This study focusses on the synthesis of silver nanoparticles (Ag-nPs) by citrus fruit (Citrus paradisi) peel extract as reductant while using AgNO₃ salt as source of silver ions. Successful preparation of biogenic CAg-nPs catalyst was confirmed by turning the colorless reaction mixture to light brown. The appearance of surface Plasmon resonance (SPR) band in UV-Vis spectra further assured the successful fabrication of nPs. Different techniques such as FTIR, TGA and DLS were adopted to characterize the CAg-nPs. CAg-nPs particles were found to excellent catalysts for reduction of Congo red (CR), methylene blue (MB), malachite green (MG), Rhodamine B (RhB) and 4-nitrophenol (4-NP). Reduction of CR was also performed by varying the contents of NaBH₄, CR and catalyst to optimize the catalyst activity. The pseudo first order kinetic model was used to explore the value of rate constants for reduction reactions. Results also interpret that the catalytic reduction of dyes followed the Langmuir–Hinshelwood (LH) mechanism. According to the LH mechanism, the CAg-nPs role in catalysis was explained by way of electrons transfer from donor (NaBH₄) to acceptor (dyes). Due to reusability and green synthesis of the CAg-nPs catalyst, it can be a promising candidate for the treatment of water sources contaminated with toxic dyes.

Water-stable zeolitic imidazolate frameworks (ZIF) with zinc and cobalt cations were synthesized to explore the effect of metal ions on arsenic adsorption. At room temperature (25 2 ºC) and pH 7.8, maximum adsorption capacities of arsenic (As5+) on the surface of ZIF-8 and ZIF-67 were 87.03 and 86.70 mg g-1 respectively, with encouraging results up to 95% reusability of the adsorbents. The results of this study revealed that electrostatic attraction and ion exchange were the major mechanisms responsible for better efficiencies for adsorptive removal of arsenic. The evidence for the adsorption of arsenic contaminants was confirmed by FTIR analyses. The pseudo second order and Langmuir models were best suited to explain the adsorption of arsenic species on the surface of the as-synthesized metal-organic frameworks (MOFs). Based on the results, it was possible to conclude that the metal atoms in the synthesized MOFs had a minor impact on adsorption, since these MOFs presented identical results in the removal of arsenic species. This observation can be explained by the presence of a similar organic linker (2-methyl imidazole), which points to almost the same geometry and sponginess. However, there was a slight difference in the adamsite (organo-arsenic) removal achieved by the MOFs with different metal atoms.

Water is a basic unit for survival of living creature and over the past few years, increased industrialization and urbanization caused a huge contamination of natural water resources. Major water contaminants are pharmacological-wastes, especially antibiotics from hospitals and pharmaceutical industries which causes water pollution. Pharmacological contaminants elimination from ecosystem is very critical environmental challenge because they are persistent and cause potential health hazards. Owing to high surface area, tunable-porosity, and versatile functionality of Metal-Organic Frameworks (MOFs), and their composites have emerged as promising materials for water purification. Various antibiotics including amoxicillin, doxycycline, levofloxacin, and ciprofloxacin are successfully removed from wastewater using MOFs and composites, which purifies the water by adsorption-mechanism. This study reviews the advanced progressions in the application of MOF-based composites and MOFs for the adsorption of pharmaceutical pollutants. Additionally, plant-based MOFs have been explored for their eco-friendly and cost-effective potential in pharmaceutical pollutant removal. Despite these advancements, challenges such as the scalability of MOF synthesis, stability under operational conditions, and potential toxicity need to be addressed for their commercial application. Future research should focus on optimizing the synthesis processes, enhancing the recyclability of MOFs, and conducting long-term environmental-impact assessments to ensure sustainable and effective water treatment solutions.