Key Engineering Materials Vol. 920

Abstract: Copper (Cu) was deposited on two different types of zinc oxide (ZnO), namely commercial ZnO (CZ) and mesoporous zinc oxide (MZ), using a simple electrolysis technique. The catalysts were characterized by XRD, FTIR, BET and UV-Vis DRS. The synergistic effect between Cu, CZ and MZ was tested in the degradation of 2,4-dichlorophenol (2,4-DCP) under visible light irradiation. Cu-MZ exhibited the best performance with 97% degradation compared to MZ, Cu-CZ, CZ and CuO with 80%, 70%, 55% and 49%, respectively. The introduction of Cu in CZ and MZ was found to decrease the band gap energy of ZnO from 3.20 to 3.05 eV and 2.90 to 2.60 eV, respectively. The role of Cu in reducing the band gap energy of Cu-CZ and Cu-MZ probably contributed significantly to the good photocatalytic degradation of 2,4-DCP.

Abstract: Ammonia is a harmful substance on wastewater if discharged to the river, then it must be treated well. This research was aimed to examine the potential for the type of bacteria Brevundimonas diminuta in the ammonia degradation process of wastewater. Earlier step was done to examine bacteria growth in synthetical medium of ammonia concentration ranged 5 – 25 ppm. It shows that the bacteria could grow well within that ranges. Then, the bacteria performances were examined to grow in wastewater sampled from Musi River containing ammonia ranged 1.9 – 2.94 mg/L in the airlift bioreactor. The wastewater used in bioreactor was 1 L. Air was injected into the bioreactor with variations in the air flow rate of 1.5 to 4.5 L/m and with varying observation times from 1.5 to 6 hours. The optimal decrease in ammonia levels has occurred when the air flow rate was 3 L/min for 6 hours and the ammonia level was reduced from 2.94 mg/L to 1.76 mg/L.

Abstract: The development of Ag₃PO₄ photocatalyst for dye waste treatment is necessary because of its superiority compared to other materials. In this research, Ag₃PO₄ was synthesized with AgNO₃ and HAp from milkfish bones. Syntesis was done by simple ion-exchange method. In this research, composition of AgNO₃:HAp are 1:0.1; 1:0.3; and 1:0.5 to determine the optimum composition. Based on XRD results, it shows that ion-exchange process between phosphate ions from HAp milkfish bones and Ag+ from AgNO₃ was imperfect. It was shown from the presence of HAp peaks in synthesis results. Furthermore, the diffraction pattern showed that AgNO₃:HAp 1:0.1 composition has the best cristalinity. Based on SEM characterization, it shows that all compositions have majority shape as spherical and small part at AgNO₃/HAp 1:0.5 composition has nanorod morphology. It was also known that material with composition of AgNO₃:HAp 1:0.1; 1:0.3 and 1:0.5 have average size are 100.76 nm, 92.31 nm and 107.51. From UV-Vis spectroscopy data processing, it represent the value of direct band gap of material is 3.83 eV and the value of indirect band gap is 3.6 eV. It also shows the degradation value of methylene blue with the best value was shown in AgNO₃:HAp 1:0.3 composition with 47.4%.

Abstract: Two hydroxy-functionalized PAMAM Dendrimers (3OH-PAMAM and 4OH-PAMAM) were developed as immobilized liquid membranes (ILMs) to separate CO₂ from a mixture of CO₂ and N₂. The hydroxy-functionalized PAMAM demonstrated excellent properties of CO₂-selective separative material for CO₂ membrane separation. The hydroxy-functionalized PAMAM dendrimers displayed greater water sorption and more CO₂ separation properties than that of conventional PAMAM without hydroxy groups. The resulting ILMs of 4OH-PAMAM showed the highest CO₂ over N₂ selectivity of 7000 and above with CO₂ permeance of 1.1×10⁻¹¹ m³ (STP) m⁻² s⁻¹ Pa⁻¹ (1.5 GPU, 1 GPU = 7.5 × 10⁻¹² m³ (STP) m⁻² s⁻¹ Pa⁻¹), with a membrane thickness of 100µm (CO₂ permeability 147 Barrers), at 9.7 kPa CO₂ partial under 130 kPa feed pressure with 80% RH at 40 °C. For the ILMs of dendrimers at over 60%RH, their P_CO2 – α plots exceeded the upper bound line by Roberson in 2008 and that is a potential for CO₂ separation from the gas mixture.

Abstract: Wastewater from the LFP battery cathode recycling process still contains metals such as lithium, calcium, sodium, and silica. Adsorption method was used to remove metal ions in the artificial waste of LFP batteries. This experiment was carried out by adding 2, 4, 6, 8, and 10 g of activated carbon, respectively, into 100 mL of an artificial waste solution then put into water-bath shaker at room temperature. For kinetic data, the filtrate was taken every 1 hour, while for equilibrium data the filtrate was taken every 24 hours. The concentrations of the initial solution and the filtrate were analyzed by ICP-OES. The experimental results showed the maximum percentage removal of lithium, calcium, sodium, and silica was at a dose of 100 g L^-1 of activated carbon, which were 99.90%, 97.51%, 86.10%, and 79.08%, respectively. It was found that the Freundlich equilibrium model was more suitable for the adsorption isotherm indicated by the correlation coefficients value for lithium, calcium, sodium, and silicon were 0.9869, 0.8850, 0.8974, and 0.9576, respectively. This adsorption followed the Pseudo second order kinetic model derived from correlation coefficient values of chemical kinetic studies.

Abstract: The synthesis of zinc oxide and nano-composite ZnO/TiO₂ was successfully prepared using lignin extracted from an oil palm empty fruit bunch. The synthesized materials i.e. zinc oxide and nano-composite ZnO/TiO₂ were characterized by UV–Vis spectrophotometry (UV-Vis), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystalline nature of ZnO and ZnO/TiO₂ nanocomposite is indicated by XRD analysis and SEM images. The result of UV–vis spectrophotometry shows the red shift occurred in the case of ZnO/TiO₂ composite. The nano range of the particles was demonstrated by the TEM images. The photocatalytic activity of the synthesized nanocomposite ZnO/TiO₂ was tested and compared to ZnO for the decolorization of rhodamine B. The decolorization results indicate that ZnO/TiO₂ nanocomposite showed better photocatalytic activity under visible light than ZnO as well as TiO₂.

Abstract: Sulfuric acid cross-linked chitosan/pectin polyelectrolyte complex (CPS) film was prepared as sodium dodecyl sulfate (SDS) adsorbent. CPS films were prepared in various compositions of chitosan/pectin and cross-linked by immersion in 0.1 M H₂SO₄ solution. CPS films were characterized using FTIR and SEM. CPS film was used for SDS adsorption with parameters of film composition, contact time, pH, initial SDS concentration. FTIR spectra showed characteristic peaks for chitosan, pectin and their interaction with sulfuric acid. The surface of the CPS film changed to become smoother after being used for SDS adsorption. CPS film composition 70:30 showed the highest percent swelling and was stable at the overall pH. The optimum conditions for SDS adsorption by sulfuric acid cross-linked chitosan/pectin CPS film occurred at a contact time of 120 minutes, pH 5, initial concentration of SDS 100 mg L^–1 with a film composition of 70:30. Adsorption followed the pseudo-second-order kinetic and Freundlich isotherm models with K_F and n of 0.0297 and 0.377, respectively. The highest SDS desorption of 97.6% was achieved using 0.1 M NaClO₄ solution.

Abstract: Biofilm enhances the performances of biological wastewater treatment systems. This study aimed to investigate the feasibility of using biodegradable polyhydroxyalkanoate (PHA) pellets as novel biofilm carrier for phenol biodegradation. Two identical laboratory-scale reactors were operated with fill, react, settle, draw and idle periods in the ratio of 2:12:2:1:7 for a 24-h cycle. One reactor was supplemented with 2% (v/v) of PHA pellet and operated as sequencing batch biofilm reactor (SBBR), whereas the other reactor was operated as sequencing batch reactor (SBR) and used as the control reactor. The performances of SBBR and SBR in degrading phenol were studied at three phases with the introduction of 300, 500 and 1000 mg L^-1 phenol, respectively. The removal of phenol was found best described using zero-order kinetics, with R² > 0.97. At all phases, the phenol removal rate during react period for SBBR (7.30 ± 0.55 to 9.33 ± 1.06 mg L^-1 min^-1) was found higher compared to those for SBR (4.28 ± 0.66 to 8.35 ± 0.68 mg L^-1 min^-1), with significance difference observed at low phenol concentration. Whereas for chemical oxygen demand biodegradation kinetics, SBRR exhibited significantly higher rate compared to SBR at all phases. From the scanning electron microscopy image, the attachment of activated sludge onto PHA pellet was observed. The results indicated the potential of PHA serving as alternative biofilm carrier in biofilm process.

Abstract: Fenton process involving Fe²⁺ ions and H₂O₂ produces OH radicals, that act as a strong oxidizing agent for degradation of a variety of organic pollutants. However the process is poor performance at neutral pH limiting its application for industrial wastewater treatment. The short coming problem, in the current study, is solved by introducing ethylene diamine tetra acetic acid (EDTA) as a complexing compound. The degradation was conducted through batch experiment, by varying EDTA concentration and pH. In addition, the Fe²⁺ and H₂O₂ concentrations, and the reaction time were optimized. The research results assign that the addition of EDTA could remarkably enhance the degradation of anionic surfactant, that was 96% at pH 6-8. The increase of the degradation was proportional to the concentrations of EDTA and 6 mg/L showed the optimum level. The highest degradation of 162 mg/L anionic surfactant in 20 mL of the laundry wastewater could be achieved within 30 mins by using Fe²⁺ 10 mM, H₂O₂ 50 mM, and in the pre12sence of EDTA 6 mg/L at pH 7. Key words : Fenton, EDTA, degradation, surfactant, wastewater