Magnetic aminated lignin/CeO2/Fe3O4 composites with tailored interfacial chemistry and affinity for selective phosphate removal.

Phosphorus (P) has brought a series of environmental problems while benefiting mankind. To reclaim phosphorus from wastewater efficiently and conveniently, a novel magnetic adsorbent with aminated lignin/CeO2/Fe3O4 composites (AL-NH2@Fe3O4-Ce) possessing a high affinity to phosphate and easily separated from aqueous solutions was developed in this work. The characterization results revealed that Fe and Ce elements have been doped into the aminated lignin successfully. Batch experiment results convinced that the maximum phosphate adsorption capacity of AL-NH2@Fe3O4-Ce was 183.72 mg P/g at pH = 3, which was roughly 4.5 times greater than aminated lignin and 8.5 times greater than cerium oxide, respectively. The adsorption isotherm was fitted well by the Langmuir model, and the adsorption kinetics was in line with the pseudo-second-order model. The adsorption thermodynamics indicated the adsorption process was spontaneous and naturally exothermic. Additionally, AL-NH2@Fe3O4-Ce exhibited high selectivity towards phosphate over common coexisting anions (Cl-, NO3-, HCO3-, SO42- and F-). After five consecutive cycles, the adsorption performance of AL-NH2@Fe3O4-Ce decreased by only 16% compared with the fresh adsorbent, indicating that AL-NH2@Fe3O4-Ce exhibited excellent recycling ability. The results of XPS analysis and batch experiments showed that the possible mechanisms were electrostatic attraction and inner-sphere complexation. The tailored interfacial chemistry affinity to phosphate as well as endowed magnetic property reveled AL-NH2@Fe3O4-Ce could be adopted as an up and coming adsorbent in phosphate removal process.

Adsorption of Cr(VI), Ni(II), Fe(II) and Cd(II) ions by KIAgNPs decorated MWCNTs in a batch and fixed bed process.

The efficient removal of toxic metals ions from chemical industry wastewater is considered problematic due to the existence of pollutants as mixtures in the aqueous matrix, thus development of advanced and effective treatment method has been identified as a panacea to the lingering problems of heavy metal pollution. In this study, KIAgNPs decorated MWCNTs nano adsorbent was developed using combination of green chemistry protocol and chemical vapor deposition techniques and subsequently characterized using UV-Vis, HRTEM, HRSEM, XRD, FTIR and XPS. The adsorptive efficiency of MWCNTs-KIAgNPs for the removal of Cr(VI), Ni(II), Fe(II), Cd(II) and physico-chemical parameters like pH, TDS, COD, BOD, nitrates, sulphates, chlorides and phosphates from chemical industrial wastewater was examined in both batch and fixed bed systems. The result exhibited successful deposition of KIAgNPs on the surface of MWCNTs as confirmed by the microstructures, morphology, crystalline nature, functional groups and elemental characteristics of the MWCNTs-KIAgNPs. Optimum batch adsorption parameters include; pH (3 for Cr(VI) and 6 for Ni(II), Fe(II) and Cd(II) ions), contact time (60 min), adsorbent dosage (40 mg) and temperature (318 K). The binding capacities were obtained as follows; Cr6+ (229.540 mg/g), Ni2+ (174.784 mg/g), Fe2+ (149.552) and Cd2+ (121.026 mg/g), respectively. Langmuir isotherm and pseudo-second order kinetic model best described the experimental data in batch adsorption, while the thermodynamic parameters validated the chemisorption and endothermic nature of the adsorption process. In continuous adsorption, the metal ions were effectively removed at low metal influent concentration, low flow rate and high bed depth, whereby the experimental data were designated by Thomas model. The high physico-chemical parameters in the wastewater were successfully treated in both batch and fixed bed systems to fall within WHO permissible concentrations. The adsorption/desorption study illustrated over 80% metal removal by MWCNTs-KIAgNPs even after 8th adsorption cycle. This study demonstrated excellent performance of MWCNTs-KIAgNPs for chemical industry wastewater treatment.

Multistage reclamation of Co2+-containing alginate hydrogels as excellent reduction catalyst and subsequent microwave absorber by facile transformation.

The multistage reclamation of materials has made contributions to sustainable development, but further progress is still sought after. In this work, functionalized seaweed-based composites were successfully prepared and utilized in multiple stages. Specifically, Co2+-containing alginate hydrogels (CHB-Co2+) prepared by sol-gel self-assembly and adsorption method using interior/exterior co-functionalized calcium alginate as raw materials were utilized for efficient reduction of p-nitrophenol. After coupling with freeze-drying and carbonization procedures, a high-performance Co/N co-doped carbonaceous microwave absorber was obtained and investigated in detail. By virtue of unique 3D interconnected network, heterogeneous interfaces and doped heteroatom N species, by which endowing the absorber with optimal impedance matching and attenuation ability, as-fabricated NC-Co-700 exhibited prominent microwave absorption performance with -54.2 dB of RLmin at 6.4 GHz and 5.3 GHz of maximum absorption bandwidth (from 12.7 to 18.0 GHz). Additionally, in view of the dielectric loss and magnetic loss caused by the synergy effect among the functional components, the underlying absorption mechanism was proposed. This work provided a novel idea for designing biomass-based functional materials and simultaneously achieved economic benefits through the rational utilization of other products in the preparation process.

Interior engineering of seaweed-derived N-doped versatile carbonaceous beads with Co x O y for universal organic pollutant degradation.

The rational optimization of catalytic composites with excellent catalytic activities and long-term cycling stabilities for environmental remediation is still maintained as highly desired but is an ongoing challenge. Here, seaweed-derived N-doped versatile carbonaceous beads with Co x O y (Co-NC-0.25-700 °C) are employed as a novel catalyst to activate peroxymonosulfate (PMS) for methylene blue (MB) degradation. Profiting from the improved structure-activity relationship and the synergistic effects between the "egg-box" structure and the Co x O y loaded on the N-doped carbonaceous beads, Co-NC-0.25-700 °C exhibited relatively high performance and comparative long-term stability. The universal applicability of Co-NC-0.25-700 °C was investigated by degrading other types of organic pollutants in various systems. For this type of newly fabricated high-performance versatile composites, structure-property relationships were plausibly proposed. Notably, the degradation efficiency and the catalyst structure could be tailored by the amount of polyethyleneimine (PEI) introduced in the preparation process and by the pyrolysis temperature. More favorably, the coupling of the magnetic properties and bead-like shape endows the resultant composites with remarkable reusability and recyclability, as compared to powder state materials. Another interesting finding is that MB degradation over Co-NC-0.25-700 °C is minimally affected by common ions (Cl-, NO3 -, SO4 2-, etc.), and holds a certain catalytic activity under the background conditions of two simulated real water conditions (running water and seawater). Of particular interest, a microreactor filled with Co-NC-0.25-700 °C was utilized as a verification model for practical applications of the reaction in continuous-flow. More far-reaching, the simulations of actual water conditions and the design of a continuous-flow reactor represent a giant step towards universal applications for organic pollution treatment.