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Awual M.R.,Japan Atomic Energy Agency | Hasan M.M.,Shaheed Ziaur Rahman Medical College | Khaleque M.A.,Independent University, Bangladesh | Sheikh M.C.,University of Toyama
Chemical Engineering Journal | Year: 2016

A sensitive and selective colorimetric method for simultaneous detection and removal of copper (Cu(II)) ion from contaminated water samples was developed based on the functional ligand embedded mesoporous conjugate materials. The synthesized material's characterization was also presented. The conjugate materials exhibited an obvious color change from colorless to dark yellow in the presence of Cu(II) ion according to the pH values. Also, the Cu(II) ion were detected and removed through naked-eye. The prepared material exhibited significant color change upon addition of Cu(II) ion even in the presence of other competing ions, and the limit of detection was calculated to be 0.15. μg/L. Excellent selectivity toward Cu(II) ion was observed due to a specific complex formation between Cu(II) ion and organic ligand of the conjugate materials. In Cu(II) adsorption operation, several affecting factors, including the solution pH, contact time, initial Cu(II) ion concentration, foreign ions and reuses were investigated. The results showed that the conjugate materials exhibited excellent adsorption capacity and adsorption equilibrium was reached rapidly. The adsorption results were well fitted with Langmuir adsorption isotherms and the maximum adsorption capacity by the materials for Cu(II) ion was 174.76. mg/g. We claimed from this study that Cu(II) could be successfully detected and removed by the adsorption method developed in the current work. The present work is obviously much simpler and greener than the conventional comprising multistep processes. The results demonstrated that Cu(II) ion loaded conjugate materials was effectively regenerated using HCl acid solution, and the regenerated materials was repeated to use many cycles without significant capacity loss, indicating the good stability of prepared conjugate materials. © 2015 Elsevier B.V.

Awual M.R.,Japan Atomic Energy Agency | Hasan M.M.,Shaheed Ziaur Rahman Medical College
Microporous and Mesoporous Materials | Year: 2014

Lead (Pb(II)) is a very toxic heavy metal that even at low concentration can affect living organisms. Therefore, designing effective materials with high selectivity and cost-effeciency is essential for the control capturing of toxic Pb(II) ions. This study developed a ligand based conjugate adsorbent for simultaneous Pb(II) detection and removal from water samples. The organic ligand of 4-dodecyl-6-((4-(hexyloxy)phenyl)diazenyl) benzene-1,3-diol (DPDB) was synthesized and DPDB was successfully immobilized onto mesoporous silica by a direct immobilization approach. The Pb(II) ion was detected by the charge transfer (π-π transition) transduction mechanism with sensitivity and selectivity. The experiment conditions were optimized based on contact time, solution acidity, initial Pb(II) concentration and pH value and diverse metal salt concentrations. The adsorbent was highly sensitive, and the limit of detection was 0.18 μg/L for Pb(II) ions. The Pb(II) sorption synthetic aqueous solution also underwent batch tests. However, the sorption capacity depended on the solutions pH, initial concentration and to some extent on the competing ions. The experimental data revealed that the maximum Pb(II) sorption was possible at pH 5.0. The presence of other cations and anions did not adversely affect the Pb(II) capturing by the adsorbent. The maximum sorption capacity was determined to be as high as 195.31 mg/g. The extraction of Pb(II) ions from the saturated adsorbent was possible with 0.20 M HCl. The regenerated adsorbent that remained maintained the high selectivity to Pb(II) ions and exhibited almost the same sorption capacity as that of the original adsorbent. However, the sorption efficiency slightly decreased after ten cycles. Therefore, the proposed adsorbent offered a cost-effective material and may be considered a viable alternative for effectively monitoring and removing toxic Pb(II) ions from water samples without the need for sophisticated instrument. © 2014 Elsevier Inc. All rights reserved.

Awual M.R.,Japan Atomic Energy Agency | Hasan M.M.,Shaheed Ziaur Rahman Medical College
Sensors and Actuators, B: Chemical | Year: 2015

The nitrogen donor ligand was functionalized with polarable mesoporous silica as composite adsorbent, by a cost-effective and environmentally friendly procedure, for highly selective copper (Cu(II)) ions detection and removal from water. The nitrogen donor ligand of N,N(octane-1,8-diylidene)di(2-hydroxy-3,5-dimethylaniline) was synthesized to be specific to Cu(II) ions. The composite adsorbent permitted fast and specific Cu(II) ions capturing via colorimetric naked-eye detection based on stable complexation [Cu(II)-ligand]n+ mechanism. The effect of pH value, interferential metal ions, initial Cu(II) concentration, and contact time on adsorption capability were investigated systematically. The adsorbent was selective toward Cu(II) as shown by a light yellow to green color change. This was characterized by UV-vis spectroscopy and the color change was observed for the visual detection of Cu(II) ions. The ions selectivity of the adsorbent toward Cu(II) was determined by changes in UV-vis reflectance spectra. However, the presence of competing ions showed no interference for the detection of Cu(II) ion by the composite adsorbent. The results demonstrated that the composite adsorbent exhibited excellent sorption performance for Cu(II) ions. The low detection limit and sorption capacity of the adsorbent were 0.10 μg/L and 200.80 mg/g, respectively. The adsorbed Cu(II) was eluted with suitable eluent and simultaneously regenerated into the initial form for next operation without significant deterioration in its nanostructure case cavities. The data also confirmed that the adsorbent is a cost-effective and environmentally friendly procedure for Cu(II) treatment. Therefore, the composite adsorbent can be considered as a potential adsorbent for Cu(II) ions monitoring and removal from wastewater. © 2014 Elsevier B.V. All rights reserved.

Awual M.R.,Japan Atomic Energy Agency | Hasan M.M.,Shaheed Ziaur Rahman Medical College | Khaleque M.A.,Independent University, Bangladesh
Sensors and Actuators, B: Chemical | Year: 2015

Selenium occurs naturally in the environment and is toxic at elevated concentrations, which has been a challenging issue for environmental scientists. This work was devoted to the detection and removal the selenium (Se(IV)) from aqueous solutions using organic ligand an immobilized conjugate adsorbent. The organic ligand of (3-(3-(methoxycarbonyl) benzylidene)hydrazinyl) benzoic acid was synthesized and indirectly immobilized onto the mesoporous silica. The adsorbent was applied to detect and remove Se(IV) in aqueous solutions at optimum conditions. This adsorbent exhibited high surface area-to-volume ratios and pores were uniform nanostructures. The adsorbent permitted rapid Se(IV) capturing detectable by naked eye observation. The limit of detection was 2.02 μg/L by the proposed method of the conjugate adsorbent. The Se(IV) capture system was optimized by varying the parameters of contact time, pH, initial concentration, competing ions and elution operations. The pH effect played an important role and the solution pH ranging from 0.5 to 7.0 was investigated. The data confirmed that acidic pH enhanced the Se(IV) sorption on the conjugate adsorbent resulting in an increased sorption efficiency percentage of Se(IV) to >98% at pH 1.50. The data were also fitted to the Langmuir isotherm, and the maximum sorption capacity was 93.56 mg/g. The introduction of diverse ions was individually added to solution, and these had no significant effect on the Se(IV) sorption by the adsorbent. The 0.20 M NaOH was used an eluent in the elution operation, and the adsorbent was used in many cycles without loss of cage cavities. Therefore, the conjugate adsorbent has shown favorable capturing ability in water samples, and this could be used as efficient adsorbents in potential practical applications for Se(IV) detection and removal from wastewater. © 2014 Elsevier B.V. All rights reserved.

Awual M.R.,Japan Atomic Energy Agency | Hasan M.M.,Shaheed Ziaur Rahman Medical College
Journal of Industrial and Engineering Chemistry | Year: 2015

A simple and sensitive method was applied for determination and extraction of trace level palladium(II) in wastewater by using functionalized mesoporous silica based fine-tuning mesoporous adsorbent. The adsorbent was stable and easy to detect, adsorb and recover Pd(II) ions by charge transfer (intense π-π transition) complexation mechanism. The optimum experimental conditions such as pH, contact time, initial concentration, selectivity and sensitivity, type and amount of eluent for elution and various ionic interferences on detection and sorption were systematically evaluated. The determined maximum sorption capacity was 191.35. mg/g. The proposed method was applied successfully for extraction of Pd(II) in environmental wastewater samples. © 2014 The Korean Society of Industrial and Engineering Chemistry.

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