Facile synthesis of magnetic CS-g-SPSS microspheres via electron beam radiation for efficient removal of methylene blue

Antibacterial, antioxidant, Cr(VI) adsorption and dye adsorption effects of biochar-based silver nanoparticles‑sodium alginate-tannic acid composite gel beads

Ultrasonic extraction of Osmanthus fragrans was used for reducing Ag+ to prepare AgNPs, which were further loaded on barley distiller's grains shell biochar. By supplementary of sodium alginate and tannic acid, composite gel beads were prepared. The physical properties of biochar-based AgNPs‑sodium alginate-tannic acid composite gel beads (C-Ag/SA/TA) were characterized. SEM, FTIR, and XRD showed that biochar-based AgNPs were compatible with sodium alginate-tannic acid. CAg greatly improved the dissolution, swelling, and expansion of gel beads. Through the analysis by the agar diffusion method, C-Ag/SA/TA gel beads had high antibacterial activity (inhibition zone: 22 mm against Escherichia coli and 20 mm against Staphylococcus aureus). It was observed that C-Ag/SA/TA composite gel beads had high antioxidant capacity and the free radical scavenging rate reached 89.0 %. The dye adsorption performance of gel beads was studied by establishing a kinetic model. The maximum adsorption capacities of C-Ag/SA/TA gel beads for methylene blue and Congo red were 166.57 and 318.06 mg/g, respectively. The removal rate of Cr(VI) reached 96.4 %. These results indicated that the prepared composite gel beads had a high adsorption capacity for dyes and metal ions. Overall, C-Ag/SA/TA composite gel beads were biocompatible and had potential applications in environmental pollution treatment.

Green Preparation of Aminated Magnetic PMMA Microspheres via EB Irradiation and Its Highly Efficient Uptake of Ce(III)

The modification of polymers can significantly improve the ability to remove rare earth ions from wastewater, but so far few studies have focused on the irradiation-induced grafting method. In this study, a novel magnetic chelating resin for Ce(III) uptake was first synthesized by suspension polymerization of PMMA@Fe₃O₄ microspheres followed by irradiation-induced grafting of glycidyl methacrylate (GMA) and subsequent amination with polyethyleneimine (PEI). The FT-IR, SEM, TG and XRD characterization confirmed that we had successfully fabricated magnetic PMMA-PGMA-PEI microspheres with a well-defined structure and good thermal stability. The obtained adsorbent exhibited a satisfactory uptake capacity of 189.81 mg/g for Ce(III) at 318.15 K and an initial pH = 6.0. Additionally, the impact of the absorbed dose and GMA monomer concentration, pH, adsorbent dosage, contact time and initial concentration were thoroughly examined. The pseudo-second order and Langmuir models were able to describe the kinetics and isotherms of the adsorption process well. In addition, the thermodynamic data indicated that the uptake process was spontaneous and endothermic. Altogether, this research enriched the Ce(III) trapping agent and provided a new method for the removal rare earth pollutants.

Effect of Biochar Modification by Vitamin C, Hydrogen Peroxide or Silver Nanoparticles on Its Physicochemistry and Tetracycline Removal

Chemical modification of biochars can improve their adsorption capacity relative to antibiotics, posing a serious threat to the environment. Therefore, this research is aimed at the treatment of sunflower husk biochar (BC) by vitamin C, hydrogen peroxide or silver nanoparticles and the impact of this procedure on the biochar porosity, surface chemistry, and ability to remove tetracycline (TC). During the study, BC was produced by pyrolysis of sunflower husks at 650 °C. All solids were characterized using potentiometric titration, nitrogen adsorption/desorption, Fourier transform infrared spectroscopy, etc. The experimental adsorption data was described by kinetics equations: pseudo-first order, pseudo-second order, and particle internal diffusion (IPD) models as well as by isotherms of Langmuir, Langmuir-Freundlich, and Redlich-Peterson. The obtained results indicated that the biochar upgraded by vitamin C (BCV) had the highest ability to attract antibiotic molecules and, as a result, the TC adsorption on its surface was the largest. Furthermore, the TC desorption from this material was minimal. The measured TC adsorbed amounts for the modified BCs were as follows: 47.75% (7.47 mg/g) for BCV, 37.35% (8.41 mg/g)-for biochar treated by hydrogen peroxide (BCH), and 42.04% (9.55 mg/g) for biochar modified by silver nanoparticles (BCA). The lowest adsorption level was noted for non-modified biochar, i.e., 34.17% (6.83 mg/g). Based on the presented results it can be stated that the upgraded biochars had a good potential to improve the tetracycline removal from aqueous media, e.g., groundwater.

Facile Synthesis of Sustainable Tannin/Sodium Alginate Composite Hydrogel Beads for Efficient Removal of Methylene Blue

To meet the requirement of sustainable development, bio-based adsorbents were developed for the removal of dye contaminant. To improve the adsorption capacity of pure sodium alginate (SA) adsorbent for the removal of methylene blue (MB), aromatic bio-based tannin (Tan) was incorporated through the cross-linking with calcium ion. The obtained Tan/SA composite hydrogel beads were characterized with SEM, FTIR and TG, demonstrating that millimeter-sized beads were obtained through calcium cross-linking with enhanced thermal stability. The maximum capacity (247.2 mg/g) at optimal condition (pH = 12, T = 45 °C) was obtained for the 40%Tan/SA adsorbents, with a removal efficiency of 82.4%. This can be ascribed to the electrostatic attraction between SA and MB, as well as the formation of π–π stacking between Tan and MB. The adsorption process for MB is endothermic, and chemical adsorption, the removal efficiency was exceeded 90% after five cycles.

Efficient Removal of Methylene Blue by Bio-Based Sodium Alginate/Lignin Composite Hydrogel Beads

Dye pollution is a serious issue in current environment protection, and bio-based adsorbents have been receiving much attention in wastewater treatment, due to their low cost, renewable, and environmentally friendly characteristics. Bio-based sodium alginate/lignin composite (SA/Lig) hydrogel beads were fabricated by a facile cross-linking with calcium ion and used for the removal of methylene blue (MB). The obtained SA/Lig microbeads were characterized with SEM, FTIR, and TG, and the effect of lignin content, pH, and temperature on the MB adsorption was investigated. The results indicated that the introduction of aromatic lignin can not only enhance thermal stability but also can improve the adsorption performance. Under optimal conditions, the maximum adsorption capacity (254.3 mg/g) was obtained for the SA/Lig-20% beads, with a removal efficiency of 84.8%. The adsorption process for MB is endothermic, and the rate-limiting step is chemical adsorption. The removal efficiency is higher than 90% after five cycles, revealing that the prepared beads show good regeneration ability.

Design, Synthesis and Adsorption Evaluation of Bio-Based Lignin/Chitosan Beads for Congo Red Removal

The morphology and intermolecular interaction are two of the most important factors in the design of highly efficient dye adsorbent in the industry. Millimeter-sized, bead-type, bio-based lignin/chitosan (Lig/CS) adsorbent was designed for the removal of Congo red (CR), based on the electrostatic attraction, π-π stacking, and hydrogen bonding, which were synthesized through the emulsification of the chitosan/lignin mixture followed by chemical cross-linking. The effects of the lignin/chitosan mass ratio, initial pH, temperature, concentration, and contact time on the adsorption were thoroughly investigated. The highest adsorption capacity (173 mg/g) was obtained for the 20 wt% Lig/CS beads, with a removal rate of 86.5%. To investigate the adsorption mechanism and recyclability, an evaluation of the kinetic model and an adsorption/desorption experiment were conducted. The adsorption of CR on Lig/CS beads followed the type 1 pseudo-second-order model, and the removal rate for CR was still above 90% at five cycles.