Enhanced efficiency of AgAlO2/g-C3N4 binary composite to degrade organic pollutants for environmental remediation under visible light irradiation.

This study explores the utilization of semiconductor-based photocatalysts for environmental remediation through photocatalytic degradation, harnessing solar energy for effective treatment. The primary focus is on the application of photocatalytic technology for the degradation of 2-chlorophenol and methylene blue, critical pollutants requiring remediation. The research involves the synthesis of binary AgAlO2/g-C3N4 nanocomposites through an exchange ion method, subsequent calcination, and sonication. This process enhances the transfer of photogenerated electrons from AgAlO2 to g-C3N4, resulting in a significantly increased reductive electron charge on the surface of g-C3N4. The photocatalytic activity of the synthesized composites is comprehensively examined in the degradation of 2-chlorophenol and methylene blue through detailed crystallographic, electron-microscopy, photoemission spectroscopy, electrochemical, and spectroscopic characterizations. Among the various composites, AgAlO2/20% g-C3N4 emerges as the most active photocatalyst, achieving an impressive 98% degradation of methylene blue and 97% degradation of 2-chlorophenol under visible light. Notably, AgAlO2/20% g-C3N4 surpasses bare AgAlO2 and bare g-C3N4, exhibiting 1.66 times greater methylene blue degradation and constant rate (k) values of 20.17 × 10-3 min-1, 4.18 × 10-3 min-1 and 3.48 × 10-3 min-1, respectively. The heightened photocatalytic activity is attributed to the diminished recombination rate of electron-hole pairs. Scavenging evaluations confirm that O2•- and h+ are the primary photoactive species steering methylene blue photodegradation over AgAlO2/g-C3N4 in the visible region. These findings present new possibilities for the development of efficient binary photocatalysts for environmental remediation.

Long-term evaluation of palm oil mill effluent (POME) steam reforming over lanthanum-based perovskite oxides.

To replace the obsolete ponding system, palm oil mill effluent (POME) steam reforming (SR) over net-acidic LaNiO3 and net-basic LaCoO3 were proposed as the POME primary treatments, with promising H2-rich syngas production. Herein, the long-term evaluation of POME SR was scrutinized with both catalysts under the optimal conditions (600 °C, 0.09 mL POME/min, 0.3 g catalyst, & 74-105 µm catalyst particle size) to examine the catalyst microstructure changes, transient process stability, and final effluent evaluation. Extensive characterization proved the (i) adsorption of POME vapour on catalysts before SR, (ii) deposition of carbon and minerals on spent SR catalysts, and (iii) dominance of coking deactivation over sintering deactivation at 600 °C. Despite its longer run, spent LaCoO3 (50.54 wt%) had similar carbon deposition with spent LaNiO3 (50.44 wt%), concurring with its excellent coke resistance. Spent LaCoO3 (6.12 wt%; large protruding crystals) suffered a harsher mineral deposition than spent LaNiO3 (3.71 wt%; thin film coating), confirming that lower reactivity increased residence time of reactants. Transient syngas evolution of both SR catalysts was relatively steady up to 4 h but perturbed by coking deactivation thereafter. La2O2CO3 acted as an intermediate species that hastened the coke removal via reverse Boudouard reaction upon its decarbonation. La2O2CO3 decarbonation occurred continuously in LaCoO3 system but intermittently in LaNiO3 system. LaNiO3 system only lasted for 13 h as its compact ash blocked the gas flow. LaCoO3 system lasted longer (17 h) with its porous ash, but it eventually failed because KCl crystallites blocked its active sites. Relatively, LaCoO3 system offered greater net H2 production (72.78%) and POME treatment volume (30.77%) than LaNiO3 system. SR could attain appreciable POME degradation (>97% COD, BOD5, TSS, & colour intensity). Withal, SR-treated POME should be polished to further reduce its incompliant COD and BOD5.

Stably suspended SiO2-supported CdS photocatalyst for a promising organic pollutant degradation in the absence of mechanical stirring.

Even with solar-activatable photocatalyst, incommensurable energy input for stirring is still required to overcome the transport limitations in powder-photocatalysis. To counter this, a novel concept of auto-suspending photocatalyst based on SiO2/CdS was proposed to enable promising photo-activity even under stirring-free condition. Functionally-speaking, CdS would act as photoreaction-driver while SiO2 endows sufficient buoyance for suspension-stabilization during stirring-free photocatalysis. In photoreactions degrading methylene blue for theoretical demonstration, SiO2/CdS_0.3 promises only 4.57% activity reduction in non-stirred photoreaction, enabling 15.26% of methylene blue decolorization comparing to 15.99% of stirred-photoreaction under visible light irradiation. This could be ascribed to the slow settling tendency of SiO2/CdS_0.3, evading severe light-shielding under stacked condition. Also, its rightly-exposed SiO2 surface permits 'adsorb-and-degrade' mechanism, thereby overcoming the sluggish surface transport across thick boundary layer. Contrarily, photocatalyst with quintuple CdS content (SiO2/CdS_1.5) exhibits largest activity reduction (31.47%), reasoned by its quick-settling tendency. Overall, current study provides new perspectives to photocatalysis-community. The success elimination of mechanical stirring from photocatalysis promises significant energy-saving (19.1-136 kW/m3), thus consenting better practicality for solar energy-harvesting and environmental protection.

Instant Formulation of Inhalable Beclomethasone Dipropionate-Gamma-Cyclodextrin Composite Particles Produced Using Supercritical Assisted Atomization.

Medical composites derived from Gamma-cyclodextrin (γ-CD) and beclomethasone dipropionate-gamma-cyclodextrin (BDP-γ-CD) are synthesized over supercritical-assisted atomization (SAA) herein. Carbon dioxide, which serves the dual function of spraying medium and co-solute, is incorporated in this process along with the ethanolic solvent. Results indicate that, for fine spherical particles, optimized aerosol performance could be obtained with 50.0% (w/w) ethanolic solvent, precipitator, and saturator at 373.2 K and 353.2 K, respectively, and carbon dioxide-to-γ-CD flow ratio of 1.8 in the presence of 10 wt% leucine (LEU) as dispersion enhancer. It is also noted that γ-CD solution at low concentration typically renders better aerosol performance of the particles. During drug particle-derivation, the solubility of drug BDP elevated considerably due to the formation of inclusion complexes, further assisted by the ethanolic solvent which increases the lipophilicity of BDP. Meanwhile, the in vitro aerosolization and dissolution performance of drug composites derived from varied γ-CD-to-BDP mass ratio (Z) were also evaluated. It was found that high Z promises higher fine particle fraction in the obtained drug composite while the dissolution rate of active ingredient (BDP) exhibits positive correlation to the content of water-soluble excipient (γ-CD) in the formulation. This study offers a new avenue for instant drug formulation with promising pulmonary delivery over the SAA technique.

Hydrothermal synthesis temperature induces sponge-like loose silica structure: A potential support for Fe2O3-based adsorbent in treating As(V)-contaminated water.

Low cost Fe2O3-based sorbents with an exceptional selectivity toward the targeted As(V) pollutant have gained extensive attention in water treatment. However, their structural features often influence removal performance. In this respect, we present herein a rational design of silica-supported Fe2O3 sorbents with an enhanced morphological structure based on a simple temperature-induced process. Low-hydrothermal temperature synthesis (60 and 100 °C) provided a large silica-cluster size with a close packed structure (S-60 and S-100), contributing to an increase in mass transport resistance. Fe2O3/S-60 with 6.2-nm pore width silica achieved a maximum As(V) uptake capacity (qm) of only 3.5 mg g-1. Supporting Fe2O3 on S-100 with an approximately two-fold increase in the pore size (13 nm) did not lead to any evident enhancement in qe (3.7 mg g-1). However, expanding the pore window up to 22.6 nm (S-140) and 39.5 nm (S-180), along with changing from close-packed to sponge-like loose structures induced by high-temperature synthesis (140 °C and 180 °C), resulted in substantial increases in qm. Fe2O3/S-140 had 1.7 and 1.6 times higher qm (5.9 mg g-1) than Fe2O3/S-100 and Fe2O3/S-60, respectively. The highest qm (7.4 mg g-1) was achieved for Fe2O3/S-180, which was attributed to its relatively small-sized silica cluster and the largest cavities that facilitated easier access by As(V) to adsorbing sites.

Cross-redox and simultaneous removal of Cr(VI) and As(III): Influences of Fe(II), Fe(III), oxalic acid, and dissolved organic carbon.

Hexavalent chromium [Cr(VI)] and arsenite [As(III)] are hazardous to both human and ecosystem. While their cross-redox reaction decreases both their toxicities, the interferences from ubiquitous substances like Fe (Fe(II) and Fe(III)) and organic compounds (oxalic acid and soil-extracted dissolved organic carbon (DOC)) on such interaction are rarely reported; thence, inspires the investigation in this study. Results showed that the cross-redox, in the absence of interfering substances, only occurred at pH≤2.0, with reaction orders of 0.676 and 0.783 in respect to the concentration of Cr(VI) and As(III). The pseudo-reaction constant, k', of such reaction was recorded at 0.087 m1.377/(mmol0.459 min). With the addition of Fe(II), the rate of Cr(VI) reduction is promoted in conjunction with suppressed As(III) oxidation. Upon neutralizing to pH 6.0, such reduced Cr can be entirely removed via Fe(II)-assisted adsorption and/or co-precipitation. Meanwhile, the elimination of aqueous As is relatively inferior (36 %), attributed to the largely preserved As(III), which is less susceptible to adsorptive/co-precipitative removal. Unlike Fe(II), Fe(III) did not alter Cr(VI)-As(III) cross-redox path, but triggered high adsorptive and/or co-precipitative removals of Cr and As (90 %). In contrast, both organically-altered systems exhibits plummeted As(III) oxidation, under distinctive mechanisms: oxalic acid competes with As(III) in the redox interactions while DOC reduces As(V) into As(III). Also, DOC would undergo complexion with metals and/or blocked the adsorption or co-precipitation sites, leading to even lower Cr and As precipitation. This study unravelled the interference from ubiquitous species in the co-removal of Cr(VI) and As(III), which provides insightful remediation for heavy metal contaminations.

Flexible and Highly Conductive Textiles Induced by Click Chemistry for Sensitive Motion and Humidity Monitoring.

To date, multifunctional sensors have aroused widespread concerns owing to their vital roles in the healthcare area. However, there are still significant challenges in the fabrication of functionalized integrated devices. In this work, hydrophobic-hydrophilic patterns are constructed on polyester-spandex-blended knitted fabric surface by the chemical click method, enabling accurate deposition of functionalized materials for sensitive and stable motion and humidity sensing. Representatively, a conductive silver nanowire (Ag NW) network was deliberately deposited on only the designated hydrophilic fabric surface to realize accurate, repeatable, and stable motion sensing. Such a Ag NWs sensor recorded a low electrical resistance (below 60 Ω), stable resistance cycling response (over 2000 cycles), and fast response time to humidity (0.46 s) during the sensing evaluation. In addition to experimental sensing, real human motions, such as mouth-opening and joint-flexing (wrist and neck), could also be detected using the same sensor. Similar promising outputs were also obtained over the humidity sensor fabricated over the same chemical click method, except the sensing material was replaced with polydopamine-modified carboxylated carbon nanotubes. The resultant sensor exhibits excellent sensitivity to not only experimentally adjusted environment humidity but also to the moisture content of breath and skin during daily activities. On top of all these, both sensors were fabricated over highly flexible fabric that offers high wearability, promising great application potential in the field of healthcare monitoring.

Facile preparation of tremella-like TiO2/Cd:ZnIn2S4 photoanode with enhanced photo-electro-chemical (PEC) performance for energy and environmental applications.

The realization of solar-driven photoelectrochemical (PEC) process lies in the success development of materials with excellent photoelectric properties. Past reports identified TiO2, upon modified with both Cd and ZnIn2S4 (ZIS), exhibits promising PEC performance; however, at the cost of tedious preparation. In view of this, our work proposes a facile one-step hydrothermal strategy to deposit both modifiers onto the pre-obtained TiO2 nanotubes (NTs), realizing rose-like TiO2/ZnIn2S4 (TiO2/ZIS) or tremella-like TiO2/Cd:ZnIn2S4 (TiO2/Cd:ZIS) with improved PEC performances. Interestingly, the thickness of ZIS petals, which deposited on top of TiO2 NTs, is positively-correlated to its Cd-composition, signifying the substitutional doping of Cd into the unit cell of ZIS. This renders robust ionic interactions between the constituents, prompting the enhanced optical properties of TiO2 in conjecture to its reduced impedance. As a result, the recombination rate of photo-electric-derived carriers was drastically suppressed, with an improved photocurrent density of 606.2 µA cm-2 recorded by TiO2/Cd:ZIS photoanode under solar irradiation. Such performance is 80 times and 5.16 times higher than those of bare TiO2 NTs and TiO2/ZIS counterparts. The photoconversion efficiencies in terms of incident photon-to-current conversion efficiency (IPCE) and applied bias photon current efficiency (ABPE) for TiO2/Cd:ZIS were significantly improved too, recorded at 1.12% and 0.38%, respectively, under standard evaluation condition. As summary, our work proposes a facile one-step hydrothermal approach that simultaneously-deposit both Cd and ZIS onto TiO2 photoanode for an enhanced PEC performance. This opens up a wider horizon for PEC technology, further unlocking its potential in both energy and environmental applications.

Biomass-derived carbon-based and silica-based materials for catalytic and adsorptive applications- An update since 2010.

Biomass, which defined as plant- or animal-based materials, is intriguing tremendous scientific attentions due to its renewable attribute in serving energy security. Amongst, the plant-based biomasses, particularly those that co-generated in the agriculture activities, are commonly regarded as fuel for burning, which overlooked their hidden potentials for high-end applications. Organically, the plant-based biomass constitutes of lignocellulose components, which can be served as promising precursors for functionalized carbon materials. Meanwhile, its inorganic counterpart made up of various minerals, with Si being the most concerned one. With the advancement of biomass technologies and material synthesis in recent years, numerous attempts were endeavoured to obtain valorised products from biomass. Particularly, syntheses of catalytic and adsorptive materials are actively researched in the field of biomass reutilization. Herein, our work systematically summarized the advancements of biomass-materials for these applications in recent 10 years (2010-2020), with a special focus on the carbon-based and Si-based catalytic/adsorptive materials. Significantly, the deriving steps, inclusive of both pre-treatment and post-treatment of such materials, are incorporated in the discussion, alongside with their significances revealed too. The performance of the as-obtained materials in the respective application is systematically correlated to their physicochemical properties, hence providing valuable insights to the readers. Challenges and promising directions to be explored are raised too at the end of the review, aiming to advocate better-usage of biomass while offering great opportunities to sustain catalysis and adsorption in the industrial scale.

A review on dry-based and wet-based catalytic sulphur dioxide (SO2) reduction technologies.

While sulphur dioxide (SO2) is known for its toxicity, numerous effective countermeasures were innovated to alleviate its hazards towards the environment. In particular, catalytic reduction is favoured for its potential in converting SO2 into harmless, yet marketable product, such as elemental sulphur. Therefore, current review summarises the critical findings in catalytic SO2 reduction, emphasising on both dry- and wet-based technology. As for the dry-based technology, knowledge related to SO2 reduction over metal-, rare earth- and carbon-based catalysts are summarised. Significantly, both the reduction mechanisms and important criteria for efficient SO2 reduction are elucidated too. Meanwhile, the wet-based SO2 reduction are typically conducted in reactive liquid medium, such as metal complexes, ionic liquids and organic solvents. Therefore, the applications of the aforesaid liquid mediums are discussed thoroughly in the similar manner to dry-technology. Additionally, the pros and cons of each type of catalyst are also presented to provide valuable insights to the pertinent researchers. Finally, some overlooked aspects in both dry- and wet-based SO2 reduction are identified, with potential solutions given too. With these insights, current review is anticipated to contribute towards practicality improvement of catalytic SO2 reduction, which in turn, protects the environment from SO2 pollution.

Microbial fuel cells for bioelectricity production from waste as sustainable prospect of future energy sector.

Microbial fuel cell (MFC) is lauded for its potentials to solve both energy crisis and environmental pollution. Technologically, it offers the capability to harness electricity from the chemical energy stored in the organic substrate with no intermediate steps, thereby minimizes the entropic loss due to the inter-conversion of energy. The sciences underneath such MFCs include the electron and proton generation from the metabolic decomposition of the substrate by microbes at the anode, followed by the shuttling of these charges to cathode for electricity generation. While its promising prospects were mutually evinced in the past investigations, the upscaling of MFC in sustaining global energy demands and waste treatments is yet to be put into practice. In this context, the current review summarizes the important knowledge and applications of MFCs, concurrently identifies the technological bottlenecks that restricted its vast implementation. In addition, economic analysis was also performed to provide multiangle perspectives to readers. Succinctly, MFCs are mainly hindered by the slow metabolic kinetics, sluggish transfer of charged particles, and low economic competitiveness when compared to conventional technologies. From these hindering factors, insightful strategies for improved practicality of MFCs were formulated, with potential future research direction being identified too. With proper planning, we are delighted to see the industrialization of MFCs in the near future, which would benefit the entire human race with cleaner energy and the environment.

Coupled porosity and heterojunction engineering: MOF-derived porous Co3O4 embedded on TiO2 nanotube arrays for water remediation.

Strive to develop the interaction and efficient co-catalysts is one of the vital projects in realizing hybrid photocatalytic systems for water remediation. In this work, p-type porous Co3O4 was embedded onto n-type vertical TiO2 nanotube via an in-situ thermal etching method. ZIF-67 was employed as the structural template for Co3O4, which then augmented the light harvesting ability of the resultant photocatalyst. Such improvement was prompted by the light reflecting and directing attributes of porous Co3O4. Therefore, a remarkable MB removal rate was attained under sunlight irradiation, with superoxide radical being identified as the major reactive species. Photoelectric properties evaluation also verified that the p-n heterojunction developed herein exhibits outstanding charges separation ability with low impedance, particularly under light irradiation. This work highlights the idea on coupling both porous and p-n heterojunction engineering in augmenting photoactivity of catalyst, while offering insights in such structure-mediating approach.

Adoption of TiO2-photocatalysis for palm oil mill effluent (POME) treatment: Strengths, weaknesses, opportunities, threats (SWOT) and its practicality against traditional treatment in Malaysia.

The technical feasibility of TiO2-photocatalysis towards palm oil mill effluent (POME) treatment is well-proven in previous studies. As a continuity, current study evaluated the strengths, weaknesses, opportunities and threats (SWOT) in a concise manner, subsequently discussed its practicality in palm oil industry of Malaysia. Indeed, TiO2-photocatalysis displays a promising technical feasibility in treating POME, but its wide application is economically-suppressed. It is positing that biological-based treatments (including the existing open-ponding system) are more likely to be employed as the major treating approach for POME over TiO2-photocatalysis. This is particularly true as biological-based treatments offer better performance index for concentrated POME with comparatively lower treatment cost and technicality needed. Furthermore, it is also prevailed with high biogas generability, therefore being irreplaceably benchmarked for POME treatment in Malaysia. Instead of replacing biological treatment entirely, the adoption of TiO2-photocatalysis as complementing tertiary treatment for biological-treated-POME is more practical, bestowed to its robust organic-mineralizing feature for low concentration POME. Such integrated system is expected to augment the POME degradation efficiency, hence effectively preserve the environment from POME pollution.

Photocatalytic remediation of organic waste over Keggin-based polyoxometalate materials: A review.

Photocatalytic remediation of industrial water pollution has courted intense attention lately due to its touted green approach. In this respect, Keggin-based polyoxometalates (POMs) as green solid acids in photocatalytic reaction possess superior qualities, viz. unique photoinduced charge-transfer properties, strong photooxidative-photoreductive ability, high chemical and thermal stability, and so forth. Unfortunately, it suffers from a large bandgap energy, low specific surface area, low recoverability, and scarce utilization in narrow absorption range. Therefore, the pollutant degradation performance is not satisfactory. Consequently, multifarious research to enhance the photocatalytic performance of Keggin-based POMs were reported, viz. via novel modifications and functionalizations through a variety of materials, inclusive of, inter alia, metal oxides, transition metals, noble metals, and others. In order to advocate this emerging technology, current review work provides a systematic overview on recent advancement, initiated from the strategized synthetic methods, followed by hierarchical enhancement and intensification process, at the same time emphasizes on the fundamental working principles of Keggin-based POM nanocomposites. By reviewing and summarizing the efforts adopted global-wide, this review is ended with providing useful outlooks for future studies. It is also anticipated to shed light on producing Keggin-based POM nanocomposites with breakthrough visible- and solar-light-driven photocatalytic performance against recalcitrant organic waste.

Elimination of energy-consuming mechanical stirring: Development of auto-suspending ZnO-based photocatalyst for organic wastewater treatment.

Powdered-photocatalysis of organic wastewater is widely investigated, unfortunately not industrially implemented due to its high energy requirement. Interestingly, such issue may be alleviated via the elimination of mechanical stirring required. Core-shell ZnO-based photocatalysts were developed herein, subsequently demonstrated efficient photocatalytic activities in the absence of mechanical stirring. Results show that the developed SiO2-cored ZnO photocatalyst are highly crystalline, while significantly smaller than coreless, pure ZnO due to the multi-point crystallization prompted. Additionally, it is also inherited with considerable buoyancy ability from SiO2-core in the absence of mechanical stirring, concurrently rendered with UV-active properties due to its ZnO-shell. Experimentally, 55% of particles of ZnO_0.0025 (0.0025 mol of ZnO-deposition) were found stably suspended for 60 min in liquid substrate, as opposed to the instant-settling of pure ZnO particles. In term of photocatalytic activity, ZnO_0.01 manifested the best methylene blue (MB) degradation with 150 mL/min of O2-bubbling. 67.63% of MB was degraded with photocatalyst loading of 0.2 g/L after 120 min UV-irradiation, simultaneously recorded the highest pseudo-first order reaction constant of 9.636 × 10-3 min-1. As summary, the auto-suspending photocatalysis conceptualized in current study offers a high possibility in reducing energy requirement for photo-treatment of wastewater, hence advocating its industrialization potential in near future.

Integration of machine learning-based prediction for enhanced Model's generalization: Application in photocatalytic polishing of palm oil mill effluent (POME).

In predicting palm oil mill effluent (POME) degradation efficiency, previous developed quadratic model quantitatively evaluated the effects of O2 flowrate, TiO2 loadings and initial concentration of POME in labscale photocatalytic system, which however suffered from low generalization due to the overfitting behaviour. Evidently, high RMSE (131.61) and low R2 (-630.49) obtained indicates its insufficiency in describing POME degradation at unseen factor ranges, hence verified the fact of poor generalization. To overcome this issue, several models were developed via machine learning-assisted techniques, namely Gaussian Process Regression (GPR), Linear Regression (LR), Decision Tree (DT), Supported Vector Machine (SVM) and Regression Tree Ensemble (RTE), subsequently being assessed systematically. To achieve high generalization, all models were subjected to 'train-all-test-all' strategy, 5-fold and 10-fold cross validation. Specifically, GPR model was furnished with high accuracy in 'train-all-test-all' strategy, judging from its low RMSE (1.0394) and high R2 (0.9962), which however menaced by the risk of overfitting. In contrast, despite relatively poorer RMSE and R2 (1.7964 and 0.9886) obtained in 5-fold cross validation, GPR model was rendered with highest generalization, while sufficiently preserving its accuracy in development process. Besides, SVM and RTE models were also demonstrated promising R2 (0.9372 and 0.9208), which however shadowed by their high RMSEs (4.2174 and 4.7366). Furthermore, the extraordinary generalization of GPR model was coincidentally verified in 10-fold cross validation. The lowest RMSE (2.1624) and highest R2 (0.9835) obtained with feature number of 36 asserted its sufficiency in both generalization and accuracy prospect. Other models were all rendered with slight lower R2 (> 0.9), plausibly due to the higher RMSE (> 4.0). According to GPR model, optimized POME degradation (52.52%) can be obtained at 70 mL/min of O2, 70.0 g/L of TiO2 and 250 ppm of POME concentration, with only ∼3% error as compared to the actual data.

Facile synthesis of CaFe2O4 for visible light driven treatment of polluting palm oil mill effluent: Photokinetic and scavenging study.

In this paper, a facile synthesis method for CaFe2O4 is introduced that produces a catalyst capable of significant photocatalytic degradation of POME under visible light irradiation. The co-precipitation method was used to produce two catalysts at calcination temperatures of 550 °C and 700 °C dubbed CP550 and CP700. CP550 demonstrated the maximum COD removal of 69.0% at 0.75 g/L catalyst loading after 8 h of visible light irradiation which dropped to 61.0% after three consecutive cycles. SEM images indicated that the higher calcination temperature of CP700 led to annealing which reduced the pore volume (0.025 cm3/g) and pore diameter (10.3 nm) while simultaneously creating a smoother and more spherical surface with lower SBET (9.73 m2/g). In comparison, CP550 had a rough hair-like surface with higher SBET (27.28 m2/g) and pore volume (0.077 cm3/g) as evidenced by BET analysis. XRD data indicated the presence of CaFe5O7 in the CP550 composition which was not present in CP700. The presence of Wustite-like FeO structures in CaFe5O7 are likely the cause for lower photoluminescence intensity profile and hence better charge separation of CP550 as these structures in CaFe2O4 have been known to increase resistivity and electron localization. The COD removal of CP550 dropped from 69.0% to just 7.0% upon adding a small quantity of isopropanol into the reaction mixture indicating hydroxyl radicals as the primary reactive oxidative species.

Restoration of liquid effluent from oil palm agroindustry in Malaysia using UV/TiO2 and UV/ZnO photocatalytic systems: A comparative study.

In this study, we have employed a photocatalytic method to restore the liquid effluent from a palm oil mill in Malaysia. Specifically, the performance of both TiO2 and ZnO was compared for the photocatalytic polishing of palm oil mill effluent (POME). The ZnO photocatalyst has irregular shape, bigger in particle size but smaller BET specific surface area (9.71 m2/g) compared to the spherical TiO2 photocatalysts (11.34 m2/g). Both scavenging study and post-reaction FTIR analysis suggest that the degradation of organic pollutant in the TiO2 system has occurred in the bulk solution. In contrast, it is necessary for organic pollutant to adsorb onto the surface of ZnO photocatalyst, before the degradation took place. In addition, the reactivity of both photocatalysts differed in terms of mechanisms, photocatalyst loading and also the density of photocatalysts. From the stability test, TiO2 was found to offer higher stability, as no significant deterioration in activity was observed after three consecutive cycles. On the other hand, ZnO lost around 30% of its activity after the 1st-cycle of photoreaction. The pH studies showed that acidic environment did not improve the photocatalytic degradation of the POME, whilst in the basic environment, the reaction media became cloudy. In addition, longevity study also showed that the TiO2 was a better photocatalyst compared to the ZnO (74.12%), with more than 80.0% organic removal after 22 h of UV irradiation.

Optimization of photocatalytic degradation of palm oil mill effluent in UV/ZnO system based on response surface methodology.

This paper reports on the optimization of palm oil mill effluent (POME) degradation in a UV-activated-ZnO system based on central composite design (CCD) in response surface methodology (RSM). Three potential factors, viz. O2 flowrate (A), ZnO loading (B) and initial concentration of POME (C) were evaluated for the significance analysis using a 23 full factorial design before the optimization process. It is found that all the three main factors were significant, with contributions of 58.27% (A), 15.96% (B) and 13.85% (C), respectively, to the POME degradation. In addition, the interactions between the factors AB, AC and BC also have contributed 4.02%, 3.12% and 1.01% to the POME degradation. Subsequently, all the three factors were subjected to statistical central composite design (CCD) analysis. Quadratic models were developed and rigorously checked. A 3D-response surface was subsequently generated. Two successive validation experiments were carried out and the degradation achieved were 55.25 and 55.33%, contrasted with 52.45% for predicted degradation value.