Mahabubur Chowdhury

Catalytic activities of ultra-small β-FeOOH nanorods in ozonation of 4-chlorophenol

We report the catalytic properties of ultra-small β-FeOOH nanorods in ozonation of 4-chlorophenol (4-CP). XRD, TEM, EDS, SAED, FTIR and BET were used to characterize the prepared material. Interaction between O3 and β-FeOOH was evident from the FTIR spectra. The removal efficiency of 4-CP was significantly enhanced in the presence of β-FeOOH compared to ozone alone. Removal efficiency of 99% and 67% was achieved after 40min in the presence of combined ozone and catalyst and ozone only, respectively. Increasing catalyst load increased COD removal efficiency. Maximum COD removal of 97% was achieved using a catalyst load of 0.1g/100mL of 4-CP solution. Initial 4-CP concentration was not found to be rate limiting below 2×10(-3)mol/L. The catalytic properties of the material during ozonation process were found to be pronounced at lower initial pH of 3.5. Two stage first order kinetics was applied to describe the kinetic behavior of the nanorods at low pH. The first stage of catalytic ozonation was attributed to the heterogeneous surface breakdown of O3 by β-FeOOH, while the second stage was attributed to homogeneous catalysis initiated by reductive dissolution of β-FeOOH at low pH.

Rapid and large-scale synthesis of Co3O4 octahedron particles with very high catalytic activity, good supercapacitance and unique magnetic properties

The scarcity of rapid and large scale synthesis of functional materials hinders the progress from the laboratory scale to commercial applications. In this study, we report a rapid and large scale synthesis of micron size (1.3 μm) Co3O4 octahedron particles enclosed by (111) facets. The octahedron particles were composed of ±25 nm rectangular/cube shaped particles as seen from the TEM images. We have characterized and evaluated the catalytic, supercapacitance and magnetic properties of the as prepared material. The Co3O4 octahedron particles were highly active in heterogeneous PMS activation reaction. Formation of Co–OH bonding due to water molecule dissociation on the (111) surface of the particles was evident from the ELNEFS analysis. The as prepared octahedron materials showed >4 times higher pseudocapacitance properties (182 F g−1) with good capacity retention ability (up to the 1000 cycles studied) compared to commercial microcrystalline Co3O4 powder (43 F g−1). The material showed interesting magnetic properties at low temperature. The coexistence of superparamagnetic single domain and linear/quadratic behaviours was observed at low temperature for the as prepared Co3O4 octahedron particles.

A novel β-FeOOH/NiO composite material as a potential catalyst for catalytic ozonation degradation of 4-chlorophenol

In this study we report on the organic linker mediated fabrication and catalytic activity of a novel β-FeOOH/NiO composite material for the first time. Four-chlorophenol (4-CP) was used as a target molecule to evaluate the catalytic activity of the composite material in ozonation reactions. Three different β-FeOOH loadings, labelled 2, 5 and 10% β-FeOOH/NiO composites were prepared. The 5% β-FeOOH/NiO composite material showed the highest activity in the composite structure. XRD, FTIR and TEM were used to characterise the composite structure. Evidence of a chemically bonded interface between β-FeOOH and NiO was apparent from the FTIR and TEM results. Adsorption of 4-CP on the catalyst surface was found to be negligible. First order reaction kinetics were used to describe the 4-CP degradation behaviour and the rate constants increased with increasing initial pH of the solution. No detectable amount of both Fe and Ni leaching into the solution was observed at a pH range of 10–2.3. After 20 min of the ozonation reaction, 85% of 4-CP was removed by the heterogeneous system as opposed to 47% by ozonation alone. The developed composite material exhibited good recyclability as the catalytic activity of the material could be recovered by calcination after use. A maximum of 66% of COD was removed just after 50 min of the catalytic ozonation reaction. The enhanced catalytic activity of the composite material was due to higher generation of OH˙ which was supported by photoluminescence (PL) experiments.

Charge transfer between biogenic jarosite derived Fe3 + and TiO2 enhances visible light photocatalytic activity of TiO2

In this work, we have shown that mining waste derived Fe3+ can be used to enhance the photocatalytic activity of TiO2. This will allow us to harness a waste product from the mines, and utilize it to enhance TiO2 photocatalytic waste water treatment efficiency. An organic linker mediated route was utilized to create a composite of TiO2 and biogenic jarosite. Evidence of FeOTi bonding in the TiO2/jarosite composite was apparent from the FTIR, EFTEM, EELS and ELNEFS analysis. The as prepared material showed enhanced photocatalytic activity compared to pristine TiO2, biogenic jarosite and mechanically mixed sample of jarosite and TiO2 under both simulated and natural solar irradiation. The prepared material can reduce the electrical energy consumption by 4 times compared to pristine P25 for degradation of organic pollutant in water. The material also showed good recyclability. Results obtained from sedimentation experiments showed that the larger sized jarosite material provided the surface to TiO2 nanoparticles, which increases the settling rate of the materials. This allowed simple and efficient recovery of the catalyst from the reaction system after completion of photocatalysis. Enhanced photocatalytic activity of the composite material was due to effective charge transfer between TiO2 and jarosite derived Fe3+ as was shown from the EELS and ELNEFS. Generation of OH was supported by photoluminesence (PL) experiments.

β-FeOOH/TiO2 Heterojunction for Visible Light-Driven Photocatalytic Inactivation of E. coli

In this work, we report on the photocatalytic properties of β-FeOOH/TiO2 heterojunc‐ tion material for the inactivation of Escherischia coli. XRD, HRTEM, EELS, ELNEFS were used to characterize the as-prepared material. A log reduction of the initial bacterial population was achieved after 45 min of irradiation in the presence of 0.1 mL of hydrogen peroxide. The enhanced photocatalytic activity was due to the effective charge transfer between Ti4+, Fe3+, and O2+ as shown from the EELS analysis of the heterojunction structure. The role of various reactive species formed due to the photocatalytic reaction was also investigated. Presence of •OH radicals in the bulk solution was the key factor in the photocatalytic inactivation of E. coli.