 1 min meets the D-2 standard (<250 CFU E. coli/100 mL) of ballast water under the International Maritime Organization. The values of energy consumption of the present work are lower than previous reports on the inactivation of E. coli from simulated ballast water

Oil Adsorption Kinetics of Calcium Stearate-Coated Kapok Fibers

This study used a simple and efficient dipping method to prepare oleophilic calcium stearate-coated kapok fibers (CaSt2-KF) with improved hydrophobicity. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) confirmed the deposition of calcium stearate particles on the surface of the kapok fibers. This led to higher surface roughness and improved static water contact angle of 137.4°. The calcium stearate-coated kapok fibers exhibited comparable sorption capacities for kerosene, diesel, and palm oil. However, the highest sorption capacity of 59.69 g/g was observed for motor oil at static conditions. For motor oil in water, the coated fibers exhibited fast initial sorption and a 65% removal efficiency after 30 s. At equilibrium, CaSt2-KF attained a sorption capacity of 33.9 g/g and 92.5% removal efficiency for motor oil in water. The sorption kinetics of pure motor oil and motor oil in water follows the pseudo-second-order kinetic model, and the Elovich model further described chemisorption. Intraparticle diffusion and liquid film diffusion were both present, with the latter being the predominant diffusion mechanism during motor oil sorption

Adsorption of Lead from Aqueous Solution Using Activated Carbon Derived from Rice Husk Modified with Lemon Juice

In the present work, activated carbon (RHAC-LJ) was synthesized utilizing rice husk as a carbon source that is activated with lemon juice. Moreover, the adsorptive capacity of RHAC-LJ in removing Pb(II) from aqueous solution was investigated. FTIR analysis revealed the presence of amides, alkenes, carboxyl and hydroxyl groups in RHAC-LJ. SEM micrographs illustrate that activation with lemon juice resulted in high pore volume and greater pore diameter. Activation using acid from lemon juice can remove impurities from the adsorbent surface. The surface area and pore volume of RHAC-LJ were determined to be 112.87 m2·g−1 and 0.107 cm3/g, respectively. Adsorption kinetics followed the pseudo-second-order equation (R2 = 0.9941) with a rate constant of 3.3697 g/mg·min for Pb (II), which indicates chemisorption to be the rate-determining step of the process. The BBD model using RSM was applied in studying the effects of pH, stirring speed and adsorbent dosage and their interactions on the removal efficiency of RHAC-LJ. Analysis of variance was used to examine the significance of the model, independent parameters, and their interactions. Moreover, a removal efficiency of 98.49% can be attained using the following optimal conditions: 197 rpm, pH 5.49, and adsorbent dosage of 0.3487 g. Overall, the present work illustrates RHAC-LJ as a potential low-cost adsorbent for the removal of Pb(II) from synthetic wastewater