Recyclable adsorbents based on Fe3O4 nanoparticles on lanthanum-modified montmorillonite for the efficient phosphate removal

Investigation of the Adsorption Process of Chromium (VI) Ions from Petrochemical Wastewater Using Nanomagnetic Carbon Materials

Magnetic mesoporous carbon (MMC) and magnetic activated carbon (MAC) are good functionalized carbon materials to use when applying environmental techniques. In this work, a series of efficient magnetic composite adsorbents containing Fe₃O₄ and carbon were prepared successfully and used for the adsorption of Cr(VI) ions in petrochemical wastewater. The morphology and structure of these magnetic adsorbents were characterized with FTIR, TG, XRD, VSM, BET, and SEM technologies. The effect of different factors, such as pH, adsorption time, initial Cr(VI) ions' concentration, Fe₃O₄ loading, and adsorption time, on the adsorption behavior were discussed. The results showed that the 8%Fe₃O₄@MMC adsorbent exhibited a high removal rate, reutilization, and large adsorption capacity. The corresponding adsorption capacity and removal rate could reach 132.80 mg·g^-1 and 99.60% when the pH value, adsorption time, and initial Cr(VI) ions' concentration were 2, 180 min, and 80 mg·L^-1 at 298 K. Four kinds of adsorption isotherm models were used for fitting the experimental data by the 8%Fe₃O₄@MMC adsorbent at different temperatures in detail, and a kinetic model and thermodynamic analysis also were performed carefully. The reutilization performance was investigated, and the Fe₃O₄@MMC adsorbent exhibited greater advantage in the adsorption of Cr(VI) ions. These good performances can be attributed to a unique uniform pore structure, different crystalline phases of Fe₃O₄ particles, and adsorption potential rule. Hence, the 8%Fe₃O₄@MMC adsorbent can be used in industrial petrochemical wastewater treatment.

Phosphate removal from actual wastewater via La(OH)3-C3N4 adsorption: Performance, mechanisms and applicability

In this study, La(OH)₃ nanoparticles were immobilized on C₃N₄ to effectively restrict their aggregation and subsequently enhance the La utilization efficiency to promote phosphate adsorption. The prepared La(OH)₃-C₃N₄ nanocomposite was characterized by SEM, XRD, FTIR, XPS, BET and Zeta potential analysis. Batch and continuously-fed (fixed-bed column) experiments to assess the adsorption performance of La(OH)₃-C₃N₄ showed that the composite exhibits superior utilization efficiency, resulting to relatively quick adsorption with a short equilibrium time of 30 min. The theoretical maximum P adsorption capacity reached the 148.35 mg·g^-1, efficiency that remained unaffected by the anions and HA present. The adsorption mechanism showed stability in a wide pH range (4.0-11.0) and is considered effective even after extensive use (five-cycles). The dynamics of the adsorption capacity and the half-penetration time values were estimated by 'Thomas' and 'Yoon-Nelson' models showed that are better represented from the experimental values obtained from the fixed-bed column trial. The adsorption mechanisms were attributed to surface precipitation, electrostatic attraction, and inner-sphere complexation via ligand exchange. Furthermore, La(OH)₃-C₃N₄ demonstrated high efficiency in scavenging phosphate from both diluted and concentrated wastewater (natural pond and swine wastewater respectively). The above confirm that La(OH)₃-C₃N₄ is a promising composite material for phosphate management in aqueous environments.