Magnetic clay\zeolitic imidazole framework nanocomposite (ZIF-8@Fe3O4@BNT) for reactive orange 16 removal from liquid media

Decolorization of methylene blue by silver/reduced graphene oxide-ethylene diamine nanomaterial: synthesis, characterization, and optimization

In this study, ethylene diamine-coated reduced graphene oxide-supported silver composite (Ag/rGO-ED) was synthesized and used as an efficient catalyst for the decolorization of methylene blue (MB) in the presence of NaBH4. The morphology of the obtained material was elucidated using field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), and X-ray diffraction (XRD) techniques. The influences of four parameters (MB concentration (mg/L), NaBH4 amount (mM), catalyst amount (g/L), and contact time (s)) on the decolorization process were appraised and optimized via response surface methodology (RSM). For the decolorization of MB, the optimum solutions were obtained as Co of 32.49 mg/L, NaBH4 amount of 152.89 mM, catalyst amount of 0.83 g/L, and 101.39 s contact time with MB decolorization efficiency of 97.73%. MB, a pollutant in wastewater, was decolorized rapidly by Ag/rGO-ED with an efficiency of approximately 97%. The exploration of kinetics and thermodynamics was another major emphasis of the work. The activation energy (Ea) and rate constant (k) for the decolorization of MB were obtained as 37.9 kJ/mol and 0.0135 s-1, respectively. The obtained results show that the catalyst, a new composite material in the literature, is promising for decolorization of wastewater.

An eco-friendly chitosan-genipin/SiO2 composite for reactive orange 16 dye removal: Insights into adsorption statistical modeling and mechanism

The present work develops an effective bioadsorbent of cross-linked chitosan-genipin/SiO2 adsorbent (CHI-GNP/SiO2). The developed CHI-GNP/SiO2 was employed for the removal of organic dye (reactive orange 16, RO16) from simulated wastewater. The optimization of the fundamental adsorption variables (CHI-GNP/SiO2 dose, time, and pH) via the Box-Behnken design (BBD) was attained for achieving maximal adsorption capacity and high removal efficiency. The good agreement between the Freundlich isotherms and empirical data of RO16 adsorption by CHI-GNP/SiO2 indicates that the adsorption process follows a multilayer adsorption mechanism. The reasonable agreement between the pseudo-second-order model and the kinetic data of RO16 adsorption by CHI-GNP/SiO2 was obtained. The maximum RO16 adsorption capacity (qmax) of CHI-GNP/SiO2 was identified to be 57.1 mg/g. The adsorption capacity of CHI-GNP/SiO2 is attributed to its unique surface properties, including its highly porous structure and the presence of functional groups such as amino and hydroxyl groups. According to the results of this investigation, CHI-GNP/SiO2 has the potential to be an adsorbent for the removal of acidic dyes from wastewater.

Dual-functional marine algal carbon-based materials with highly efficient dye removal and disinfection control

The design and simple, green preparation of dual-functional materials for the decontamination of both hazardous dyes and pathogenic microorganisms from wastewater remain challenging currently. Herein, a promising marine algal carbon-based material (named C-SA/SP) with both highly efficient dye adsorptive and antibacterial properties was fabricated based on the incorporation of sodium alginate and a low dose of silver phosphate via a facile and eco-friendly approach. The structure, removal of malachite green (MG) and congo red (CR), and their antibacterial performance were studied, and the adsorption mechanism was further interpreted by the statistical physics models, besides the classic models. The results show that the maximum simulated adsorption capacity for MG reached 2798.27 mg/g, and its minimal inhibit concentration for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was 0.4 mg/mL and 0.2 mg/mL, respectively. The mechanistic study suggests that silver phosphate exerted the effects of catalytic carbon formation and pore formation, while reducing the electronegativity of the material as well, thus improving its dye adsorptive performance. Moreover, the MG adsorption onto C-SA/SP showed vertical orientation and a multi-molecular way, and its adsorption sites were involved in the adsorption process with the increase of temperature. Overall, the study indicates that the as-made dual-functional materials have good applied prospects for water remediation.

Rapid, Highly-Efficient and Selective Removal of Anionic and Cationic Dyes from Wastewater Using Hollow Polyelectrolyte Microcapsules

Herein, poly (allylamine hydrochloride) (PAH)/ poly (styrene sulfonic acid) sodium salt (PSS) microcapsules of (PAH/PSS)2PAH (P2P MCs) and (PAH/PSS)2 (P2 MCs) were obtained by a layer-by-layer method. The P2 MCs show high adsorption capacity for Rhodamine B (642.26 mg/g) and methylene blue (909.25 mg/g), with an extremely low equilibrium adsorption time (~20 min). The P2P MCs exhibited high adsorption capacities of reactive orange K-G (ROKG) and direct yellow 5G (DY5G) which were 404.79 and 451.56 mg/g. Adsorption processes of all dyes onto microcapsules were best described by the Langmuir isotherm model and a pseudo-second-order kinetic model. In addition, the P2P MCs loaded with reactive dyes (P2P–ROKG), could further adsorb rhodamine B (RhB) dye, and P2 MCs that had adsorbed cationic MB dyes could also be used for secondary adsorption treatment of direct dye waste-water, respectively. The present work confirmed that P2P and P2 MCs were expected to become an excellent adsorbent in the water treatment industry.

ZIF-8 metal organic framework materials as a superb platform for the removal and photocatalytic degradation of organic pollutants: a review

Metal organic frameworks (MOFs) are attracting significant attention for applications including adsorption, chemical sensing, gas separation, photocatalysis, electrocatalysis and catalysis. In particular, zeolitic imidazolate framework 8 (ZIF-8), which is composed of zinc ions and imidazolate ligands, have been applied in different areas of catalysis due to its outstanding structural and textural properties. It possesses a highly porous structure and chemical and thermal stability under varying reaction conditions. When used alone in the reaction medium, the ZIF-8 particles tend to agglomerate, which inhibits their removal efficiency and selectivity. This results in their mediocre reusability and separation from aqueous conditions. Thus, to overcome these drawbacks, several well-designed ZIF-8 structures have emerged by forming composites and heterostructures and doping. This review focuses on the recent advances on the use of ZIF-8 structures (doping, composites, heterostructures, etc.) in the removal and photodegradation of persistent organic pollutants. We focus on the adsorption and photocatalysis of three main organic pollutants (methylene blue, rhodamine B, and malachite green). Finally, the key challenges, prospects and future directions are outlined to give insights into game-changing breakthroughs in this area.

Decolorization of Rhodamine B by silver nanoparticle-loaded magnetic sporopollenin: characterization and process optimization

Silver nanoparticles (Ag NPs) were reduced on the surface of magnetic sporopollenin (Fe₃O₄@SP) modified with poly-dopamine to enhance the degradation capability for Rhodamine B (RhB). The polydopamine-coated Fe₃O₄@SP (PDA@ Fe₃O₄@SP) acts as a self-reducing agent for Ag⁺ ions to Ag⁰. The structural properties of the synthesized nanocomposite were determined using Fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS), and vibrating sample magnetometer (VSM). The systematic study of the degradation process was performed using Response Surface Methodology (RSM) to determine the relationship between the four process variables, namely, initial RhB concentration, NaBH₄ amount, catalyst amount, and time. Optimum points were determined for these four parameters using both matrix and numerical optimization methods. Under optimum conditions, RhB was decolorized with a yield of 98.11%. The apparent activation energy (E_a) and rate constant (k) for the degradation were 24.13 kJ/mol and 0.77 min^-1, respectively. The reusability studies of the Ag@PDA@Fe₃O₄@SP exhibited more than 85% degradation ability of the dye even after five cycles. As a result, Ag@PDA@Fe₃O₄@SP possessed high catalytic activity, fast reduction rate, good reusability, easy separation, and simple preparation, endowing this catalyst to be used as a promising catalyst for the decolorization of dyes in aqueous solutions.

Low-cost treated lignocellulosic biomass waste supported with FeCl3/Zn(NO3)2 for water decolorization

Dye pollution has always been a serious concern globally, threatening the lives of humans and the ecosystem. In the current study, treated lignocellulosic biomass waste supported with FeCl₃/Zn(NO₃)₂ was utilized as an effective composite for removing Reactive Orange 16 (RO16). SEM/EDAX, FTIR, and XRD analyses exhibited that the prepared material was successfully synthesized. The removal efficiency of 99.1% was found at an equilibrium time of 110 min and dye concentration of 5 mg L^-1 Adsorbent mass of 30 mg resulted in the maximum dye elimination, and the efficiency of the process decreased by increasing the temperature from 25 to 40 °C. The effect of pH revealed that optimum pH was occurred at acidic media, having the maximum dye removal of greater than 90%. The kinetic and isotherm models revealed that RO16 elimination followed pseudo-second-order (R² = 0.9982) and Freundlich (R² = 0.9758) assumptions. Surprisingly, the performance of modified sawdust was 15.5 times better than the raw sawdust for the dye removal. In conclusion, lignocellulosic sawdust-Fe/Zn composite is promising for dye removal.