Papers by Sridhar Komarneni
SSRN Electronic Journal, 2022
Journal of Cleaner Production, 2020
Nanoscale zero-valent iron (nZVI) is highly useful to remediate contaminants such as arsenic but ... more Nanoscale zero-valent iron (nZVI) is highly useful to remediate contaminants such as arsenic but it is currently difficult to be widely applied because of the complicated and costly synthesis process of nZVI. In this work, a novel production method by simple grinding of microscale ZVI with calcium carbonate (CaCO 3) is proposed to enhance the reactivity of ZVI for the removal of As(III) from water. The mechanically activated ZVI/CaCO 3 by the above grinding process was characterized by XRD, SEM-EDS, XPS, etc. The modified ZVI/CaCO 3 by grinding shows excellent As(III) removal performance and good regeneration property. The mechanisms of co-grinding ZVI with CaCO 3 leading to the increased reactivity of ZVI and resulting in enhanced As(III) removal are deciphered. The process of grinding helps to strip the original passivation layer from the surface of micro ZVI while the CaCO 3 prevents the agglomeration of ZVI during the grinding process and protects the fresh ZVI from forming a passivation layer. During the process of arsenic removal, the CaCO 3 covering on the surface of ZVI is continuously removed into the solution to expose fresh surface of ZVI simultaneously. In addition, the presence of CaCO 3 facilitates the corrosion of ZVI and the formation of Fe(II) and H 2 O 2 to trigger more highly reactive intermediates by Fenton reaction to promote the oxidation of As(III) to As(V) and Fe(II) to Fe(III), which results in dramatically enhanced As(III) removal. The presently developed simple grinding method using costeffective CaCO 3 remarkably improved the reactivity of ZVI and thus, offers an alternative for using microscale ZVI to deal with environmental pollution of arsenic more effectively and economically.
Ceramics International, 2019
Abstract Herein, we present a high-performance NO2 sensor operating at room temperature based on ... more Abstract Herein, we present a high-performance NO2 sensor operating at room temperature based on ZnO nanorods functionalized by nonplasmonic Pd nanoparticles. Optoelectronic measurements revealed that the ZnO/Pd hybrids exhibited high photocurrent with ultrafast rise/decay rates under visible light with optimal wavelength (λ = 475 nm), which was related to the photoexcited nonplasmonic electron injection from Pd nanoparticles to ZnO nanorods. Characterization of the visible-light-activated gas sensing performance is pursued at ppb-level of NO2 resulting in high responses, fast response/recovery rate, low detection limit as well as full reversibility. The enhanced optoelectronic NO2 sensing performance of the ZnO/Pd hybrid was attributed to the photoexcited nonplasmonic electrons. Here, we designed and demonstrated a high-performance NO2 sensing material utilizing the photoexcited nonplasmonic electrons from transition metal nanoparticles. This concept can also be extended to other metal oxide/transition metal nanoparticle heterostructures for optoelectronic devices.
Ceramics International, 2018
A spinel-type Co-Mn oxide was designed and synthesized through a two-step oxidation-precipitation... more A spinel-type Co-Mn oxide was designed and synthesized through a two-step oxidation-precipitation method at modest temperatures. The Co-Mn oxide was applied as the catalyst in the presence of NaHSO 3 under visible light irradiation in order to establish the superiority of heterogeneous photo-chemical catalysis system. In the above system, the Co-Mn catalyst exhibited much better catalytic capability than that in either single photocatalysis or chemocatalysis system, implying that the Co-Mn catalyst could well combine photocatalysis and chemocatalysis to obtain the highest degradation efficiency of up to 94% within 40 min when using Orange II as the target pollutant. Recycling experiments results showed that the as-obtained catalyst has excellent stability and recyclability. Powder X-ray diffraction (XRD) analysis showed that the as-obtained Co-Mn catalyst had a cubic MnCo 2 O 4.5 spinel structure. Because of relatively low temperature (180 ℃) synthesis, the catalyst was formed with nanoparticles (25-65 nm) and high specific surface area as confirmed by SEM and BET analyses. XPS indicated the presence of both manganese and cobalt species that serve as reactive sites for the catalytic oxidation reactions. Rational degradation mechanisms responsible for superior catalytic activity and durability were proposed based on a series of experimental results. The active species such as Mn(III), holes and sulfate and hydroxyl radicals were proposed to be responsible for the outstanding degradation results.
Applied Clay Science, 2018
Mn ternary metal oxide (Mn-LDO) was synthesized by MnO 4 − intercalation into NiFe-LDH and calcin... more Mn ternary metal oxide (Mn-LDO) was synthesized by MnO 4 − intercalation into NiFe-LDH and calcination to improve photocatalytic efficiency. The conventional Ni-Fe binary metal oxide (C-LDO) prepared from Ni-Fe-LDH was also employed for comparison. Bisulfite was added to the above oxides in order to improve the photocatalytic degradation during the reaction. The as-synthesized samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), Brunauer, Emmett, and Teller (BET), UV-Vis diffuse reflectance spectroscopy and X-ray photoelectron spectra (XPS). Photocatalytic activities of these catalysts were evaluated for methylene blue (MB) degradation under the visible light with and without the assistance of NaHSO 3. The results indicated that Mn-LDO showed superior photocatalytic decomposition capability of MB than that of C-LDO. Moreover, Mn-LDO showed much higher photocatalytic degradation efficiency of MB in the presence of NaHSO 3 than only the single Mn-LDO degradation system. The stability and recyclability of the catalyst were also investigated.
Journal of Porous Materials, 2019
Porous Ni/Co-organic framework with honeycomb-like structure was directly grown on the carbon clo... more Porous Ni/Co-organic framework with honeycomb-like structure was directly grown on the carbon cloth (Ni/Co-MOF@CC) through a hydrothermal process. The Ni/Co-MOF@CC displayed a high specific surface area with an average pore size of 3.05 nm and excellent conductivity. The electrochemical performances of the porous Ni/Co-MOF@CC as the electrode of supercapacitors were evaluated using cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy measurements in 2 M KOH electrolyte. The Ni/Co-MOF@CC electrode exhibited a maximal specific capacity of 1180.5 mC cm−2 at 3 mA cm−2, good high-rate discharge ability (624.1 mC cm−2 at 60 mA cm−2), and long-term cycling life (97.6% capacity retention after 5000 cycles). Our experiments demonstrated the practical application of mixed-MOFs as supercapacitors for next-generation energy storage devices.
Journal of Alloys and Compounds, 2019
To improve the efficiency of traditional advanced oxidation processes (AOPs), a novel photo-assis... more To improve the efficiency of traditional advanced oxidation processes (AOPs), a novel photo-assisted heterogeneous Fenton-like process was proposed and verified by experiments. Under visible light, NaHSO 3 and transition metal composite oxide MnO 2 /NiO were tested together for degradation of orange II (OII). MnO 2 /NiO nanocomposites were prepared by a hydrothermal method using different nickel oxide to manganese oxide ratios and characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Ultraviolet-vis (UV-vis) diffuse reflectance spectroscopy (DRS) and scanning electron microscopy (SEM). The best MnO 2 /NiO nanocomposite (Ni:Mn=1:2) which was designated as Ni-Mn-3 showed the best OII removal efficiency of about 92.8% among the various MnO 2 /NiO nanocomposites of different Ni:Mn ratios. Moreover, the best catalyst, Ni-Mn-3 also showed good stability and recovery performance for degrading OII. The degradation ability of Ni-Mn-3 decreased no more than 10% after three times of repeated tests, which makes it more competitive in practical industrial applications than other heterogeneous Fenton-like catalysts.
Applied Clay Science, 2018
Composite Co-Mn-Fe oxide catalysts were prepared by thermal decomposition of layered double hydro... more Composite Co-Mn-Fe oxide catalysts were prepared by thermal decomposition of layered double hydroxide (LDH) or hydrotalcite-like precursors. A series of catalysts at different Mn/Fe ratios were obtained and characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) spectrometry, UV-vis diffuse reflectance spectroscopy and BET surface area analysis. The catalysts were tested for methylene blue (MB) dye decomposition under visible light illumination with and without the assistance of NaHSO 3. When visible light illumination was used on the catalyst in the presence of NaHSO 3 , the degradation efficiency was greatly enhanced. All the Mncontaining samples showed much higher capability to degrade MB than that of MnO 2 under the same conditions. The [0]CoMnFe-LDO sample which did not contain any Mn showed lower degrading ability than MnO 2. In addition to determining the role of Mn and the Mn/Fe ratio of the complex oxide catalysts on the decomposition of MB, the stability and reusability of these complex oxide catalysts were also tested and found to be good.
Materials Science in Semiconductor Processing, 2018
Two different nanoclay minerals were combined with nanophase anatase TiO 2 for the synthesis of c... more Two different nanoclay minerals were combined with nanophase anatase TiO 2 for the synthesis of clay-based nanocomposites for improved photocatalytic properties. A new Halloysite (Hal) + Sepiolite (S)-TiO 2 ternary nanocomposite was prepared using halloysite from Utah, USA and a recently discovered sepiolite from Greece. Three nanocomposites were synthesized with Hal-TiO 2 , S-TiO 2 and [Hal+S] to TiO 2. As a result, TiO 2 particles (anatase) were homogeneously deposited and dispersed on the clay surfaces. Phase composition, particle morphology and physical properties of these nanocomposites were characterized by XRD, ATR-FTIR, FE-SEM, DRS-UV-Vis and N 2-sorption/desorption isotherms at 77 K. The photocatalytic activity of the clay mineral-TiO 2 nanocomposites was examined in the decomposition of paracetamol and tetracycline antibiotics as well as dye Rhodamine-B. The nanocomposites exhibited higher photocatalytic activity under UV irradiation for the decomposition of the targeted pollutants than the benchmark in the field, i.e. TiO 2-P25 photocatalyst.
Applied Catalysis B: Environmental, 2018
Novel hydrothermal electrodeposition to fabricate mesoporous film of Ni 0.8 Fe 0.2 nanosheets for... more Novel hydrothermal electrodeposition to fabricate mesoporous film of Ni 0.8 Fe 0.2 nanosheets for high performance oxygen evolution reaction,
Chemical Engineering Journal, 2018
Traditional chemical activation methods to prepare porous carbons adsorbents consume large amount... more Traditional chemical activation methods to prepare porous carbons adsorbents consume large amounts of activating agents through physical mixing. Herein, we developed a new strategy to prepare microporous carbons with uniform ultramicropores (~0.57 nm) through ionic activation method by using potassium carboxylate as an activating agent, which was uniformly incorporated onto the surface of hydrothermally prepared hydrochar. The ultramicroporous carbon adsorbent developed by this new method showed high CO 2 uptakes of 5.87 and 3.82 mmol g-1 at and 25 °C, respectively. We demonstrated that small amounts of uniformly distributed potassium carboxylate contributed to the development of ultramicroporosity. This research paves the way for a new route to prepare ultramicroporous carbons as efficient CO 2 adsorbents by using significantly lower amounts of activating agents and hence the process may be not only cost-effective but also avoids negative impacts of traditional chemical activation.
Ceramics International, 2017
A series of novel TiO 2-BiOCl-ZnCr-Ex composites for use as photocatalysts were synthesized via a... more A series of novel TiO 2-BiOCl-ZnCr-Ex composites for use as photocatalysts were synthesized via a facile solvothermal process using an exfoliated ZnCr-LDH (ZnCr-Ex) and depositing BiOCl and TiO 2 sequentially on the surface of ZnCr-Ex. The composites were characterized by XRD, TEM, SEM-EDS and UV-vis diffuse reflectance spectroscopy. In these composites, the BiOCl nanosheets were deposited first on the surfaces of ZnCr-Ex and then the TiO 2 nanoparticles were dispersed on the surface of BiOCl-ZnCr-Ex material as were seen from SEM and TEM analyses. The photocatalytic degradation of Rhodamine B (RhB) indicated that the TiO 2-BiOCl-ZnCr-Ex composite showed much higher visible-light photocatalytic activity for degradation of RhB than TiO 2 alone, BiOCl alone or the BiOCl-ZnCr-Ex by itself. The possible mechanisms of photocatalytic activity were discussed. Moreover, the present composite photocatalysts exhibited satisfactory re-usability for at least three cycles. Because of the facile synthesis process, higher photocatalytic activity under visible light irradiation and satisfactory re-usability of these composites, they can be touted as potential catalysts for degradation of organic pollutants in wastewater treatment.
Applied Clay Science, 2016
Abstract Hydroxy-Al pillaring agent was prepared and used to modify montmorillonite (Mt), and the... more Abstract Hydroxy-Al pillaring agent was prepared and used to modify montmorillonite (Mt), and the effects of temperature, initial Al3 + concentration and contact time were investigated by using a batch technique. The results showed that the uptake of Al13 by Mt increased with increasing temperature, initial Al3 + concentration and contact time. The adsorption equilibrium was achieved in 12 h as determined by kinetics. The adsorption kinetics demonstrated that the adsorption of Al13 by Mt followed the pseudo-second-order kinetic model. The adsorption isotherms at the temperatures of 40, 60, 80 and 90 °C were determined and simulated using Langmuir, Freundlich and Redlich-Peterson models. The three kinds of isotherms could represent the experimental data well. The specific surface areas and pillar density increased while the total porous volumes slightly decreased with increasing Al3 + concentrations. The XRD result showed that adsorbed Al13 ions were located in the Mt interlayer spaces through monolayer adsorption. Thermodynamic analysis of adsorption process showed that the adsorption of Al13 by Mt was spontaneous, endothermic with increasing disorder during the adsorption process and mainly physical in nature.
Microporous and Mesoporous Materials, 2016
A series of mesoporous ZIF-8/silica composites were prepared by a one-step surfactant mediated me... more A series of mesoporous ZIF-8/silica composites were prepared by a one-step surfactant mediated method. The as-synthesized ZIF-8/silica composites were characterized by XRD, TEM, SEM, nitrogen adsorption/desorption and thermogravimetric (TG) analyses. Foam like disordered mesoporous structure and narrow mesopore size distribution were formed in the composites, resulting in a high mesopore volume as well as specific surface area which can be varied by adding different amounts of silica precursor.
Applied Clay Science, 2017
Methoxy-grafted kaolinite is an excellent organic-inorganic compound, which serves as a precursor... more Methoxy-grafted kaolinite is an excellent organic-inorganic compound, which serves as a precursor to prepare new organic or inorganic kaolinite hybrid materials. Direct intercalation of kaolinite with dimethyl sulfoxide (DMSO), N-methylformamide (NMF) and urea (U) was achieved. All of the above intercalated kaolinites could be grafted by methoxy groups by reacting with methanol. The pre-intercalated molecules of DMSO, NMF and U blocked the grafting action at first but facilitated it at a later stage. Here, the mechanism of the structural collapse of methoxy-grafted kaolinite was proposed. Spontaneous deintercalation of small molecules such as water, ethanol, isopropanol and others was observed. Water and methanol molecules played an important role in the grafting action and also affected the structure of methoxy-grafted kaolinite. The d (001) of methoxy-grafted kaolinite was found to be in the range of 0.99-1.11 nm in wet state but constant at 0.86 nm for dry state. 13 C CP/ MAS NMR analysis confirmed that inner-surface hydroxyls were replaced by methoxy groups from methanol as detected by a 13 C MASNMR resonance at 51 ppm assigned to methoxy groups. 13 C MASNMR spectra of intercalated kaolinites confirmed that the pre-intercalated molecules were not displaced completely even though it cannot be detected by XRD. The hygroscopicity of the pre-intercalated molecules was found to affect the structure of methoxy-grafted kaolinite.
Microporous and Mesoporous Materials, 2017
High-yield production of mesoporous nanoscrolls from kaolinite by ultrasonic assisted exfoliation... more High-yield production of mesoporous nanoscrolls from kaolinite by ultrasonic assisted exfoliation, Microporous and Mesoporous Materials (2017),
Journal of Porous Materials, 2016
Al pillared montmorillonites (Al-PILM) were synthesized by the reaction of Na ?-montmorillonite (... more Al pillared montmorillonites (Al-PILM) were synthesized by the reaction of Na ?-montmorillonite (Na ?-Mt) and hydroxy-Al cation after pre-intercalation with dodecylamine (DA) under different drying methods and calcination temperatures. The results showed that Al-PILM dried at room temperature was more crystalline and had larger c-axis spacing, d (001) , BET specific surface area (S BET) and microporous volume, compared to those by common air-blast drying or vacuum drying and the superiority in the above properties of the drying methods is as follows: air drying [ air-blast drying [ vacuum drying. This suggests that natural air drying at room temperature favored the formation of more ordered pillar formation. It was also found that the pre-intercalation of DA had important influence on the physicochemical properties of Al-PILM. When the amount of pre-intercalated DA was 1/2 CEC of Na ?-Mt, c-axis spacing, d (001) , S BET and microporous volume of Al-PILM were increased and larger than those prepared without pre-intercalation of DA and the former sample had a more regularly ordered pillar distribution due probably to the reduced pillar density in the montmorillonite interlayers. The DA pre-intercalated PILMs were stable at a larger range of temperatures. With the increase of calcination temperature, the interlayer spacing d (001) value decreased, and the S BET and microporous volume increased firstly and then decreased. During calcination, the pre-intercalated DA was removed and the hydroxyl-Al cation was converted into the rigid Al 2 O 3 pillars, which resulted in decreased pillar size between Mt layers followed by porosity improvement of Al-PILM.
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Papers by Sridhar Komarneni