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The massive drawbacks of conventional wastewater treatment have led to a demand investigation about new advanced wastewater treatment technology. The issue can be addressed via advanced oxidation p...

Photocatalytic fuel cell (PFC) is promising to own its synchronous degradation of organic pollutants with electricity generation under illumination of light. The oxidation and reduction process promote the conversion of chemical energy in the pollutants into electrical energy. In this study, PFC is driven by the electrode reactions between the zinc oxide loaded carbon plate (ZnO/C) photoanode and carbon plate cathode under irradiation of UVA light. The ZnO/C photoanode was successfully fabricated by using simple ultrasonication-annealed method and investigated by XRD, SEM and EDX. To investigate the capability of the PFC, reactive red 120 (RR120), congo red (CR) and acid orange 7 (AO7) are employed well compared among themselves. The results indicated that the molecular structure of azo dyes with different adsorption of light by dye itself, number of azo bonds and sulfonic groups can be the crucial factors of decolorization in the PFC. The photocatalytic fuel cell with AO7 as sacrificial agent was able to perform 82.43% of decolorization efficiency, a maximum short circuit current (JSC) of 0.0017 mA cm-2 and maximum power density (Pmax) of 0.0886 µW cm-2.

Photocatalytic fuel cell (PFC) is considered as a sustainable green technology which could degrade organic pollutant and generate electricity simultaneously. A synergistic double-sided ZnO/BaTiO3 loaded carbon plate heterojunction photoanode was fabricated in different ratios by using simple ultrasonication and mixed-annealed method. The double-sided design of photoanode allowed the lights irradiated at both sides of the photoanode. The ferroelectricity fabricated photoanode was applied in a membraneless PFC with platinum-loaded carbon as the cathode. Results revealed that the photoanode with 1:1 ratio of BaTiO3 and ZnO exhibited a superior photocatalytic activity among all the photoanodes prepared in this study. The heterojunction of this photoanode was able to achieve up to a removal efficiency of 93.67% with a maximum power density of 0.5284 μW cm−2 in 10 mg L−1 of Reactive Red 120 (RR120) without any supporting electrolyte. This photoanode was able to maintain at high performance after recycling 3 times. Overloading of ZnO above 50% on BaTiO3 could lead to deterioration of the performance of PFC due to the charge defects and light trapping ability. The interactions, interesting polarizations of the photocatalysts and proposed mechanism of the n-n type heterojunction in the photoanode of ZnO/BaTiO3 was also discussed.

The concentrations of supporting electrolyte and external resistance (Rext) played crucial roles to improve photocatalytic fuel cell (PFC) efficiency. Herein, the significant influence of Na2SO4 concentration (0.05–0.20 M) and the Rext (100, 280, 500, 1000 and 10,000 Ω) on the power production and dye decolorization in PFC were addressed. Analysis of variance (ANOVA) revealed that the further increment of 0.10 M of Na2SO4 concentration only enhanced maximum power density (Pmax) but had no significant effect on the dye decolorization (P > 0.05). Conversely, the result showed distinct differences in PFC performances under different Rext (P

A novel sustainable hybrid system of photocatalytic fuel cell (PFC) and Fenton process is an alternative wastewater treatment technology for energy-saving and efficient treatment of organic pollutants. The electrons generated from PFC photoanode are used to produce H2O2 in the Fenton reactor and react with the in situ generation of Fe2+ from sacrificial iron for hydroxyl radical formation. In this study, the effect of different initial Amaranth dye concentrations on degradation and electricity generation were investigated. ZnO/Zn photoanode was prepared by anodizing method and characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Results revealed that the maximum power density (9.53 mW/m2) and current density (0.0178 mA/m2) were achieved at 10 mg/L of Amaranth. The correlation between dye degradation, voltage output, and kinetic photocatalytic degradation were also investigated and discussed.

A novel hybrid system composed of a photocatalytic fuel cell (PFC) and Fenton reactor was developed with the aim to degrade the azo dye Reactive Black 5 (RB5) and generate electricity. Compared to previously established system of bioelectro-Fenton system, microbial fuel cell (MFC) system has significant challenge in the development and operation system. Therefore, PFC is used instead of MFC to generate electrons for the Fenton system. The effect of azo dye (RB5) on each PFC and Fenton reactor was investigated. The experimental results showed that maximum power output was achieved in the absence of dye in the Fenton reactor of this hybrid system. Furthermore, higher degradation efficiency of RB5 could also be observed in the PFC reactor in this hybrid system.

Reactive Green (RG19) is one of azo dye that potentially hazardous towards human due to highly recalcitrant to degrade and still lack of effective treatments. This study introduced a significant study since numerous conventional treatment processes were not capable of removing that azo dye in fast and efficient process. Therefore, increase strong potential of sulfate and hydroxyl radical resulting in an improvement towards Advanced Oxidation Processes (AOPs) which is ozonation process has been proposed to degrade RG19 dye efficiently. Ozonation (O3) and Ozone/Persulfate (O3/S2O82-) processes were tested either can be a standalone process or need a better combination of a catalyst which is sodium persulfate (Na2S2O8). The efficiency of dye degradation as follows: colour removal, chemical oxygen demand (COD) and the presence of organic molecules. The efficiency colour removal with O3 reached 75% while (O3/S2O82-) reached 85% at similar reaction time. Also, the average rate of efficiency COD removal (O3/S2O82-) yielded the highest 27.82% whereas O3 reached only 10%. After that, the effects of operational conditions had been investigated in (O3/S2O82-) process including the fixed initial concentration of the dyes, initial pH of the RG19 (2-6), Na2S2O8 concentration (25-65 mM) and contact time (3-25 min) on the colour and COD removal efficiency. Central composite design (CCD) has been applied to achieve the optimization of (O3/S2O82-) was resulting (Colour removal; R2 = 0.900, COD removal; R2 = 0.508). Hence, the optimum conditions of the process at (pH 8, 40 mM, 14 min) and can be shown specifically by mathematical modelling equation also based on interactive effect by 3D contour plot. This overall result indicates that (O3/S2O82-) process enhances a synergistic effect that could be observed in structural changes of dye molecule along RG19 degradation.Reactive Green (RG19) is one of azo dye that potentially hazardous towards human due to highly recalcitrant to degrade and still lack of effective treatments. This study introduced a significant study since numerous conventional treatment processes were not capable of removing that azo dye in fast and efficient process. Therefore, increase strong potential of sulfate and hydroxyl radical resulting in an improvement towards Advanced Oxidation Processes (AOPs) which is ozonation process has been proposed to degrade RG19 dye efficiently. Ozonation (O3) and Ozone/Persulfate (O3/S2O82-) processes were tested either can be a standalone process or need a better combination of a catalyst which is sodium persulfate (Na2S2O8). The efficiency of dye degradation as follows: colour removal, chemical oxygen demand (COD) and the presence of organic molecules. The efficiency colour removal with O3 reached 75% while (O3/S2O82-) reached 85% at similar reaction time. Also, the average rate of efficiency COD removal (O3/S2O8...

A unidirectional flow solar photocatalytic fuel cell (PFC) was successfully developed for the first time to offer alternative for electricity generation and simultaneous wastewater treatment. This study was focused on the synthesis of α-, δ- and β-MnO2 by wet chemical hydrothermal method for application as the cathodic catalyst in PFC. The crystallographic evolution was performed by varying the ratios of KMnO4 to MnSO4. The mechanism of the PFC with the MnO2/C as cathode was also discussed. Results showed that the catalytic activity of MnO2/C cathode was mainly predominated by their crystallographic structures which included Mn–O bond strength and tunnel size, following order of α- > δ- > β-MnO2/C. Interestingly, it was discovered that the specific surface areas (SBET) of different crystal phases did not give an impact on the PFC performance. However, the Pmax could be significantly influenced by the micropore surface area (Smicro) in the comparison among α-MnO2. Furthermore, the morphological transformation carried out by altering the hydrothermal duration demonstrated that the nanowire α-M3(24 h)/C with 1:1 ratio of KMnO4 and MnSO4 yielded excellent PFC performance with a Pmax of 2.8680 μW cm−2 and the lowest Rint of 700 Ω.

In this paper, a respond surface methodology (RSM) model has been developed using three levels Box-Benkhen experimental design (BBD) technique to study the influence of several metal-assisted chemical etching (MACE) process variables on the properties of nanostructured silicon (Si) wafer. Five process variables are examined i.e. concentrations of silver (Ag), hydrofluoric acid (HF), deposition time, H2O2 concentration and etching time as a function of etching rate. Design-Expert® software (version 7.1) is used in formulating the RSM model of five factors with 46 experiments. A regression quadratic model is developed to correlate the process variables where the most significant factors are identified and validated using analysis of variance (ANOVA). The model for etching rate is found to be significant with R2 of 0.8, where both Ag concentrations and etching time are the major influence.

Developing an effective interface interaction between photoanode and electrolyte is crucial for achieving superior photocatalytic fuel cell (PFC) performance. In this aspect, the contribution of the medium or electrolyte properties in the PFC system such as dye concentration, ionic nature and active radicals play a decisive role. Herein, we constructed a PFC with ZnO loaded nickel foam (ZnO/Ni) photoanode to study the influence of initial dye concentration, pH and supporting electrolytes of different polyatomic anions on the PFC performance. The optimum initial dye concentration and pH for the PFC with reactive red 120 as organic pollutants were found to be 30 mg L−1 and 7.5, respectively. The PFC performance can be synergistically enhanced by the addition of three types of polyatomic anions (Na3PO4, Na2SO4 and NaNO3) as supporting electrolytes. In turn, PO43- had the greatest influence on the reduction of internal resistance (highest short circuit current, Jsc) which corresponded to the conductivity of dye solution. Eventually, the higher charge of polyatomic ions could contribute to higher energy conversion efficiency in PFC. Nonetheless, SO42- anions favoured the cleavage of aromatic compounds by the advantage of recycling between SO42- and SO4 - through hole scavenging activity. Comprehensively, our findings provided new insight into the selection of supporting electrolyte as well as the proposed mechanism of active radicals involved in PFC. Additionally, the ZnO/Ni photoanode demonstrated its excellent recyclability as it retained high PFC performance after five consecutive runs.

Dyes often being use in many manufacturing processes. Hence, the wastewater resulted from the manufacturing process contain colour which need to be removed before being emitted into any water bodies. Photocatalysis is a method which effectively treating wastewater using photocatalyst. ZnO is an example of semiconductor material which is use as a photocatalyst in the treatment method. Doping with transition metals can improve its properties to maximize its photocatalytic efficiency. In this study, the effect of zinc oxide (ZnO) and zinc oxide doped Fe (ZnO/Fe) photocatalyst for dye removal efficiency were investigated. The photocatalysts were successfully synthesized through sol-gel method and characterized by SEM, FTIR and EDX. The photocatalytic efficiency of ZnO and ZnO/Fe was studied by degrading methylene blue (MB) under the exposure of 3 hours of sunlight with varies operational condition. Optimal photocatalytic efficiency operating parameters were performed by Design Expert 10 using the Response Surface Method (RSM). ZnO appeared as regular shape compared to ZnO/Fe which most of the particles had clumped together. The removal efficiency of MB was increase when the dosage of catalyst increased. However, once the optimum dosage of catalyst exceeded, the removal efficiency of MB reduced. During the experiment, 30 mg of ZnO was capable to remove 90% of MB from the solution. When while, ZnO/Fe exhibited better result as it could remove up to 95% of MB using only 10 mg of ZnO/Fe during the treatment. It can be concluded that doping the ZnO with Fe could improve the catalytic ability of ZnO to degrade MB in wastewater.

Nano zero-valent iron (nZVI) has received great attention for its capability to treat wastewater. One of its applications is in an advanced oxidation process (AOP) called the sono-Fenton process. This study presents the characterization of the nZVI particle by its particle size, scanning electron microscope (SEM) images, transmission electron microscope (TEM) images, X-ray diffraction (XRD), energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) analysis. Results show that the average size of nZVI is 49 nm and it has two layers. The outer layer (shell) is comprised of iron oxides (i.e. FeO) while the core is elemental iron (Fe). At pH 2, nZVI was found to be a good replacement for iron sulfate (FeSO4) as a ferrous iron (Fe2+) source in the sono-Fenton process. In addition, the removal process of organic pollutants from diluted palm oil mill effluent (POME) was also accelerated by ultrasound, particularly at higher intensity and longer sonication time. Eighty percent (80%) of the chemical oxygen demand (COD) was removed in 2 h instead of 24 h by silent degradation.

Activated alumina is a high surface area and highly porous form of aluminum oxide that can be employed for contaminant species adsorb from ether gases or liquids without changing its form. The research in getting this material has generated huge interested. Thus, this paper presented preparation of activated alumina from chemical process. Pure aluminum (99.9% pure) reacted at room temperature with an aqueous NaOH in a reactor to produce a solution of sodium aluminate (NaAlO2). This solution was passed through filter paper and the clear filtrate was neutralized with H2SO4, to pH 6, 7 or 8, resulting in the precipitation of a white gel, Al(OH)3·XH2O. The washed gel for sulfate ions were dried at 80 °C for 6 h, a 60 mesh sieve was to separate and sort them into different sizes. The samples were then calcined (burn) for 3h in a muffle furnace, in air, at a heating rate of 2 °C min–1. The prepared activated alumina was further characterized for better understanding of its physical properties in order to predict its chemical mechanism.

Fenton process is one of the advanced oxidation processes (AOPs) used to remove complex organic pollutants in wastewater. In this study, instead of iron sulfate (FeSO4), nano zero valent iron (nZVI) was used as a major source of ferrous iron (Fe 2+ ). In order to enhance the process, ultrasound was utilized in this study. Results show that, with the aid of ultrasound, nZVI produced more Fe 2+ compared to FeSO4 at pH 2. Furthermore, combination of higher intensity and longer sonication time in Fenton process acceleratde the chemical oxygen demand (COD) removal from palm oil mill effluent (POME). Through the process, 80% of COD content was removed within 2 hours instead of 24 hours of silent degradation.