Amine-rich quartz nanoparticles for Cu(II) chelation and their application as an efficient catalyst for oxidative degradation of Rhodamine B dye

Effective removal of As5+ from aqueous medium using date palm fiber biochar/chitosan/glutamine nanocomposite: kinetic and thermodynamic studies

In the current work, three adsorbent materials were developed: biochar derived from date palm fiber (C), date palm fiber biochar/chitosan nanoparticles (CCS), and biochar/chitosan nanoparticle composite supplemented with glutamine (CCSG). These compounds were used as solid adsorbents to remove As5+ from polluted water. Several characterization approaches were used to investigate all the synthesized solid adsorbents, including thermogravimetric analysis, N2 adsorption/desorption isotherm, scanning electron microscopy, transmission electron microscopy (TEM), attenuated total reflectance with Fourier transform infrared, and zeta potential. Date palm fiber biochar/chitosan/glutamine nanocomposite (CCSG) demonstrated good thermal stability, with a maximum specific surface area of 518.69 m2/g, a mesoporous size of 2.06 nm, total pore volume of 0.25 cm3/g, TEM average particle size of 38 nm, and pHPZC of 6.9. Contact time (5-60 min), pH (1-9), starting As5+ concentration (50-500 mg/L), adsorbent dose (0.1-2.0 g/L), temperature (27-45 °C), and ionic strength (0.05-0.40 mol/L) were among the sorption parameters that were investigated in order to improve the adsorption conditions. It is observed that the modified samples were effectively able to remove As5+ (CCS; 256.0 and CCSG; 376.0 mg/g) than unmodified ones (C; 150.5 mg/g). The As5+ removal procedure corresponded well with Langmuir isotherm model. Thermodynamic and kinetic experiments show that the Elovich, pseudo-first order, and Van't Hoff plot with endothermic, spontaneous, and physisorption nature are the best fitted models. EDTA has the highest desorption efficiency percentage (98.8%). CCSG demonstrated enhanced reusability after six application cycles of As5+ adsorption/desorption, with only a 4% decrease in the efficiency of adsorption. This work shows that adding glutamine to the DPF biochar/chitosan composite reinforces it, resulting in the fabrication of a solid adsorbent that shows promise for use in water remediation.

Copper supported Dowex50WX8 resin utilized for the elimination of ammonia and its sustainable application for the degradation of dyes in wastewater

To obtain high efficient elimination of ammonia (NH4+) from wastewater, Cu(II), Ni(II), and Co(II)) were loaded on Dowex-50WX8 resin (D-H) and studied their removal efficiency towards NH4+ from aqueous solutions. The adsorption capacity of Cu(II)-loaded on D-H (D-Cu2+) towards NH4+ (qe = 95.58 mg/g) was the highest one compared with that of D-Ni2+ (qe = 57.29 mg/g) and D-Co2+ (qe = 43.43 mg/g). Detailed studies focused on the removal of NH4+ utilizing D-Cu2+ were accomplished under various experimental conditions. The pseudo-second-order kinetic model fitted well the adsorption data of NH4+ on D-Cu2+. The non-linear Langmuir model was the best model for the adsorption process, producing a maximum equilibrium adsorption capacity (qmax = 280.9 mg/g) at pH = 8.4, and 303 K in less than 20 min. The adsorption of NH4+ onto D-Cu2+ was an exothermic and spontaneous process. In a sustainable step, the resulting D-Cu(II)-ammine composite from the NH4+ adsorption process displayed excellent catalytic activity for the degradation of aniline blue (AB) and methyl violet 2B (MV 2B) dyes utilizing H2O2 as an eco-friendly oxidant.

Peroxydisulfate-based Non-radical Oxidation of Rhodamine B by Fe-Mn Doped Granular Activated Carbon: Kinetics and Mechanism Study

While numerous persulfate-based advanced oxidation processes (AOPs) have been studied based on fancy catalysts, the practical combination of Fe or Mn modified granular activated carbon (GAC) has seldom been investigated. The present study focused on a green and readily synthesized Fe-Mn bimetallic oxide doped GAC (Fe-Mn@GAC), to uncover its catalytic kinetics and mechanism when used in the peroxydisulfate (PDS)-based oxidation process for degrading Rhodamine B (RhB), a representative xenobiotic dye. The synthesized Fe-Mn@GAC was characterized by SEM-EDS, XRD, ICP-OES and XPS analyses to confirm its physicochemical properties. The catalytic kinetics of Fe-Mn@GAC+PDS system were evaluated under varying conditions, including PDS and catalyst dosages, solution pH, and the presence of anions. It was found Fe-Mn@GAC exhibited robust catalytic performance, being insensitive to a wide pH range from 3 to 11, and the presence of anions such as Cl-, SO4 2-, NO3 - and CO3 2-. The catalytic mechanism was investigated by EPR and quenching experiments. The results indicated the catalytic system processed a non-radical oxidation pathway, dominated by direct electron transfer between RhB and Fe-Mn@GAC, with singlet oxygen (1O2) playing a secondary role. The catalytic system also managed to maintain a RhB removal above 81 % in successive 10 cycles, and recover to 89.5 % after simple DI water rinse, showing great reusability. The catalytic system was further challenged by real dye-containing wastewater, achieving a decolorization rate of 84.5 %. This work not only provides fresh insight into the kinetics and mechanism of the Fe-Mn@GAC+PDS catalytic system, but also demonstrates its potential in the practical application in real dye-containing wastewater treatment.

Synthesis and characterization of Co(II) porphyrin complex supported on chitosan/graphene oxide nanocomposite for efficient green oxidation and removal of Acid Orange 7 dye

Catalytic degradation of Acid Orange 7 (AO7) by hydrogen peroxide in an aqueous solution has been investigated using cobalt(II) complex of 5, 10, 15, 20 Tetrakis [4-(hydroxy)phenyl] porphyrin [Co(II) TPHPP] covalently supported chitosan/Graphene Oxide nanocomposite [Co(II) TPHPP]-Cs/GO, as highly efficient and recoverable heterogeneous catalyst. The structures and properties of [Co(II) TPHPP]-Cs/GO nanocomposite were characterized by techniques such as UV-Vis, FT-IR, SEM, EDX, TEM, and XRD. The oxidation reaction was followed by recording the UV-Vis spectra of the reaction mixture with time at λmax = 485 nm. [Co(II) TPHPP]-Cs/GO nanocomposite demonstrated high catalytic activity and could decompose 94% of AO7 within 60 min. The factors that may influence the oxidation of Acid Orange 7, such as the effect of reaction temperature, pH, concentration of catalyst, Acid Orange 7, and hydrogen peroxide, have been studied. The results of total organic carbon analysis (TOC) showed 50% of dye mineralization under mild reaction conditions of AO7 (1.42 × 10-4M) with H2O2 (8 × 10-2M) in the presence of [Co(II) TPHPP]-Cs/GO nanocomposite (15 × 10-3 g/ml) and pH = 9 at 40 °C. The reuse and stability of the nanocomposite were examined and remarkably, even after six cycles of reuse, there was no significant degradation or deactivation of the recycled catalyst. Residual organic compounds in the reaction mixture were identified by using GC-MS analyses. The radical scavenging measurements and photoluminescence probing technology of disodium salt of terephthalic acid indicated the formation of the hydroxyl radical as the reactive oxygen species in the [Co(II) TPHPP]-Cs/GO nanocomposite/H2O2 system. A mechanism for the oxidation reaction has been discussed.

An Overview on Composite Sorbents Based on Polyelectrolytes Used in Advanced Wastewater Treatment

Advanced wastewater treatment processes are required to implement wastewater reuse in agriculture or industry, the efficient removal of targeted priority and emerging organic & inorganic pollutants being compulsory (due to their eco-toxicological and human health effects, bio-accumulative, and degradation characteristics). Various processes such as membrane separations, adsorption, advanced oxidation, filtration, disinfection may be used in combination with one or more conventional treatment stages, but technical and environmental criteria are important to assess their application. Natural and synthetic polyelectrolytes combined with some inorganic materials or other organic or inorganic polymers create new materials (composites) that are currently used in sorption of toxic pollutants. The recent developments on the synthesis and characterization of composites based on polyelectrolytes, divided according to their macroscopic shape-beads, core-shell, gels, nanofibers, membranes-are discussed, and a correlation of their actual structure and properties with the adsorption mechanisms and removal efficiencies of various pollutants in aqueous media (priority and emerging pollutants or other model pollutants) are presented.