Degradation of organic contaminants into less toxic substances is the best option to remove these compounds rather than using conventional techniques. The sulfate radical-based-advanced oxidation process is an effective strategy that degrades organic contaminants by activating peroxymonosulfate (PMS). Such a strategy generates singlet oxygen (¹O₂), hydroxyl ( $$^ \bullet \!{{{\mathrm{OH}}}}$$∙OH ), and sulfate ( $${{{\mathrm{SO}}}}_4^{ \bullet\! - }$$SO4∙− ) radicals. $${{{\mathrm{SO}}}}_4^{ \bullet \!- }$$SO4∙− is distinguished by its high oxidation selectivity and activity toward the degradation of organic contaminates compared to other radicals. Various catalysts are employed in PMS activation including layered doubled hydroxides (LDHs), which are characterized by their facile synthesis and high catalytic activity. This review article is the first attempt to compile the recent progress in the degradation of common organic pollutants including aromatic compounds, pharmaceutical residues, and dyes via the PMS activation using LDH-based catalysts. The degradation pathways, reaction parameters’ influence, stability of LDHs, and comparisons between different LDH-based catalysts are investigated in this work.

In this investigation, we aimed to fabricate easy separable composite microbeads for efficient adsorption of tetracycline (TC) drug. MIL-125(Ti)/MIL-53(Fe) binary metal organic framework (MOF) was synthetized and incorporated with carbon nanotube (CNT) into alginate (Alg) microbeads to form MIL-125(Ti)/MIL-53(Fe)/CNT@Alg composite microbeads. Various tools including FTIR, XRD, SEM, BET, Zeta potential and XPS were applied to characterize the composite microbeads. It was found that the specific surface area of MIL-125(Ti)/MIL-53(Fe)/CNT@Alg microbeads was 273.77 m²/g. The results revealed that the adsorption of TC augmented with rising CNT proportion up to 15 wt% in the microbeads matrix. In addition, the adsorption process followed the pseudo-second-order and well-fitted to Freundlich and Langmuir models with a maximum adsorption capacity of 294.12 mg/g at 25 ◦C and pH 6. Furthermore, thermodynamic study clarified that the TC adsorption process was endothermic, random and spontaneous. Besides, reusability test signified that MIL-125(Ti)/MIL-53(Fe)/CNT@Alg composite microbeads retained superb adsorption properties for six consecutive cycles, emphasizing its potentiality for removing of pharmaceutical residues.

In this investigation, new porous adsorbent beads were formulatedviathe incorporation of graphene oxide (GO) into cellulose acetate beads (CA) for the adsorptive removal of methylene blue (MB) dye. The experimental results signified that the adsorption of MB dye increased with the increase in the GO ratio from 10 to 25%. In addition, the adsorption process obeyed PSO kinetic model and Langmuir isotherm model with a maximum adsorption capacity reaching 369.85 mg/g. More importantly, it was proposed that the adsorption mechanism of MB dye onto GO@CA proceeded via electrostatic interactions, H-bonding, van der Waals forces, n-π and π -π interactions. Besides, the fabricated beads exhibited an excellent ability to recycle and reuse after five successive cycles. In addition, there was a high selectivity of GO@CA beads towards MB molecules in the presence of co-existing cations such as Fe²⁺, Zn²⁺, Cu²⁺and Ni²⁺.

Water pollution is a dreadful affair that has incessantly aggravated, exposing our planet to danger. In particular, the persistent nitro aromatic compound like nitrophenols causes anxiety to the researchers due to their hazardous impacts, excessive usage, and removal difficulty. For this purpose, a novel multi-featured composite was constructed based on κ-Carrageenan (κ-Carr), MOF (MIL-125(Ti)), and magnetic Fe₃O₄ for efficient adsorptive removal of o-nitrophenol (o-NP). Interestingly, BET measurements revealed the high surface area of Fe₃O₄-κ-Carr/MIL-125(Ti) of about 163.27 m²/g, while VSM showed its excellent magnetic property (20.34 emu/g). The comparison study pointed out the synergistic effect between Fe₃O₄, κ-Carr, and MIL-125(Ti), forming a composite with an excellent adsorption performance toward o-NP. The adsorption data obeyed pseudo-second-order kinetic model, and Freundlich isotherm model was better fitted than Langmuir and Temkin. Furthermore, Langmuir verified the supreme adsorption capacity of o-NP onto Fe₃O₄-κ-Carr/MIL-125(Ti) since the computed q_max reached 320.26 mg/g at pH 6 and 25 °C. Furthermore, the XPS results postulated that the adsorption mechanism pf o-NP proceeded via H-bonding, π-π interaction, and electron donor–acceptor interactions. Interestingly, Fe₃O₄-κ-Carr/MIL-125(Ti) composite retained good adsorption characteristics after reusing for five cycles, suggesting its viable applicability as an efficient, renewable, and easy-separable adsorbent for removing nitro aromatic pollutants.