Ecofriendly Reduction of Methylene Blue with Polyurethane Catalyst

Abstract

A number of physical, chemical, and biological technologies have been developed to address the issue of synthetic dyes in wastewater. One of the important chemical methods involves reduction of these stringent pollutants into less hazardous products. In this study, a cross-linked polyurethane foam (CPUF) was prepared from toluene diisocyanate (TDI), tetraethylenepentamine (TEPA), and polycaprolactone diol (PCL; Mw: 1000 g/mole). To avoid harmful reducing agents, ecofriendly reduction of methylene blue (MB) was executed with CPUF as catalyst where ascorbic acid and fresh juice extracts were applied as reducing agents. The FTIR and SEM analysis confirmed the chemical composition and porous morphology of CPUF, respectively. The 100% reduction of MB was recorded in just 15 minutes with ascorbic acid and CPUF, while similar result was obtained in 37 minutes in blank experiment composed of only MB and ascorbic acid. Thus, catalytic role of CPUF in reduction process was proved. Fresh fruit extracts also participated in the reduction process, but rate of reaction was accelerated in the presence of CPUF. The reusability study of the catalyst supported its stability and efficiency. All the successful reduction processes followed 1st-order kinetics with highest apparent rate constant for ascorbic acid. Furthermore, phytotoxicity evaluation proved safe reduction of MB with 60% germination index. Hence, it can be concluded that catalytic role of CPUF has been established with safe and biodegradable reducing agents which can be extended to other redox processes.

Adsorptive removal of vitamin B6 and ciprofloxacin using polyurethane foam in pure and pharmaceutical preparations: Kinetic and equilibrium studies

“…In addition to a weak peaks related to NCO at 2,260 cm −1. 35 …”

Treatment of Automotive Paint Wastewater: Photocatalytic degradation of methylene blue using semi-conductive ZrO2

“…The amount of dye remaining without degradation in samples taken from a certain volume of dye solution containing ZrO2 at different time intervals was determined by UV-Vis spectrometry. For all experiments, the dye degradation percentage was calculated with Equation 1 [22,23]:…”

“…It has been reported that the optical energy band gap of zirconia as a direct band gap insulator varies between 3.0 and 5.7 eV, and the low band gap may be related to oxygen deficiency in wide band gap semiconductors [41]. Navio et al [22] reported an energy band gap of 3.65 eV for monoclinic ZrO2 powders prepared by adding an aqueous solution of zirconium oxychloride and ferric nitrate to pH=9-10 and drying the gel at 600ºC.These authors argue that the decrease in band gap energy as a result of the conditions used in the sol-gel technique can be attributed to a highly disordered structure. As a result of structural defects, some energy levels are introduced into the semiconductor band gap, allowing lower energy transitions, thus leading to a decrease in the band gap energy [42].…”

Flower-Based Green Synthesis of Metallic Nanoparticles: Applications beyond Fragrance

“…Methylene blue (MB), which is the member of the thiazine class of dyes, is another heterocyclic aromatic industrial pollutant [118]. The ingestion of MB in human body has been reported to restrict oxidase enzymes in the body, which may lead to grave disorders, i.e., toxicity of the central nervous system, gastrointestinal infections and decolorization of the brain parenchyma [119,120]. During the reduction of MB, NaBH 4 acts as a reducing agent, and NPs act as an absorbent [121].…”