Photocatalytic treatment of real liquid effluent from hydrothermal carbonization of agricultural waste using metal doped TiO2/UV system.

This study investigated treatment of real liquid effluent generated from hydrothermal carbonization (HTC) of macadamia nut shell by employing transition metals Cu, Ni, and Fe doped titanium dioxide (TiO2) photocatalysts. The anatase TiO2 based photocatalysts were prepared via sol-gel method, and calcined at 400 °C. The modification with metal dopants was performed via ultrasonic assisted incipient wetness impregnation method. The prepared photocatalysts were characterized using XRD, UV-Vis DRS, SEM-EDX, and N2 physisorption. The influence of metal dopants, types of TiO2 support, and initial pH of the wastewater on the photocatalytic degradation performance of total organic carbon (TOC) and chemical oxygen demand (COD) in the wastewater were investigated. The results revealed that Fe doped TiO2 exhibited the highest photocatalytic activity followed by Cu and Ni, respectively. Among all, Fe doped anatase TiO2 were the most promising catalyst as it performed the highest removal of 75.1% for TOC and 94.1% for COD after 1 h irradiation at pH 4, achieving the lowest TOC and COD concentration of 405.62 mg/L and 91.26 mg/L, respectively. The findings suggested that photocatalytic degradation of HTC liquid effluent could be a potential treatment before releasing the wastewater to the environment.

Lignin removal from synthetic wastewater via Fenton-like reaction over Cu supported on MCM-41 derived from bagasse: Optimization and reaction intermediates.

Lignin degradation was performed using a Fenton-like oxidation reaction with Cu supported on MCM-41, derived from bagasse (Cu-BG-MCM-41), as the catalyst. The optimal degradation conditions required to remove a predetermined amount of lignin (95%) from an effluent were determined. Based on the literature review and preliminary tests, the critical parameters determining the operating conditions include temperature, catalyst loading, pH, H2O2 concentration, and reaction time. The experimental design and working conditions were based on Box-Behnken design. The reaction products were analyzed via UV-vis and gas chromatography-mass spectrometry. Response surface methodology (RSM) was used to predict the optimum operating conditions for the Fenton-like reaction for 95% lignin degradation, which were a temperature of 80 °C, initial pH of 9, H2O2 concentration of 1 mL/L, catalyst loading of 1.0 g/L, and reaction time of 30 min. These conditions were validated three times and the achieved percentage of lignin degradation was 95 ± 2%. This is close to the value of 95% used in the RSM to determine the optimum operating conditions, thus verifying the model. The catalyst was stable and functioned well under the optimum design conditions. Moreover, the reaction could be used to obtain high-value intermediate products if stopped after 5 min. Finally, lignin was degraded into vanillin, a higher-value product. As expected, the proposed Fenton-like approach expanded the pH working range from less than 4 to 5-9.

Degradation of formaldehyde by photo-Fenton process over n-ZVI/TiO2 catalyst.

The degradation of formaldehyde in a photo-Fenton reaction was studied using n-ZVI/TiO2 as the catalyst. The effects of %n-ZVI loading, catalyst dosage, H2O2, and pH on formaldehyde degradation were studied. The n-ZVI/TiO2 catalysts were prepared by impregnation with chemical reduction, and their catalytic activity was evaluated in a batch reactor under UVC light. Transmission electron microscopy (TEM) was used to determine that the n-ZVI nanoparticle size was 39.41 nm. X-ray photoelectron spectroscopy (XPS) was used to study the oxidation states of 2%n­ZVI/TiO2, and the Fe 2p spectrum of 2%n-ZVI/TiO2 indicated the presence of Fe0. The optimal conditions for the complete removal of formaldehyde within 30 min were an n-ZVI loading of 2 wt.%, a catalyst dosage of 0.5 g/L, 30 mM H2O2, and an initial pH of 3. After the reaction, the C-H functional group of formaldehyde was not observed due to the •OH radicals generated by Fe0 and H2O2 attacking the formaldehyde molecule. Moreover, no Fe leaching was observed, presenting an advantage compared with homogeneous Fe catalysts. Therefore, 2%n­ZVI/TiO2 shows excellent potential as a photo-Fenton catalyst for the environmentally friendly degradation of formaldehyde.

Comparison of dehydration methods for untreated lignin resole by hot air oven and vacuum rotary evaporator to synthesize lignin-based phenolic foam.

We investigate two different dehydration methods to determine their suitability for preparing resoles for foam synthesis. A simplified process for synthesizing lignin foam (LF) from lignin resole (LR) dehydrated in a hot air oven (HAO) is compared with that dehydrated using a vacuum rotary evaporator (VRE). First, the LR formulation is prepared by mixing phenol with untreated lignin (0%-15% by weight), and subsequently, the prepared LRs are dehydrated using an HAO and a VRE. We find that for the same dehydration time, both techniques yield LRs with the same chemical compositions; however, the HAO technique affords a moisture removal of 13-17% by weight, whereas the VRE technique removes 9-12% moisture by weight. The LR obtained by the HAO is more viscous and maintains a circular shape after being dropped on a plate. In our experimental synthesis of LF containing VRE resole, biofoam is not formed owing to insufficient viscosity, whereas biofoam is obtained with the HAO resole. The synthesized LF exhibits a density range of 44.96-85.68 kg/m3 and a compressive strength of 103.28-152.27 kPa. Scanning electron microscopy investigations show that the morphology of the foam is a closed-cell structure. The simplified synthesis of LF from the HAO-treated resole offers significant advantages over the complexity of the conventional VRE approach in terms of equipment cost and energy consumption. The resulting foam exhibits a thermal stability and thermal performance comparable with the counterpart properties of phenolic foam.

Morphology study of zinc anode prepared by electroplating method for rechargeable Zn-MnO2 battery.

Zinc electrodes prepared by electrodepositing zinc on a copper plate in ZnSO4 electrolyte were studied to determine the most suitable condition of zinc anode preparation for high performance Zn-MnO2 battery. Deposition of zinc on substrate material was confirmed using X-ray diffraction (XRD) measurement. Morphological characterization of zinc anode was performed by scanning electron microscopy (SEM). It was observed that concentration of electrolyte and electrical current density influenced the morphology of zinc electrode. At 1 M ZnSO4 and current density values of 0.06-0.1 A/cm2, it was found that the morphological structure of zinc electrode was orderly arranged in a layer-by-layer structure. This indicated that the current density played an important role on deposition morphology and even on the crystal structure. Performance of electrodes was tested by a battery analyzer for 100 cycles. The results of the tests showed that the electrode with the layer-by-layer morphology yielded a high efficiency of up to 99.97% which was higher and more stable than those of the electrodes with disordered and scattered morphology. The layer-by-layer morphology is therefore a key factor for improving the performance of Zn-MnO2 cell.

Optimizing chemical oxygen demand removal from synthesized wastewater containing lignin by catalytic wet-air oxidation over CuO/Al2O3 catalysts.

UNLABELLED: In this study, 10% CuO/Al2O3 catalyst was used in a catalytic wet-air oxidation process to remove chemical oxygen demand (COD) and color from experimentally designed wastewater containing lignin. The catalyst was prepared using an impregnation method and was characterized by X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), and Brunauer-Emmett-Teller method (BET) for surface area before use. A series of Box-Behnken design (BBD) experiments were used to identify the conditions (temperature, pressure, reaction time, and catalysts) necessary for the COD removal process. The predicted model had R2 and R2adj correlation coefficients of 0.98 and 0.97, respectively. Pressure only and the interaction effect between temperature and pressure were found to have a significant effect on COD removal (both confidence interval [CI] 95%). Finally, response surface methodology (RSM)-optimized results suggested that 92% of COD could be removed in 1 L of experimental wastewater with a lignin concentration 350 g/L in 120 min under the following conditions: a reaction temperature of 185 °C, a pressure of 10 bars, and catalyst loading of 1 mg/L. The experiment, performed in triplicate, yielded a COD removal of 90±2%. The results are believed to be of importance to pulp and paper industrial wastewater treatment and other similar applications. IMPLICATIONS: Catalytic wet-air oxidation (CWAO) has been used as an alternative to overcome problems related to the high temperatures and pressures required by the traditional wet-air oxidation. CWAO has been widely applied to treat various industrial wastewaters. To reduce the overall operational cost, it is necessary to identify the optimal condition required when designing wastewater treatment plant processes. In this work, the authors had successfully demonstrated the application of response surface methodology (RSM) with the Box-Behnken design (BBD) as a means of elucidating the complicated interaction effects between parameters.

Characterization of platinum-iron catalysts supported on MCM-41 synthesized with rice husk silica and their performance for phenol hydroxylation.

Mesoporous material RH-MCM-41 was synthesized with rice husk silica by a hydrothermal method. It was used as a support for bimetallic platinum-iron catalysts Pt-Fe/RH-MCM-41 for phenol hydroxylation. The catalysts were prepared by co-impregnation with Pt and Fe at amounts of 0.5 and 5.0 wt.%, respectively. The RH-MCM-41 structure in the catalysts was studied with x-ray diffraction, and their surface areas were determined by nitrogen adsorption. The oxidation number of Fe supported on RH-MCM-41 was + 3, as determined by x-ray absorption near edge structure (XANES) analysis. Transmission electron microscopy (TEM) images of all the catalysts displayed well-ordered structures, and metal nanoparticles were observed in some catalysts. All the catalysts were active for phenol hydroxylation using H2O2 as the oxidant at phenol : H2O2 mole ratios of 2 : 1, 2 : 2, 2 : 3 and 2 : 4. The first three ratios produced only catechol and hydroquinone, whereas the 2 : 4 ratio also produced benzoquinone. The 2 : 3 ratio gave the highest phenol conversion of 47% at 70 °C. The catalyst prepared by co-impregnation with Pt and Fe was more active than that prepared using a physical mixture of Pt/RH-MCM-41 and Fe/RH-MCM-41.