Enhanced photocatalytic activity of graphene-TiO2 composite under visible light irradiation

N.R. Khalid,E. Ahmed,Zhanglian Hong,L. Sana,M. Ahmed 한국물리학회 2013 Current Applied Physics Vol.13 No.4

Novel grapheneeTiO2 (GReTiO2) composite photocatalysts were synthesized by hydrothermal method. During the hydrothermal process, both the reduction of graphene oxide and loading of TiO2nanoparticles on graphene were achieved. The structure, surface morphology, chemical composition and optical properties of composites were studied using XRD, TEM, XPS, DRS and PL spectroscopy. The absorption edge of TiO2 shifted to visible-light region with increasing amount of graphene in the composite samples. The photocatalytic degradation of methyl orange (MO) was carried out using grapheneeTiO2 composite catalysts in order to study the photocatalytic efficiency. The results showed that GReTiO2 composites can efficiently photodegrade MO, showing an enhanced photocatalytic activity over pure TiO2 under visible-light irradiation. The enhanced photocatalytic activity of the composite catalysts might be attributed to great adsorptivity of dyes, extended light absorption range and efficient charge separation due to giant p-conjugation system and two-dimensional planar structure of graphene.

Nitrogen doped TiO2 nanoparticles decorated on graphene sheets for photocatalysis applications

N.R. Khalid,E. Ahmed,Zhanglian Hong,Yuewei Zhang,M. Ahmad 한국물리학회 2012 Current Applied Physics Vol.12 No.6

Nitrogen doped TiO2 nanoparticles decorated on graphene sheets are successfully synthesized by a lowtemperature hydrothermal method. The resulting GR-N/TiO2 composites are characterized by X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-Ray photoelectron spectroscopy (XPS) and Transmission Electron Microscopy (TEM). The optical properties are studied using UVevisible diffuse reflectance spectroscopy (DRS), which confirms that the spectral responses of the composite catalysts are extended to the visible-light region and show a significant reduction in band gap energy from 3.18 to 2.64 eV. Photoluminescence emission spectra verify that GR-N/TiO2 composites possess better charge separation capability than pure TiO2. The photocatalytic activity is tested by degradation of methyl orange (MO) dye under visible light irradiation. The results demonstrate that GR-N/TiO2composites can effectively photodegrade MO, showing an impressive photocatalytic enhancement over pure TiO2. The dramatically enhanced activity of composite photocatalysts can be attributed to great adsorption of dyes, enhanced visible light absorption and efficient charge separation and transfer processes. This work may provide new insights into the design of novel composite photocatalysts system with efficient visible light activity.

Synthesis of geopolymer-supported zeolites via robust one-step method and their adsorption potential

Khalid, Hammad R.,Lee, N.K.,Park, S.M.,Abbas, N.,Lee, H.K. Elsevier 2018 Journal of hazardous materials Vol.353 No.-

<P><B>Abstract</B></P> <P>The present study proposes a robust one-step hydrothermal treatment method for synthesis of high strength geopolymer-supported zeolites utilizing industrial by-products (fly ash and blast furnace slag), which can be potentially used as bulk-type solid adsorbents. The results revealed that the geopolymer-supported zeolites, possessing distinct strengths, zeolite phases (Na-P1, Na-chabazite, and analcime) and pore features depending on the mix design and synthesis conditions, can be easily synthesized employing the proposed one-step method. The geopolymer-supported zeolites exhibited the characteristics of mesoporous materials which are typically desired for commercial adsorbents. The maximum adsorption capacity for Pb<SUP>2+</SUP> was found to be about 37.9 mg/g which is relatively higher than the other bulk-type adsorbents reported for Pb<SUP>2+</SUP> to date. Since industrial by-products are used for synthesis of these materials, it will help in reducing the environmental hazards associated with the permanent disposal of such by-products, with an added advantage that these bulk-type solid adsorbents can be easily retrieved after use unlike granular adsorbents.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A robust one-step method is proposed to synthesize geopolymer-supported zeolites. </LI> <LI> <I>Z</I>eolite yield was highly correlated with time, pressure, molarity and slag content. </LI> <LI> Synthesized samples exhibited the characteristics of mesoporous materials. </LI> <LI> A high adsorption capacity of 37.9 mg, Pb2+/g, bulk-type adsorbents was achieved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Novel Sn-doped WO3 photocatalyst to degrade the organic pollutants prepared by green synthesis approach

N. R. Khalid,Samavia Ilyas,Faisal Ali,Tahir Iqbal,M. Rafi que,Muhammad Imran,Mohammad A. Assiri 대한금속·재료학회 2024 ELECTRONIC MATERIALS LETTERS Vol.20 No.1

The organic pollutants are polluting the drinking water so, it is a fi eld of great interest to clean this water by using somesophisticated materials. For this purpose, the nanostructured materials are playing vital role to attain sustainable and puredrinking water by degrading organic pollutants. The synthesis of such photocatalytic material without using harmful chemicals,is one of the important existing challenges. Thus, to tackle this challenge, we have prepared green synthesized Sn-dopedWO 3 nanomaterials by varying the content of Sn from 2 to 6 wt% and assisting from moringa oleifera seeds’ extract. Thecrystal structure, morphology, optical and photoluminescence properties of as prepared samples were investigated throughx-ray diff raction (XRD), scanning electron microscopy (SEM), ultraviolet visible spectroscopy (UV-vis) and photoluminescencespectroscopy (PL) techniques. Among of as prepared samples, the 4Sn-WO 3 (4 wt% Sn doped WO 3 ) sample hasexhibited the reduced optical band gap value i.e. 2.80 eV than 3.02 eV for pure WO 3 sample. This optimized sample has alsoshown the lowest e-h recombination rate. To test the photocatalytic performance, the methylene blue was used as a modeldye. Out of all samples, 4Sn-WO 3 sample has shown 95% degradation activity against this water pollutant. These fi ndingsspecify that the as mentioned novel photocatalytic nanomaterial will provide a signifi cant advancement in the environmentalfi eld to degrade the organic pollutants.

Field Evaluation of Mungbean Recombinant Inbred Lines against Mungbean Yellow Mosaic Disease Using New Disease Scale in Thailand

Khalid P. Akhtar,R. Kitsanachandee,P. Srinives,G. Abbas,M. J. Asghar,T. M. Shah,B. M. Atta,O. Chatchawankanphanich,G. Sarwar,M. Ahmad,N. Sarwar 한국식물병리학회 2009 Plant Pathology Journal Vol.25 No.4

Studies were conducted to identify the sources of resistance in mungbean recombinant inbred lines (RILs) in Thailand against mungbean yellow mosaic disease (MYMD). 146 mungbean RILs in F8 series were evaluated in a field including resistant parent NM-10- 12-1 and susceptible parent KPS 2 during summer 2008 under high inoculum pressure. The RILs were subsequently scored for disease symptom severity ratings (DSSR) using a new scale. Observations regarding DSSR and % disease index (%DI) showed that the tested RILs responded differently to the disease. A large number of RILs (132) were found highly susceptible, 12 were susceptible, 3 were tolerant and one was resistant. Overall screening results showed that three RILs, viz. line no. 30, 100 and 101 had minimum DSSR and % disease index thus they are good source of resistance to MYMD in spite of high disease pressure and can therefore be used directly as varieties to manage the disease in Thailand.

Evolution of zeolite crystals in geopolymer-supported zeolites: effects of composition of starting materials

Khalid, Hammad R.,Lee, N.K.,Choudhry, Iqra,Wang, Zhen,Lee, H.K. Elsevier 2019 Materials letters Vol.239 No.-

<P><B>Abstract</B></P> <P>The role of the characteristics of raw materials and starting mix proportion on geopolymerization and evolution of zeolitic crystals from an amorphous geopolymeric gel was investigated. Different types and compositions of metakaolin, fly ash, and slag were activated using same waterglass and NaOH-based alkali activator. The test results showed that the reactivity of alkali-activated raw materials greatly depends on the Si/Al and Si/Na ratios of the starting mix, which affected the strength development and zeolite formation. It was further found that low-Ca class F fly ash was the most suitable to obtain zeolite Na-P1 crystals. Alternatively, high-Ca class C fly ash promoted the synthesis of hydroxysodalite and calcite. Higher porosity (52%) and surface area (99.5 m<SUP>2</SUP>/g) were achieved for the geopolymer-supported zeolites. These materials can be potentially used as membranes/filters for removal of hazardous contaminants (colloidal foulants, macromolecules, heavy metals/radionuclides) from water owing to their porous structure and affinity of zeolites towards cations.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effects of different starting materials on zeolite evolution in geopolymer binders. </LI> <LI> Compressive strength increased with Si/Al and Si/Na ratios of the starting mix. </LI> <LI> Low Ca fly ash promoted conversion of geopolymeric gel to zeolite Na-P1. </LI> <LI> High Ca fly ash/slag resulted in formation of hydroxysodalite and calcite. </LI> <LI> Synthesized materials have potential to be used as self-supported adsorbents. </LI> </UL> </P>

Field Evaluation of Mungbean Recombinant Inbred Lines against Mungbean Yellow Mosaic Disease Using New Disease Scale in Thailand

Akhtar, Khalid P.,Kitsanachandee, R.,Srinives, P.,Abbas, G.,Asghar, M.J.,Shah, T.M.,Atta, B.M.,Chatchawankanphanich, O.,Sarwar, G.,Ahmad, M.,Sarwar, N. The Korean Society of Plant Pathology 2009 Plant Pathology Journal Vol.25 No.4

Studies were conducted to identify the sources of resistance in mungbean recombinant inbred lines (RILs) in Thailand against mungbean yellow mosaic disease (MYMD). 146 mungbean RILs in $F_8$ series were evaluated in a field including resistant parent NM-10-12-1 and susceptible parent KPS 2 during summer 2008 under high inoculum pressure. The RILs were subsequently scored for disease symptom severity ratings (DSSR) using a new scale. Observations regarding DSSR and % disease index (%DI) showed that the tested RILs responded differently to the disease. A large number of RILs (132) were found highly susceptible, 12 were susceptible, 3 were tolerant and one was resistant. Overall screening results showed that three RILs, viz. line no. 30, 100 and 101 had minimum DSSR and % disease index thus they are good source of resistance to MYMD in spite of high disease pressure and can therefore be used directly as varieties to manage the disease in Thailand.

Adsorption characteristics of cesium onto mesoporous geopolymers containing nano-crystalline zeolites

Lee, N.K.,Khalid, Hammad R.,Lee, H.K. Elsevier 2017 Microporous and mesoporous materials Vol.242 No.-

<P><B>Abstract</B></P> <P>The present study investigates the adsorption of cesium onto high-strength bulk-type mesoporous geopolymers containing nano-crystalline zeolites. Fly ash/slag-based mesoporous geopolymers were synthesized by a hydrothermal treatment. Batch adsorption studies were carried out with different initial cesium concentrations, solution pH values, and contact time with adsorbent. Kinetic and isothermal studies were also conducted against the experimental results to comprehend the mechanism and equilibrium condition of adsorption process. A higher removal efficiency of 96% (against 100 mg/L initial concentration) was observed and the maximum adsorption capacity of the mesoporous geopolymers was found to be 15.24 mg/g. The results showed that these mesoporous geopolymer adsorbents have the potential to be used for the removal of hazardous contaminants from aqueous solutions as self-supporting sieves.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bulk-type geopolymers, containing zeolites, were synthesized from fly ash and slag. </LI> <LI> Mesoporous geopolymers showed excellent cesium removal efficiency (96%). </LI> <LI> The adsorption process of cesium includes physisorption as well as chemisorption. </LI> <LI> These can be used as high strength self-supporting geopolymer-zeolite sieves. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Synthesis of mesoporous geopolymers containing zeolite phases by a hydrothermal treatment

Lee, N.K.,Khalid, H.R.,Lee, H.K. Elsevier 2016 Microporous and mesoporous materials Vol.229 No.-

<P>The present study investigates the synthesis of mesoporous geopolymers containing different nano crystalline zeolite phases. A hydrothermal treatment procedure was utilized to synthesize the mesoporous geopolymers using fly ash, slag and alkaline solution. The effects of slag addition and molar ratio of alkaline solution on the microstructure and mechanical strength of the geopolymers were investigated and evidenced by XRD analysis, compressive strength and nitrogen adsorption tests. The test results showed that the geopolymers incorporating fly ash and slag consisted of Na-P1 and Sodalite zeolite phases, and had the characteristic of mesoporous materials (2 nm < pore size < 50 nm) in which capillary condensation may occur. The highest compressive strength of the geopolymers was 16.57 MPa, and the desired mesoporous characteristics were met by adding 20% slag content to fly ash and adopting the hydrothermal process at a relatively low temperature. The highest BET surface area and single point adsorption pore volume of the mesoporous geopolymers were 114.16 m(2)/g and 0.2677 cm(3)/g, respectively. (C) 2016 Elsevier Inc. All rights reserved.</P>

Preparation of highly efficient Al-doped ZnO photocatalyst by combustion synthesis

M. Ahmad,E. Ahmed,Yuewei Zhang,N.R. Khalid,Jianfeng Xu,M. Ullah,Zhanglian Hong 한국물리학회 2013 Current Applied Physics Vol.13 No.4

Novel Al-doped ZnO (AZO) photocatalysts with different Al concentrations (0.5e6.0 mol%) were prepared through a facile combustion method and followed by calcination at 500 ℃ for 3 h. The obtained nanopowders were characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM) combined with EDX, transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), UVevis spectroscopy and photoluminescence spectroscopy. The XRD patterns of AZO nanopowders were assigned to wurtzite structure of ZnO with the smallest crystallite size about 11 nm consistent with the results from TEM. The doping of Al in ZnO crystal structure successfully suppressed the growth of ZnO nanoparticles confirmed by XRD patterns. The absorption spectra analysis showed that the optical band gap energy (Eg) for the AZO nanopowders were in the range of 3.12-3.21 eV and decreased with increasing of Al dopant. The photocatalytic activities of the samples were evaluated by photocatalytic degradation of methyl orange under visible light (λ≥ 420 nm) and sunlight irradiation. The results showed that the AZO photocatalyst doped with 4.0 mol% Al exhibited five times enhanced photocatalytic activity compared to pure ZnO. The enhanced photocatalytic activity could be attributed to extended visible light absorption, inhibition of the electronehole pair’s recombination and enhanced adsorptivity of MO dye molecule on the surface of AZO nanopowders.