Synthesis and characterization of novel nanozero-valent iron based bimetallic nanoparticles immobilized on bentonite as a new nanocatalyst for methyl orange and congo red dyes reduction

چکیده مقاله

Background: Water pollution is a serious issue which is in result of the rapid development of industries. In the effluents generated from textile, paper, leather, plastics, pharmaceutical and cosmetic industries, there are colored contaminants which are often reported as toxic, hazardous and carcinogenic material. Azo-dyes are an important class of them. Due to its toxicity to many organisms and its suspicious to carcinogenic mutagenicity, MO and CR which are benzidine-based anionic azo-dyes are banned in many countries. However, they are still widely used in several industries. MO and CR are synthetic dyes with aromatic structures and difficulty to biodegrade. It is required, even in trace amount, to develop innovative and low-cost processes to remove these dye molecules. Recently, using of various nanocatalysts for dye removal was considered. Compared to other physicochemical and biological technologies, in this method, the efficiency is higher, there is a selectivity toward nontoxic products, relatively mild conditions are required, and the operation is easier. Various materials have been used for catalytic dye removal to develop effective and selective nanocatalysts. Methods: Bentonite clay have been used to synthesize bentonite-supported bimetallic Fe/Cu for simultaneous reduction of MO and CR dyes [1, 2]. The synergistic effect between bentonite and nZVI based bimetallic nanoparticles resulting high removal efficiencies. The chief objectives were (1) characterization of the newly synthesized Be@Fe/Cu by BET, TEM, SEM-EDX, XRD, FT-IR, and XRF, (2) modeling and optimization of the parameters that affect the reduction procedure, and (3) elucidation of the most probable reduction mechanism of MO and CR dyes, as well as investigation of the real sample dyes removal. Results: The results of characterization showed that the nZVI biimetallic was successfully synthesized and immobilized on bentonite. Central composite design (CCD) was used to model and optimized the reduction procedure. Both coefficients of determination (R2) and adjusted-R2 obtained from the analysis of variance (ANOVA) were above 0.9, ensuring a satisfactory adjustment of the model with experimental results. Under the defined optimum conditions, the kinetic models parameters were investigated and the results showed the pseudo-second order model has good agreement with the procedure. Finally, under the defined optimum condition, the proposed nanocatalyst was successfully applied for dyes reduction from industrial wastewaters. Conclusion: The bimetallic nanocatalyst with bentonite as support for MO and CR dyes reduction simultaneously from aqueous solution are reported. The results suggest that the bentonite could effectively lighten the aggregation of nZVI bimetallic nanoparticles and enhance their reactivity towards dyes.