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Adsorption of Benzene from Aqueous Solution Using Base Modified Expanded Perlite
Appiah-Ntiamoah, Richard,Mai, Xuan Thang,Momade, Francis W.Y.,Kim, Hern Trans Tech Publications, Ltd. 2012 Advanced materials research Vol.622 No.-
<P>In this study, the adsorption capacity of expanded perlite (EP) for benzene at low concentrations in water was investigated after EP was treated with sodium hydroxide (NaOH). IR spectra used to characterize the modified EP showed that there was no bonding between NaOH and the hydroxyl groups on the surface of EP. However, the NaOH provided a basic medium for negatively charged surface oxide ions (-SO-) to form on EP. This fact was corroborated by pH readings of the modification solution. This reduced in pH from 10 to 9 at the end of the reaction which indicated that the hydroxyl OH- groups on the EP underwent deprotonation and hence releases H+ into the solution, and also positive sites on EP adsorbed OH- ions from the base solution. Mahir et al. in their paper Zeta potential of unexpanded and expanded perlite samples in various electrolyte media confirmed that EP has no isoelectric point and exhibits negative zeta potential in the pH range of 2-11. The surface oxides (-SO-) were believed to have given EP it adsorptive potential. Adsorption isotherm values correlated reasonably well with the Langmuir isotherm model and it parameters (qo and K) were obtained using linear regression analysis. A maximum adsorption capacity (qo) value of 19.42 mg/g was achieved.</P>
A highly selective <b>SBA-15</b> supported fluorescent “turn-on” sensor for the fluoride anion
Appiah-Ntiamoah, Richard,Chung, Wook-Jin,Kim, Hern The Royal Society of Chemistry 2015 NEW JOURNAL OF CHEMISTRY Vol.39 No.7
<P>In an effort to improve the performance of organic-based F<SUP>−</SUP> receptors, organo-silica receptors are being developed taking advantage of the large surface area that mesoporous silica offers. In this work, we investigated the possibility of using a simple “piece-wise” assembly method to immobilize silyl-ether protected fluorescein isothiocyanate (FITC) molecules (receptor <B>1</B>) on the surface of 3-aminopropyltrimethoxysilane (APTES) and 3-[2-(2-aminoethylamino)ethylamino] propyltrimethoxysilane (APAEAETMS) modified <B>SBA-15</B> to form sensors <B>ASBA</B> and <B>TSBA</B>, respectively. We showed that aqueous solutions of <B>TSBA</B> (or <B>ASBA</B>) produce distinct changes in absorption and emission spectra upon F<SUP>−</SUP> addition due to the F<SUP>−</SUP> directed cleavage of Si–O bonds on receptor 1. <B>TSBA</B> (or <B>ASBA</B>) remained stable upon prolonged exposure to UV light (losing ∼0.12% of its fluorescence intensity), and was highly selective towards F<SUP>−</SUP> over other common anions (Cl<SUP>−</SUP>, Br<SUP>−</SUP>, I<SUP>−</SUP>, HPO<SUB>4</SUB><SUP>2−</SUP>, ACO<SUP>−</SUP>, and NO<SUB>3</SUB><SUP>−</SUP>). Furthermore, the sensitivity of this type of sensor architecture followed a dependence on the kind of amino-silane compound used, which opens up the possibility of synthesizing sensors with tailored detection limits. The detection limit of <B>TSBA</B> and <B>ASBA</B> was 0.02 μM and 0.5 μM, respectively.</P> <P>Graphic Abstract</P><P><B>TSBA</B> (or <B>ASBA</B>) remained stable upon prolonged exposure to UV light (losing ∼0.12% of its fluorescence intensity), and was highly selective towards F<SUP>−</SUP> over other common anions (Cl<SUP>−</SUP>, Br<SUP>−</SUP>, I<SUP>−</SUP>, HPO<SUB>4</SUB><SUP>2−</SUP>, ACO<SUP>−</SUP>, and NO<SUB>3</SUB><SUP>−</SUP>). <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5nj00495k'> </P>
Richard Appiah Ntiamoah,김헌 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.2
Organo-electrochromic materials hold promising applications in the next generation of flexible displays and smart windows. Currently, viologen/poly-ionic liquid composites dominate research in this field. In this study we investigate fluorescein isothiocyanate/poly-ionic liquid composites (FITC-PIL) as a viologen-free alternative. To this end we evaluate the effect of (i) different silane protection groups and (ii) degree of protection on the electrochromic properties of FITC-PIL. Our results show that FITC-PIL displays multiple colour regimes depending on (i) and (ii). Additionally, it is stable after long cycles. The chromic mechanism most likely originates from ring-opening or/and deprotection reactions under applied potential. A model application of FITC-PIL for smart windows shows results comparable to its viologen counterpart.
Detection of fluoride anion in water with mesoporous silica supported fluorescence probe
( Richard Appiah-ntiamoah ),김헌 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
A fluorescein-dye derivative, fluorescein isothiocyanate (FITC), was ‘assembled’ on amino-silane modified SBA-15 and used as a fluorescent probe to detect fluoride ions in total aqueous media. The ‘assembly’ synthesis method was devoid of tedious purification steps associated with conventional sensors. Moreover, the sensor was highly selective, sensitive, and responsive towards fluoride ions in aqueous media: Its detection limit was 0.02 μM, the lowest value reported for sensors of this nature. Furthermore, we showed that different amino-silane compound could be used to manipulate the detection limit of the sensor.
( Richard Appiah-ntiamoah ),( Bekelcha Tesfaye ),김헌 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
A major problem with adsorption technology is the generation of adsorbent-pollutant secondary waste materials. Currently, adsorbent regeneration is the best way to deal with this problem. However, this approach is inefficient because it cannot be done indefinitely. Herein, we show how adsorbent-organic waste can serve as effective pseudo- MOFs to synthesize anode materials for oxygen evolution reaction. ZnO-ZnFe<sub>2</sub>O<sub>4</sub>@Congo red system was used as a typical example of a secondary waste system. After annealing under N<sub>2</sub>, Congo red converts into N-doped porous graphitic carbon which wraps around ZnOZnFe<sub>2</sub>O<sub>4</sub>. The resulting composite achieves 10 mAcm-2 at a mere 240mV and remains stable for a long time.
Effect of crystallinity on supercapacitance property of transition metal ferrites
( Richard Appiah-ntiamoah ),김헌,( Bekelcha Tesfaye Gadisa ) 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
Transition metal ferrites (MFe2O4, M= Co, Ni, Zn) have emerged as excellent electrode materials for supercapacitor application because of their ease of synthesis, stability, abundance and benign nature. The transformation of MFe2O4 surface into oxyhydroxides (MFe2O4@M(Fe)OOH) under anodic potential is crucial to achieve high capacitive performance. In this study, we investigate how the degree of crystallinity in MFe2O4 affects the ease of MFe2O4@M(Fe)OOH formation and capacitance of MFe2O4 . Thermal annealing conditions (i.e. time (Tt) and temperature (T)) were tuned to control the crystallinity in MFe2O4. This was monitored using XRD, SAED and HR-TEM analysis. These methods were also used to elucidate MFe2O4 transformation into MFe2O4@M(Fe)OOH under anodic potential. Our results show a direct correlation between crystallinity and supercapacitance performance. These findings could theoretically be applied to improve the supercapacitance of other metal-oxide based electrodes.