Removal Of Basic Triphenylmethane Dyes (Brilliant Green,Ethyl Violet) From Simulated Wastewater By Magnetic Nanocomposites

Synthetic dyes are widely produced and consumed in China,which are extensively used as colouring agents for plastics,wool,textile,ceramic,leather,cosmetics,paper,glass,ink,pharmaceutical and food.However,a large amount of wastewater is produced in the process of producing and using synthetic dyes,which causes serious environmental pollution.Triphenylmethane dyes are the third largest category in organic dyes after azo and anthraquinone dyes that difficult to degradate in nature.They have been proved to have carcinogenic,toxic and mutagenic effects on mammals.It is of great significance to study the removal of pollutants from the dyes wastewater.The mesoporous Pd-Fe bimetallic and Mn-doped Fe magnetic nanoparticles immobilized on the reduced graphene oxide were used in the present study for the decolorization of triphenylmethane dyes in simulated wastewater.By using brilliant green and ethyl violet synthetic dyes in triphenylmethane dyes as the representative pollutants.Two kinds of magnetic nanocomposites were characterized by X-ray diffraction,X-ray photoelectron spectroscopy,Raman spectroscopy,high-resolution transmission electron microscopy,scanning electron microscopy,superconducting quantum interference device,N₂-sorption,small angle X-ray diffraction and energy dispersive spectroscopy.The decolorization process was modeled and optimized by artificial intelligence?AI?technologies?artificial neural networks,particle swarm optimization,genetic algorithm,random forest and radial basis function?.The Pd-Fe/rGO nanocomposites possessed a Brunauer–Emmett–Teller surface area of164.1519 m²/g,a single point adsorption total pore volume of 0.4783 cm²/g,a Barrett-Joyner-Halenda adsorption average pore width of 10.8575 nm,and a narrow pore size distribution with a center of 3.47 nm,therefore they belonged to mesoporous materials.According to response surface methodology?RSM?,batch experiments were carried out to investigate the effect of operational parameters?i.e.initial p H?4–6?,initial concentration?400-600 mg/L?,contact time?2–8 min?and temperature?25-35 ???on the decolorization of brilliant green synthetic dye in aqueous solution.The predictive ability was evaluated for RSM and AI models?ANN-PSO and ANN-GA?developed based on the batch experiments.The results indicate that the ANN-GA model has a better prediction performance than the other two models.The experimental equilibrium data of BG adsorption onto Pd-Fe/rGO were fitted to the Langmuir and the Freundlich isotherm equations by linear and nonlinear methods.It was seen that the R² value obtained was better from the linear fitting.The adsorption equilibrium follows Freundlich isotherm and the maximum adsorption capacity of Pd-Fe/rGO was 3333.33 mg/g.Three kinetics models including pseudo-first-order,pseudo-second-order and Elovich equations were also utilized to examine the brilliantgreen decolorization process.It was found that the pseudo-second order kinetic model?R²= 0.9989?could satisfactorily describe the removal kinetics data.In addition,thermodynamic studies reveal that the adsorption process was spontaneous.Mesoporous Mn-doped Fe magnetic nanoparticles modified reduced graphence oxide?Mn-doped Fe/rGO?was prepared through a one-step co-precipitation method,which was then used to eliminate ethyl violet synthetic dye in wastewater.The ethyl violet synthetic dye elimination by Mn-doped Fe/rGO was modeled and optimized by artificial intelligence?AI?models.Among these AI models,ANN-GA is considered as the best model for predicting the removal efficiency of ethyl violet by Mn-doped Fe/rGO.The importance of four factors in the removal dye process was evaluated by the random forest,gradient boosting regression tree,variance analysis and Garson method,which shows that dosage gives the maximum importance to Mn-doped Fe/rGO removal of ethyl violet.The experimental data were fitted to kinetics and adsorption isotherm models.The results indicated that the process of ethyl violet removal by Mn-doped Fe/rGO obeyed the pseudo-second-order kinetics model and Langmuir isotherm,and the maximum adsorption capacity was 1000.00 mg/g.In summary,these mesoporous magnetic nanocomposites have the advantages of large specific surface area,fast decolorization,high adsorption capacity for brilliant green and ethyl violet synthetic dyes,and optimization of the removal process with the AI technologies was successful.