Scientia Iranica
Volume:30 Issue: 6, Nov-Dec 2023

In this study, the elimination of methylene blue (MB) by adsorption on Black Titania (B-TiO2) in an aqueous solution in the dark room is investigated. Preparation of B-TiO2 was carried out via the reduction of white TiO2 by NaBH4 in a tube furnace under an inert gas atmosphere at 600°C. Characterization of the absorbent was carried out by XRD, N2 adsorption-desorption, SEM mapping, photoluminescence, EDX analysis, Zeta potential, DLS, and FT-IR. The maximum adsorption capacity of B-TiO2 was found to be 88.65 mg g−1. The rate-limiting step was the intra-particle diffusion stage. The maximum adsorption was observed under the conditions: 26 mg of the B-TiO2 at pH 6 and MB concentration of 10 mg L−1. It was demonstrated that B-TiO2 might be recycled six times with very good adsorption results while keeping its high removal efficiency.

1D coordination polymer (CP) of [CuI(μ1,3-NCS)(DAFO)]n (CP1) (DAFO =  4,5-Diazafluoren-9-one) has been synthesized through branched tube method in ethanol and compared with previously synthesized CP2. Although both CPs synthesis methods and parameters were different, both of them formed in a similar crystal system (orthorhombic) and space group (Pmn21). The optical properties and structure of CP1 were further investigated in detail by bandgap energy (Eg = 5.63 eV), UV-Vis and FT-IR spectra. The difference in the crystallography temperature (CP1 in 290 K and CP2 in 200 K) causes slight differences in the bond lengths and angles in the geometry center. 3D Hirshfeld surface and 2D fingerprint plots analyses offer the predominance contribution of H–C⋯H (18.9%) for CP1 and H–C⋯H (19.9%) for CP2. The most obvious distinguishes in the interactions in both CPs are C–N (8.4%) and (3.3%), Cu–S (4.8%) and (0.0%), Cu–N (3.3%), and (11.4%) for CP1 and CP2, respectively. Due to the determined asymmetric unit of the crystal structure of both CPs, there are some distinctions in the HS and 2DFP analysis of the CPs. Solvent-free decomposition of CP1 crystals at 750 ℃ led to the synthesis of CuO nanoparticles with particles size of ~12 nm.

A novel chelating adsorbent was successfully synthesized by cross-linking of 4, 4', 4"-s-triazine-1, 3, 5-triyltri-p-aminobenzoic acid as a linker with nanosheets of graphene oxide to provide a 3-dimensional framework. Therefore, the adsorption process Cd2+ and Pb2+ on the adsorbent was investigated by employing an ultrasonic bath. The optimum condition containing the small amount of adsorbent (10 mg) for both metals at pH=8 for Cd2+ and pH=5 for Pb2+, and a short time of two minutes caused gaining an absorption capacity at a high level. The presence of nitrogen-functionalized groups in the porous graphene oxide framework (GOF) contributed to the absorption of lead and cadmium ions. To define the kinetic process the kinetic models of pseudo-first-order and pseudo-second-order were used. The experimental adsorption datum was properly-suited to the kinetic model of the pseudo-second-order (R2=0.99). It indicated that adsorbing ions of heavy metals onto GOF happens through a chemical process and adsorption isotherms of Cd2+ and Pb2+ ions were in high-grade accordance with the Longmuir model. Eventually, because of the rapid adsorption kinetics, high capacity for removing, perfect stability, and being reusable, this GOF can be used as a remediation adsorbent with high-performing heavy metals removal from aqueous solutions.

In this research, Polyether block amide (PEBA) containing different loadings of α-Al2O3 particles was deposited on top of the polysulfone (PSf ) supports to form PEBA 1657‒α-Al2O3/PSf multilayer composite mixed matrix membranes (MCMMMs). Multilayer Composite structure was used to overcome the sedimentation of fillers in the polymer matrix. Moreover, alpha phase of the Al2O3 particles was applied to improve the distribution of these particles at higher loadings. SEM, XRD, and FTIR tests were applied to study morphology, crystalline structure, and chemical structure of the membranes, respectively. Gas permeation properties of the membranes were also measured using three different pure gases (CO2, CH4, and N2) at the pressure of 7 bar and temperature of 25 ºC. CO2 permeance and ideal selectivity of CO2/CH4, and CO2/N2 for the optimum MCMMM with 20 wt% loading of α-Al2O3 particles were 25% (117.5 Barrer), 81.5 % (32), and 86.5% (57) higher than that of multilayer composite neat membrane (MCNM), respectively. The molecular simulation results confirmed the results of the experimental studies and approved that the α-Al2O3 particles are right candidates for improving the PEBA performance for CO2 separation.

This study clarifies the important role of nanofibers produced from polyacrylonitrile after reinforcement with iron nanoparticles (γ-Fe2O3), to expand the applications of these fibers and to combine their ability to remove Nickel (II) from aqueous solutions with their ability to remove pollutants such as total suspended solids, total nitrogen, chemical oxygen demand, and cyanide as well as killing the bacteria in wastewater. The results of the absorption of Nickel (II) after treatment of the aqueous solution were obtained by an atomic absorption spectrometer type (AAs-7000) and a spectrometer type (Hach DR2800) after treating samples of wastewater obtained pollutant absorption results. The adsorption kinetic parameters results for Nickle (II) proved that the rates of increase in the maximum absorption capacity were 43.27 to 133.5 and from 74.63 to 178.571 mg/g when increasing the initial concentration (10-50 mg/L) for first and second order models. The pH, contact time, electrical conductivity, and initial concentration are good indicators of adsorption efficiency of Nickel (II), the high removal efficiency was 23.96 % at low initial concentration. Also, an increase the reduction rate and increased in TN: TP ratio were significant to increase the reduction rate of the total bacteria up 90 % at 8 hours.

This research numerically surveys the effects of several main parameters of an agitated anaerobic digester on mixing rate and power input. The numerical simulation is handled applying the finite volume method (FVM), and it is validated with the available experimental data. The results indicate that doubling the blade length enhances the mixing rate by 39.9% and makes the power input enhance 13.5 times; increasing the number of blades (from 4 to 6) improves the mixing rate by 12.5% and makes the power input grow 1.4 times, and decreasing the blade tilt angle from 45° to 30° causes the mixing rate to drop by 14% and decreases the power input 1.8 times. Furthermore, the observations show that the mixing rate and power input are adversely influenced by the wastewater concentration. At last, the most effective impeller design, among 144 cases investigated, is found out and suggested.