Mn-doped Zn/Al layered double hydroxides as photocatalysts for the 4-chlorophenol photodegradation

Morales-Mendoza, G.,Tzompantzi, F.,Garcia-Mendoza, C.,Lopez, R.,De la Luz, V.,Lee, S.W.,Kim, T.H.,Torres-Martinez, L.M.,Gomez, R. Elsevier 2015 Applied clay science Vol.118 No.-

Mn-doped Zn/Al layered double hydroxides (LDH) with Mn 0.5-3.0% mol respect to Zn content with improved photocatalytic degradation of 4-chlorophenol (4Clphenol) were studied. The characterization studies showed the isomorphic incorporation Mn as dopant until 1% mol. The 4Clphenol degradation was proposed as result of a combined effect of oxidation by both hydroxyl radicals (OH?) and photogenerated holes (h<SUP>+</SUP>). In a proposed mechanism it is suggested that Mn enhances the charge separation acting as electron e<SUP>-</SUP> (Mn<SUP>3+</SUP>; Mn<SUP>4+</SUP>) or hole h<SUP>+</SUP> (Mn<SUP>2+</SUP>; Mn<SUP>3+</SUP>) traps according to its oxidation state. Exhaustive characterization through EDS, XRD, UV-vis-DRS, TEM-Dark field STEM, fluorescence spectroscopy for OH? detection and XPS, has been done denoting the importance of the Mn content and its different oxidation states in the photophysical and photocatalytic properties of the Mn-doped Zn/Al-based layered double hydroxides.

Political Dynasties and Terrorism: An Empirical Analysis Using Data on the Philippines

Ronald U. Mendoza,Jurel K. Yap,Gabrielle Ann S. Mendoza,Angelika Lourdes J. Pizarro,Georgi Engelbrecht 서울대학교 통일평화연구원 2022 Asian Journal of Peacebuilding Vol.10 No.2

Political inequality may cultivate grievances against the government and eventuallyprovoke conflict. In the Philippines, this is reflected in the prevalence of politicaldynasties. Often these dynasties face deep conflicts of interest as they prioritizeclientelist ties over the public good, and act as bosses in their local constituencies. Through regression analysis, this paper finds robust statistical evidence that twoout of three measures of political dynasty persistence are positively associatedwith political violence. Results suggest that a concentration of power leads toweaker governance and worse development outcomes, excludes critical sectors,and ultimately provokes political violence. The study emphasizes the importanceof promoting checks and balances for more inclusive and peaceful development inemerging democracies such as the Philippines.

Photocatalytic removal of dissolved metals using nanoparticle-coated zeolite media filters

Mendoza, Joseph Albert,Kang, Joo-Hyon 한국방재학회 2015 한국방재학회 학술발표대회논문집 Vol.14 No.-

Storm water pollution has been the various concerns over the past decade. Decreasing the contamination levels of runoffs to the minimum accepted levels to protect the water quality of rivers, estuaries, streams, lakes, seas, and other bodies of waters have been the objectives of various storm water best management practices (BMP) implemented. BMPs has been augmented to existing water treatment facilities to provide additional resources for potable water usage. Novel filter materials are used to improve the performance of media filters and extend their capabilities to removing other pollutants such as organic/aromatic hydrocarbons and heavy metals. Among the novel materials being considered are photocatalyst nanoparticles coated into the sand media filter. Photocatalysts have been applied in the degradation of organic pollutants with the help of visible light irradiation. This paper describes the synthesis and use of nanoparticle–coated zeolite media filter to remove dissolved metals (Cu and Zn). Catalyst surface analysis revealed that the Cu and Zn were chemically adsorbed, and were transformed into its corresponding elemental forms.

Pulse electrodeposited PtSn electrocatalyst on a PEDOT/graphene-based electrode for ethanol oxidation in an acidic medium

Mendoza, Maria Krisandra L.,Tongol, Bernard John V.,Shanmugam, Sangaraju,Kim, Hasuck Elsevier 2018 International journal of hydrogen energy Vol.43 No.43

<P><B>Abstract</B></P> <P>Pulse electrodeposition of Pt and Sn using 10 mM H<SUB>2</SUB>PtCl<SUB>6</SUB>⋅6H<SUB>2</SUB>O in 0.10 M H<SUB>2</SUB>SO<SUB>4</SUB> and 10 mM SnCl<SUB>2</SUB>⋅2H<SUB>2</SUB>O in 0.10 M HCl was conducted on a support matrix consisting of electropolymerized poly (3,4-ethylenedioxythiophene) (PEDOT) and electrochemically exfoliated graphene oxide (EGO). The Field Emission – Scanning Electron Microscopy (FE-SEM) studies of PtSn/PEDOT/EGO (i.e., PEDOT on EGO) showed a homogeneous globular composite, while PtSn/EGO/PEDOT (i.e., EGO on PEDOT) revealed a heterogeneous composite with wrinkled and globular surface morphologies. An Energy Dispersive X-ray (EDX) analysis (as a percentage of Pt and Sn) of PtSn/PEDOT/EGO is in agreement with the X-ray Photoelectron Spectroscopy (XPS) analysis, indicative of a homogeneous surface for the dispersion of metallic particles. However, the EDX and XPS analyses of PtSn/EGO/PEDOT showed variations in the amount of Pt and Sn, indicative of possible mixing of the EGO and PEDOT support matrices. Cyclic voltammetry (CV) and chronoamperometry using 1.0 M ethanol in 0.1 M H<SUB>2</SUB>SO<SUB>4</SUB> demonstrated higher electrocatalytic activity (83.7 mA/cm<SUP>2</SUP>) and electrochemical stability (29.0% current retention) in PtSn/PEDOT/EGO than PtSn/EGO/PEDOT.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PtSn was pulse electrodeposited on PEDOT/EGO and EGO/PEDOT support matrices. </LI> <LI> PEDOT/EGO is a better support matrix for the pulse electrodeposited PtSn. </LI> <LI> PtSn/PEDOT/EGO showed a more enhanced electrocatalytic activity and stability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Photocatalytic removal of gaseous nitrogen oxides using WO₃/TiO₂ particles under visible light irradiation: Effect of surface modification

Mendoza, Joseph Albert,Lee, Dong Hoon,Kang, Joo-Hyon Elsevier 2017 CHEMOSPHERE - Vol.182 No.-

<P><B>Abstract</B></P> <P>Photocatalytic nanoparticles have been receiving considerable attention for their potential use in many environmental management applications, including urban air quality control. This paper investigates the performance of surface modified WO<SUB>3</SUB>/TiO<SUB>2</SUB> composite particles in removing gaseous nitrogen oxides (NO<SUB>x</SUB>) under visible light irradiation. The WO<SUB>3</SUB>/TiO<SUB>2</SUB> composite particles were synthesized using a modified wet chemical method with different concentrations of NaOH solution used as a surface modification agent for the host TiO<SUB>2</SUB> particles. The NO<SUB>x</SUB> removal efficiency of the WO<SUB>3</SUB>/TiO<SUB>2</SUB> particles was evaluated using a lab–scale continuous gas flow photo-reactor with a gas contact time of 1 min. Results showed that surface modification using NaOH can enhance the photocatalytic activity of the WO<SUB>3</SUB>/TiO<SUB>2</SUB> particles. The NO<SUB>x</SUB> removal efficiency of the surface modified WO<SUB>3</SUB>/TiO<SUB>2</SUB> was greater than 90%, while that of WO<SUB>3</SUB>/TiO<SUB>2</SUB> particles prepared by the conventional wet chemical method was ∼75%. The enhanced removal efficiency might be attributed to the formation of oxygen vacancies on the TiO<SUB>2</SUB> surface, providing sites for WO<SUB>3</SUB> particles to effectively bind with TiO<SUB>2</SUB>. However, excess amount of NaOH >3 M deteriorated the photocatalytic performance due to the increased agglomeration of the host TiO<SUB>2</SUB> particles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The visible light active WO<SUB>3</SUB>/TiO<SUB>2</SUB> particles were surface modified by NaOH. </LI> <LI> Surface modification increased dispersion of WO<SUB>3</SUB> particles on the TiO<SUB>2</SUB> surface. </LI> <LI> Surface modified WO<SUB>3</SUB>/TiO<SUB>2</SUB> substantially enhanced the removal efficiency of NO<SUB>x</SUB>. </LI> <LI> Optimal concentration of NaOH should be used to avoid excessive sintering. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

The Philippine Society of Soil Science and Technology

Mendoza, D.M. 한국토양비료학회 2009 한국토양비료학회 학술발표회 초록집 Vol.2009 No.10

Structural improvements on hydrodynamic separators: a computational fluid dynamics approach

Mendoza, Joseph Albert,Lee, Dong Hoon,Lee, Sang-Il,Kang, Joo-Hyon IWA Publishing 2016 Water Science & Technology Vol.74 No.12

<P>Hydrodynamic separators (HDSs) have been used extensively to reduce stormwater pollutants from urbanized areas before entering the receiving water bodies. They primarily remove particulates and associated pollutants using gravity settling. Two types of HDSs with different structural configurations of the inner vortex-inducing components were presented in this study. One configuration consisted of a dip cylindrical plate with a center shaft while the other one has a hollow screen inside. With the help of computational fluid dynamics, the performance of these different types of HDSs have been evaluated and comparatively analyzed. The results showed that the particle removal efficiency was better with the cylindrical plate type HDSs than the screen type HDSs because of the larger swirling flow regime formed inside the device. Plate type HDSs were found more effective in removing fine particles (∼50 μm) than the screen type HDSs that were only efficient in removing large particles (≥250 μm). Structural improvements in a HDS such as increase in diameter and angle of the inlet pipe can enhance the removal efficiencies by up to 20% for plate type HDS while increase in the screen diameter can increase removal efficiencies of the screen type HDS.</P>

Photocatalytic performance of TiO2 and WO3/TiO2 nanoparticles coated on urban green infrastructure materials in removing nitrogen oxide

Mendoza, J. A.,Lee, D. H.,Kim, L.-H.,Kim, I. H.,Kang, J.-H. Springer-Verlag 2018 International journal of environmental science and Vol.15 No.3

<P>This study investigated the performance of UV light active TiO2 and UV-visible light active WO3/TiO2 nanoparticles as air purifying materials that can be potentially applied to urban green infrastructures such as rain gardens and pervious pavements. Using a laboratory-scale continuous gas flow photoreactor, the removal efficiency of gaseous nitrogen oxide (NO (x) ) by two different photocatalytic nanoparticles coated on natural zeolites and pervious concrete blocks was evaluated. The results showed that the TiO2- and WO3/TiO2-coated zeolites are excellent photoactive materials providing enhanced air purification function (similar to 95% removal efficiency of NO (x) ) under UV and UV-visible light irradiation, respectively. In contrast, both of the TiO2- and WO3/TiO2-coated pervious concrete blocks showed a measurable NO (x) removal (similar to 60%) only under UV irradiation, whereas the visible light activity of the WO3/TiO2-coated concrete block was significantly reduced (similar to 20%) mainly due to the decrease in the photocatalytic reaction sites for visible light. This study revealed the potential utility of photocatalytic nanoparticles in improving urban air quality, in the form of the surface component of various urban infrastructures.</P>

The benefit of one cannot replace the other: seagrass and mangrove ecosystems at Santa Fe, Bantayan Island

Mendoza, Ayana Rose R.,Patalinghug, Jenny Marie R.,Divinagracia, Joshua Ybanez The Ecological Society of Korea 2019 Journal of Ecology and Environment Vol.43 No.2

Background: In the Philippines, the practice of planting mangroves over seagrass has been a practice done to promote coastline protection from damages done by storms. Despite the added protection to the coastline, the addition of an artificial ecosystem gradually inflicts damage to the ecosystem already established. In this study, seagrass communities that had no history of mangrove planting were compared with those that had mangrove planting. The percent substrate cover of seagrass in the sampling areas was determined, and the macroinvertebrates present in the sampling areas were also observed. The study was conducted based on reports of mangrove planting activity that disrupted seagrass functions on Santa Fe, Bantayan Island, Cebu. Transect-quadrat method sampling was done to assess the chosen sites. Results: Six species of seagrass was found on the site without mangrove planting which was barangay Ocoy (Cymodocea sp., Thalassia sp., Halodule sp., Enhalus sp., Halophila sp., and Syringodium sp.) and had a higher percent cover, while only four were found on the site with mangrove planting (barangay Marikaban). It was also found that barangay Marikaban had a lesser Shannon-Wiener and Simpson's index compared to barangay Ocoy. Jaccard's index of similarity between the two sites was low. Conclusion: With the results of the assessment, we recommend proper monitoring of future mangrove planting activities and that these activities should not disrupt another ecosystem as all ecosystems are important.

An Overview of Southeast Asian Area Studies in the Philippines

Mendoza, Meynardo P. Korea Institute for ASEAN Studies 2017 Suvannabhumi Vol.9 No.1

In spite of being one of the first countries in Asia to establish an institution devoted to the study of the Asian region, area studies in the Philippines has languished over the years. In contrast, area studies programs of her neighbors have grown by leaps and bounds, invigorated by both public and private support. This observation becomes more glaring as Filipino scholars have made a name for themselves in the field of Southeast Asian Studies abroad. The paper is an appraisal of the current state of Southeast Asian area studies and the extent of its operation by the Philippines' top four universities, namely: the Asian Center of the University of the Philippines, the Ateneo de Manila University, the De La Salle University, and the University of Santo Tomas. Starting from the inception of area studies in the mid-1950s leading to a template patterned after the North American - European model, the paper then describes the challenges and its decline in the 80s toward its progression on a paradigm defined by the growing importance of, and actors within, the region. The paper expresses the view that one, the role of the government was both a boon and a bane in the development of area studies; and two, that the rapid economic growth and immense integration in the region in the last two decades gave a new impetus to Southeast Asian area studies, an enormous opportunity to capitalize on for Philippine universities.