Simultaneous elimination of Malachite Green, Rhodamine B and Cresol Red from aqueous sample with Sistan sand, optimized by Taguchi L16 and Plackett-Burman experiment design methods

(E)-1,2-Diphenylethene-based conjugated nanoporous polymers for a superior adsorptive removal of dyes from water

A series of (E)-1,2-diphenylethene-based conjugated nanoporous polymers having extraordinary thermal stabilities, high surface areas, and superior adsorptive removal of dyes from water have been developed.

Fabrication of a Smartphone-Based Spectrophotometer and Its Application in Monitoring Concentrations of Organic Dyes

In this study, an in-house constructed paper-based spectrophotometer is presented and demonstrated for detecting three organic dyes, namely, methylene blue, malachite green, and rhodamine B, and monitoring the efficiency of their removal from a wastewater sample with Sistan sand as a costless adsorbent. The compact design and light weight of this simple spectrophotometer delivered portability, with materials costing less than a dollar. Spectral analysis of the captured images was performed using free downloadable software from the Google Play store. The main experimental parameters affecting the efficiency of dye adsorption including pH, sorbent dosage, initial dye concentration, and contact time were investigated and optimized using the Taguchi design experimental method. Validation experiments were performed using a standard commercial bench-top spectrophotometer, and results were compared in terms of analytical performance, speed, and cost of analysis. The smartphone-based spectrometer was able to measure accurately, as confirmed using the commercial spectrometer, with enhanced sensitivity for methylene blue and rhodamine B. The combination of the high spectral accuracy of the paper-based spectrophotometer, together with sand as a readily accessible sorbent, enabled us to develop a powerful yet simple approach and tool for the removal and monitoring of dyes within wastewater samples, which is potentially available to everybody who owns a smartphone.

Amino-functionalized graphene oxide-supported networked Pd-Ag nanowires as highly efficient catalyst for reducing Cr(VI) in industrial effluent by formic acid

Cr(VI) pollution in wastewater has increasingly become a global environmental problem owing to its acute toxicity. Herein, we present the one-pot procedure for preparing the amino-functionalized (-NH₂) graphene oxide (GO-) supported networked Pd-Ag nanowires by co-reduction growth in polyol solution, which show the highly efficient catalytic performance with the excellent cycling stability for the catalytic Cr(VI) reduction by formic acid as an in-situ source of hydrogen at room temperature. The electron transfer from Ag and amino to Pd increases the electron density of Pd, which enhances the catalytic formic acid decomposition and subsequent the catalytic Cr(VI) reduction. The catalytic reduction rate constant of Pd₃Ag₁/GO-NH₂ is determined to be 0.0768 min^-1, which is much superior to the monometallic Pd/GO-NH₂ and Pd₃Ag₁/GO. This study provides a novel strategy to develop catalysts for the catalytic reduction of Cr(VI) to Cr(III) in the industrial effluent using formic acid as an in-situ source of hydrogen.

Simultaneous Removal of Heavy Metals from Wastewater Using Modified Sodium Montmorillonite Nanoclay

Sodium montmorillonite nanoclay particles were modified by 3-aminopropyltrimetoxysilane using a physical vapor deposition method and applied for the simultaneous removal of Cd, Zn, Pb and Ni heavy metals from wastewater samples. Experiments were performed in both batch and column systems. Several parameters that influence the removal efficiency, such as the pH, contact time, amount of adsorbent, interfering ions, flow rate of sample passage and eluent solvent, were evaluated and optimized. The results showed that the adsorption isotherms obeyed Langmuir isotherms for all heavy metals. Also, interfering ions did not influenced the removal efficiency. Finally, modified nanoclay successfully could remove all heavy metals from real wastewater samples to near completeness.

New MOF/COF Hybrid as a Robust Adsorbent for Simultaneous Removal of Auramine O and Rhodamine B Dyes

In this study, by hybridization of zinc-based metal-organic framework-5 (MOF-5) and melamine-terephthaldehyde-based intergrade two-dimensional π-conjugated covalent organic framework (COF), a novel MOF-5/COF (M5C) hybrid material was prepared and characterized by Fourier transform infrared, field emission scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis. MOF-5 has a well-defined cubic structure, and the proposed COF has an orderly and spherical nanosize shape. The prepared MOF-5/COF was applied as an effective adsorbent for rapid and high-efficient simultaneous removal of auramine O (AO) and rhodamine B (RB) cationic dyes via electrostatic, H-bonding, Lewis acid-base interactions, and π-π stacking from aqueous solution. The effect of experimental parameters such as pH, M5C mass, contact time, and AO and RB dyes concentration was investigated for removal efficiency and optimized. The M5C adsorbent showed an adsorption capacity of 17.95 and 16.18 mg/g for AO and RB dyes, respectively, at pH 9.5. The adsorption study of AO and RB dyes by M5C comprises both isotherm and kinetic studies. The equilibrium adsorption data followed by Langmuir isotherm and the adsorption kinetic process were found to be a pseudo-second-order model. The robustness adsorption efficiency of MOF/COF hybrids can be attributed to the formation of amide bonds between COF and MOFs, which improve the stability of the adsorbent.