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Moztahida, Mokrema,Nawaz, Mohsin,Kim, Jiho,Shahzad, Asif,Kim, Seonghun,Jang, Jiseon,Lee, Dae Sung Elsevier 2019 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.370 No.-
<P><B>Abstract</B></P> <P>A reduced-graphene-oxide-loaded magnetite (rGOF) composite was successfully synthesized by co-precipitation method for photocatalytic degradation of an odorous water contaminant 2-methylisoborneol (MIB). This heterogeneous Fenton-like catalyst degraded the recalcitrant MIB under both UV and solar light irradiations at neutral pH without the addition of other chemicals. Bare magnetite (Fe<SUB>3</SUB>O<SUB>4</SUB>) degraded only 22.5% of MIB because of rapid charge recombination. In comparison, the degradation efficiency increased to 99% for 10% (by weight) reduced graphene oxide (rGO) loading in magnetite. The addition of the rGO not only increased the adsorption capacity by increasing surface area but also increased the photodegradation efficiency synergistically by separating the electron–hole pairs, indicated by the photoluminescence spectra. The reduction in aggregation of Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles was explained by the increase in d-spacing and with FE-SEM images. The impedance and photocurrent data also proved the transfer of electron in presence of light in the hybrid composite. The rGOF composite presented excellent ferromagnetism, which made its recovery very easy. The recycled composite showed significantly high photocatalytic activity even after the fifth cycle with increased adsorption capacity of the recycled composite. Degradation mechanism and degradation pathway have been proposed and intermediates were identified.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A Fenton-like composite (rGOF) was synthesized by co-precipitation. </LI> <LI> rGOF degraded 2-methylisoborneol (MIB) under both UV and visible light. </LI> <LI> rGO loading in Fe<SUB>3</SUB>O<SUB>4</SUB> enhanced the photodegradation of MIB. </LI> <LI> A loading of 10 wt% rGO (rGOF-10) was optimum. </LI> <LI> rGOF composite showed great reusability up to five cycles. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Moztahida, Mokrema,Jang, Jiseon,Nawaz, Mohsin,Lim, Seong-Rin,Lee, Dae Sung Elsevier 2019 Science of the Total Environment Vol.667 No.-
<P><B>Abstract</B></P> <P>Carbamazepine (CBZ), an anticonvulsant drug, is one of the most recalcitrant pharmaceuticals detected in wastewater. For the photocatalytic degradation of CBZ, visible light assisted heterogeneous Fenton-like hybrid composites were synthesized via a co-precipitation method by anchoring magnetite (Fe<SUB>3</SUB>O<SUB>4</SUB>) with reduced graphene oxide (rGO). The rGO loading not only reduced the aggregation of Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles, but also increased the adsorption capacity of the hybrid composites. The mass ratio of rGO in the composites substantially affected CBZ photocatalytic degradation and a 10 wt% rGO loading (rGF10) provided nearly complete CBZ degradation within 3 h. Moreover, the addition of rGO reduced the charge recombination of the bare Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles and provided more accessible reactive sites, enhancing the degradation capacity. The visible light excited Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles yielded reactive species such as hydroxyl radicals (·OH), holes (h<SUP>+</SUP>), and superoxide radicals (O<SUB>2</SUB>·<SUP>−</SUP>) during the photodegradation process that were evaluated by using specific scavengers during the degradation experiment. The hybrid catalyst was effective under wide pH ranges (from 3 to 9) and showed faster degradation rates in the acidic condition. The composites were magnetically separable, easily regenerated, and exhibited considerably high photocatalytic activity up to five cycles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A Fenton-like composite was synthesized by co-precipitation method. </LI> <LI> The composite photochemically degraded CBZ molecule under solar light. </LI> <LI> Certain amount of rGO loading in magnetite increased the photodegradation capacity. </LI> <LI> A 10 wt% rGO loading was optimum to get highest degradation capacity. </LI> <LI> The composite was reusable and the TOC removal was high after the reaction. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Photodegradation of microcystin-LR using graphene-TiO<sub>2</sub>/sodium alginate aerogels
Nawaz, Mohsin,Moztahida, Mokrema,Kim, Jiho,Shahzad, Asif,Jang, Jiseon,Miran, Waheed,Lee, Dae Sung Elsevier 2018 Carbohydrate polymers Vol.199 No.-
<P><B>Abstract</B></P> <P>In this study, sustainable graphene oxide-TiO<SUB>2</SUB>/sodium alginate and reduced graphene oxide-TiO<SUB>2</SUB>/sodium alginate aerogels were synthesized and the potential of these aerogels was investigated for microcystin-LR degradation in aqueous solution. Along with the role of alginate in the synthesis of aerogels, effects of different concentrations of photocatalyst, photolysis, pH, and combination of TiO<SUB>2</SUB> (anatase)/Degussa P25 with graphene were investigated in lieu of microcystin-LR photodegradation.The complete degradation of microcystin-LR was attained in case of reduced graphene oxide-TiO<SUB>2</SUB>/sodium alginate aerogel—not in graphene oxide-TiO<SUB>2</SUB>/sodium alginate aerogel case—by the synergistic effect of adsorption and photodegradation. The recyclability study of reduced graphene oxide-TiO<SUB>2</SUB>/sodium alginate aerogel demonstrated high stability and photoactivity and the degradation efficiency was not much hampered during six consecutive cycles of degradation reaction. The possible fragmentation pathways were also proposed based on identified intermediate products. High adsorption and degradation synergy and ease of separation/recycling of reduced graphene oxide-TiO<SUB>2</SUB>/sodium alginate aerogel can make it a suitable option for removing microcystin-LR from water systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Sodium alginate helped to synthesize a robust graphene-TiO<SUB>2</SUB> aerogel. </LI> <LI> Graphene-TiO<SUB>2</SUB>/sodium alginate aerogel efficiently degraded microcystin-LR. </LI> <LI> Synthesized aerogel was highly recyclable without producing any secondary pollution. </LI> <LI> In microcystin-LR degradation pathway, significant role of OH radicals was found. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Shahzad, Asif,Nawaz, Mohsin,Moztahida, Mokrema,Jang, Jiseon,Tahir, Khurram,Kim, Jiho,Lim, Youngsu,Vassiliadis, Vassilios S.,Woo, Seung Han,Lee, Dae Sung Elsevier 2019 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.368 No.-
<P><B>Abstract</B></P> <P>Two-dimensional (2-D) titanium carbide MXene core (Ti<SUB>3</SUB>C<SUB>2</SUB>T<SUB>x</SUB>) shell aerogel spheres (MX-SA) for mercuric ion removal were designed and fabricated with varying concentrations of Ti<SUB>3</SUB>C<SUB>2</SUB>T<SUB>x</SUB> MXene and sodium alginate (SA) using a facile method. Owing to their unique inside structures, high porosities, large specific surface areas, oxygenated functional groups of MXene nanosheets, and available active binding sites, the synthesized microspheres constitute a unique adsorbent for heavy metals removal in water. The MX-SA<SUB>4:20</SUB> spheres exhibit an exceptional adsorption capacity of 932.84 mg/g for Hg<SUP>2+</SUP>, which is among the highest value reported for adsorbents. The adsorbent exhibits high single- and multi-component removal efficiencies, with 100% efficiency for Hg<SUP>2+</SUP> and >90% efficiency for five heavy metal ions. The synthesized materials are highly efficient for Hg<SUP>2+</SUP> removal under extreme pH conditions (0.5–1.0 M HNO<SUB>3</SUB>) and have additional excellent reproducible properties. The micro-size and spherical shape of MX-SA<SUB>4:20</SUB> also allow it to be used in column-packed devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ti<SUB>3</SUB>C<SUB>2</SUB>T<SUB>x</SUB> nanosheets were synthesized using a low-toxicity etching agent (NH<SUB>4</SUB>F). </LI> <LI> Core-shell of MX-SA<SUB>4:20</SUB> spheres was capable of very effectively removing heavy metals. </LI> <LI> MX-SA<SUB>4:20</SUB> spheres exhibited exceptional Hg<SUP>2+</SUP> adsorption capacity of 932.84 mg g<SUP>−1</SUP>. </LI> <LI> MX-SA<SUB>4:20</SUB> performed excellently in extreme acidic conditions. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Fabrication of MX-SA<SUB>4:20</SUB> spheres through MXene-Alginate networking and their application in Hg<SUP>2+</SUP> uptake.</P> <P>[DISPLAY OMISSION]</P>
Tahir, Khurram,Miran, Waheed,Nawaz, Mohsin,Jang, Jiseon,Shahzad, Asif,Moztahida, Mokrema,Kim, Bolam,Azam, Mudassar,Jeong, Sang Eun,Jeon, Che Ok,Lim, Seong-Rin,Lee, Dae Sung Elsevier BV 2019 Science of the Total Environment Vol.688 No.-
<P><B>Abstract</B></P> <P>Anode potential is a critical factor in the biodegradation of organics in bioelectrochemical systems (BESs), but research on these systems with complex recalcitrant co-substrates at set anode potentials is scarce. In this study, carbamazepine (CBZ) biodegradation in a BES was examined over a wide range of set anode potentials (−200 to +600 mV vs Ag/AgCl). Current generation and current densities were improved with the increase in positive anode potentials. However, at a negative potential (−200 mV), current generation was higher as compared to that for +000 and +200 mV. The highest CBZ degradation (84%) and TOC removal efficiency (70%) were achieved at +400 mV. At +600 mV, a decrease in CBZ degradation was observed, which can be attributed to a low number of active bacteria and a poor ability to adapt to high voltage. This study signified that BESs operated at optimum anode potentials could be used for enhancing the biodegradation of complex and recalcitrant contaminants in the environment.</P> <P><B>Highlights</B></P> <P> <UL> <LI> LSV analysis showed anode potential enhanced the microbial colonization in BES. </LI> <LI> High potential favored BES, but after +400 mV, BES performance declined. </LI> <LI> CBZ biodegradation and TOC removal were enhanced in BES aided by anodic potential. </LI> <LI> Microbes with high tendency to degrade CBZ were enriched by a controlled potential. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>