Investigation of kinetics, isotherms, thermodynamics and photocatalytic regeneration of exfoliated graphitic carbon nitride/zeolite as dye adsorbent

Synthesis, photocatalytic activity for tetracycline degradation under visible light, and kinetic study of Ag/AgCl/ZIF-11 nanocomposite

For the first time, Ag/AgCl/zeolitic imidazolate framework-11 nanocomposite (Ag/AgCl/ZIF-11) as photocatalyst was synthesized and investigated on tetracycline (TC) degradation under visible light. ZIF-11 (Z), Ag/AgCl (A), and four composites (AZ0.1Vis, AZ0.1UV24, AZ0.2UV12, AZ0.2UV24) were made and characterized by XRD, FTIR, Raman, BET, SEM, EDS, XPS, and DRS analysis. The characteristic peaks of ZIF-11 and Ag were observed at 4.3 and 38.2° in the XRD pattern of AZ0.2UV24, respectively. A good distribution of Ag/AgCl on the surface of ZIF-11 was observed by FESEM of AZ0.2UV24. The improvement of visible light absorption ability and reduced e-/h+ recombination of AZ0.2UV24 were confirmed by DRS and PL, respectively. The photocatalytic degradation of TC was described using the zero-order kinetic model with a degradation efficiency of 95.4%. The stability and reusability of AZ0.2UV24 were investigated during three consecutive cycles. Finally, the results of this study provide convincing evidence for using Ag/AgCl/ZIF-11 as highly efficient photocatalysts for removing TC from aqueous solutions.

Application of cloud point extraction coupled with derivative spectrophotometry to remove binary mixture of Cresol Red and Methyl Orange dyes from aqueous solutions: Box-behnken design optimization

Cloud point extraction (CPE) was employed to eliminate Cresol Red (CR) and Methyl Orange (MO), as anionic dyes in a binary mixture from aqueous solutions. To remove these dyes Triton X-100 and NaCl at pH 5.7 were utilized. In this vein, wavelengths of 365 nm and 520 nm were respectively selected for CR and MO using the derivative spectrophotometer and first-order derivatives. According to based on the first-order derivative spectrophotometry, the recoveries rised from 94.3 to 99.5 % for CR and from 94.6 to 99.1 % for MO. In the following, the response surface methodology was administered to investigate the effect of surfactant concentration, temperature, and time on the dyes' elimination process. The quadratic mathematical model was obtained from the Box-Behnken design (BBD) matrix and developed to estimate the impact of each variable and its relationship with the elimination parameters. Later, coefficients of determination (R2) ≥0.97 were obtained using model equations and comparison between predicted and empirical values. Analysis of variance estimated the models' significance and anticipation while processing the study variables. Based on the results, the model of pseudo-first-order in kinetic modelling can best describe dyes adsorption among the studied models. The analyzed dyes adhere to the Langmuir model with correlation values of 0.86 for CR and 0.87 for MO. The monolayer capacity (Qmax) was determined as 0.77 mol/mol for CR and 26.41 mol/mol for MO.

Investigation on novel chitin and chitosan from dung beetle Heteronitis castelnaui (Harold, 1865) and its potential application for organic dyes removal from aqueous solution

Chitosan, a natural polysaccharide, has attracted considerable attention as an environmentally friendly and highly efficient adsorbent for dye removal. It is usually produced by deacetylation or partial deacetylation of chitin. However, conventional sources of chitin and chitosan are limited, prompting the need for alternative sources with improved adsorption capabilities. Herein, this study focuses on exploring a novel chitin and chitosan source derived from the dung beetle and evaluates its potential for organic dye removal from aqueous solutions. The research involves the extraction and characterization of chitin and chitosan from dung beetle Heteronitis castelnaui (Harold, 1865) using various analytical techniques, including SEM, FT-IR, TGA, XRD, NMR, deacetylation degree and elemental analysis. The chitosan obtained was used for the formation of hydrogels with sodium alginate via cross-linking with calcium chloride. And then the prepared hydrogels were evaluated for its adsorption capacity through batch adsorption experiments using methylene blue as a model pollutant. The adsorption capacity for methylene blue was 1294.3 mg/g at room temperature with solution pH = 12, MB concentration of 1800 mg/L. Furthermore, the kinetics of the adsorption process were analyzed using pseudo-first-order and pseudo-second-order models to understand the rate of adsorption. The maximum adsorption capacities were determined using Langmuir and Freundlich isotherm models. This study provides valuable insights for the development of sustainable dye adsorption technologies, specifically investigating a novel chitosan source derived from the dung beetle.

One-step hydrothermal synthesis of CeVO4/bentonite nanocomposite as a dual-functional photocatalytic adsorbent for the removal of methylene blue from aqueous solutions

Cerium vanadate/modified bentonite (CeVO4/mbt) nanocomposite with different composition percentages was synthesized through a simple one-step hydrothermal method at 180 ℃, and then its photocatalytic activity was evaluated by decolorizing methylene blue (MB) in an aqueous solution under light exposure. In order to increase the surface area as an important parameter in photocatalytic processes, bentonite was modified by ball mill method. The structural and optical properties of the synthesized composites were determined by XRD, FT-IR, DRS, FESEM, EDS, and BET measurements. XRD and EDS results confirmed the successful synthesis of pure CeVO4. FESEM images and EDS mapping showed a proper distribution of rice-like CeVO4 nanoparticles on bentonite. The removal efficiency of MB with only 0.1 g of CeVO4/mbt nanocomposite in 15 min was about 99%, which is significant compared to neat bentonite and pure CeVO4 with efficiency of 30% and 57%. The mentioned nanocomposite followed the first-order kinetics, had a reaction rate constant equal to 0.1483 min-1, and showed acceptable stability in five consecutive cycles.

Premise setting for sustainable developing adsorption in environmental remediation using graphitic carbon nitride@agar-derived porous carbon composite

In the adsorption process for wastewater treatment, the adsorbent plays an important role. A composite adsorptive material composed of graphitic carbon nitride and agar-derived porous carbon (CNPC) was fabricated from simple precursors (melamine, thiourea, and agar) and through a facile procedure with different melamine and thiourea ratios. Characterization of CNPC proved a successful formation of a porous structure consisting of mesopores and macropores, wherein CNPC holds distinctive electrochemical (lowered resistance and higher specific capacity) and photochemical properties (lowered bandgap to 2.33 eV) thanks to the combination of graphitic carbon nitride (CN) and agar-derived porous carbon (PC). Inheriting the immanent nature, CNPC was subjected to the adsorption of methylene blue (MB) dye in an aqueous solution. The highest adsorption capacity was 133 mg/g for CNPC-4 which was prepared using a melamine to thiourea ratio of 4:4 - equivalent to the removal rate of 53.2 % and following the pseudo-I-order reaction rate. The effect of pH points out that pH 7 and 9 were susceptible to maximum removal and pretreatment is not required while the optimal ratio of 7.5 mg of MB and 30 mg of material was also determined to yield the highest performance. Furthermore, the reusability of the material for three consecutive cycles was evaluated based on two methods pyrolysis at 200 °C and photocatalytic degradation by irradiation under visible light. In general, the photocatalytic regeneration pathway is more ample and efficient than pyrolysis in terms of energy efficiency (saving energy over 10 times) and adsorption capacity stability. As a whole, the construction of accessible regenerative and stable adsorbent could be a venturing step into the sustainable development spearhead for industries.

Reduced electron/hole recombination in Z-scheme nanostructure of zeolitic imidazolate framework-11/graphitic carbon nitride as photocatalyst under visible light

In this research, for the first time, the synthesis of nanostructure of zeolitic imidazolate framework-11/graphitic carbon nitride (ZIF-11/g-C3N4 X) with different weight of g-C3N4 (X: 0.01, 0.1, 0.3 g) is reported. Their performance was compared in photocatalytic degradation of MB under visible light. Synthetic samples were characterized by X-Ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectrometer (XPS), diffused reflectance spectroscopy (DRS), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscope (TEM), Brunauer-Emmett-Teller (BET), Electrochemical Impedance Spectroscopy (EIS) and Photoluminescence (PL) analysis. Based on the results, Z-scheme ZIF-11/g-C3N4 0.3 was selected as the best sample. FESEM and TEM images indicated that g-C3N4 sheets were complicated on the surface of ZIF-11 with rhombic dodecahedron (RHO) morphology. The surface area and band gap of ZIF-11/g-C3N4 0.3 was determined as 174.5 m2/g and 2.58 eV, respectively. The recombination of charge carriers in the ZIF-11/g-C3N4 0.3 nanostructure was reduced. Photocatalytic degradation efficiency of MB (5 ppm), pH = 7, visible irradiation (120 W-60 min) using 0.1 g of ZIF-11/g-C3N4 0.3 was achieved 72.7% with first-order kinetic model and acceptable stability in three consecutive cycles. Further, the total organic carbon (TOC) removal rate by ZIF-11/g-C3N4 0.3 after 5 h were 66.5%.