For applications involving water cleanup, metal oxide nanoparticles are exceptionally successful. They are useful for the adsorption and photocatalytic destruction of organic pollutants due to their distinctive qualities, which include their wide surface/volume area, high number of active sites, porous structure, stability, recovery, and low toxicity. Metal oxide nanomaterials have drawn a lot of attention from researchers in the past ten years because of their various production pathways, simplicity in surface modification, abundance, and inexpensive cost. A wide range of metal oxides, such as iron oxides, MgO, TiO₂, ZnO, WO₃, CuO, Cu₂O, metal oxides composites, and graphene–metal oxides composites, with variable structural, crystalline, and morphological features, are reviewed, emphasizing the recent development, challenges, and opportunities for adsorptive removal and photocatalytic degradation of organic pollutants such as dyes, pesticides, phenolic compounds, and so on. In-depth study of the photocatalytic mechanism of metal oxides, their composites, and photocatalytically important characteristics is also covered in this paper. Metal oxides are particularly effective photocatalysts for the degradation of organic pollutants due to their high photodegradation efficiency, economically sound methods for producing photo-catalytic materials, and precise band-gap engineering. Due to their detrimental effects on human health, pesticides—one of the highly hazardous organic pollutants—play a significant part in environmental contamination. Depending on where they come from and who they are targeting, they are categorized in various ways. Researchers focusing on metal oxides and their composites for the adsorptive and photocatalytic degradation of pesticides would find the review to be a beneficial resource. Detailed information on many pesticides, difficulties associated with pesticides, environmental concentration, and the necessity of degradation has been presented.

Hazardous chemicals like toxic organic dyes are very harmful to the environment and their removal is quite challenging. Therefore there is a necessity to develop techniques, which are environment friendly, cost-effective and easily available in nature for water purification and remediation. The present research work is focused on the development` and characterization of the ecofriendly semi-interpenetrating polymer network (semi-IPN) nanocomposite hydrogels composed of polyvinyl alcohol (PVA) and alginate (Alg) hydrogel beads incorporating natural bentonite (Bent) clay as a beneficial adsorbent for the removal of toxic methylene blue (MB) from aqueous solution. PVA−Alg/Bent nanocomposite hydrogel beads with different Bent content (0, 10, 20, and 30 wt%) were synthesized via external ionic gelation method. The designed porous and steady structure beads were characterized by the use of Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). The performance of the beads as MB adsorbents was investigated by treating aqueous solutions in batch mode. The experimental results indicated that the incorporation of Bent (30 wt%) in the nanocomposite formulation sustained the porous structure, preserved water uptake, and increased MB removal efficiency by 230% compared to empty beads. Designed beads possessed higher affinity to MB at high pH 8, 30 °C, and fitted well to pseudo-second-order kinetic model with a high correlation coefficient. Moreover, the designed beads had good stability and reusability as they exhibited excellent removal efficiency (90%) after six consecutive adsorption-desorption cycles. The adsorption process was found be combination of both monolayer adsorption on homogeneous surface and multilayer adsorption on heterogeneous surface. The maximum adsorption capacity of the designed beads system as calculated by Langmuir isotherm was found to be 51.34 mg/g, which is in good agreement with the reported clay-related adsorbents. The designed semi-IPN PVA−Alg/Bent nanocomposite hydrogel beads demonstrated good adsorbent properties and could be potentially used for MB removal from polluted water.

Globally, water contamination by heavy metals is a serious problem that affects the environment and human health. Adsorption is the most efficient way of water treatment for eliminating heavy metals. Various hydrogels have been prepared and used as adsorbents to remove heavy metals. By taking advantage of poly(vinyl alcohol) (PVA), chitosan (CS), cellulose (CE), and the process for physical crosslinking, we propose a simple method to prepare a PVA-CS/CE composite hydrogel adsorbent for the removal of Pb(II), Cd(II), Zn(II) and Co(II) from water. Structural analyses of the adsorbent were examined by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy-energy dispersive X-ray (SEM-EDX) analysis, and X-ray diffraction (XRD). PVA-CS/CE hydrogel beads had a good spherical shape together with a robust structure and suitable functional groups for the adsorption of heavy metals. The effects of adsorption parameters such as pH, contact time, adsorbent dose, initial concentration of metal ions, and temperature on the adsorption capacity of PVA-CS/CE adsorbent were studied. The adsorption characteristics of PVA-CS/CE for heavy metals may be completely explained by pseudo-second-order adsorption and the Langmuir adsorption model. The removal efficiency of PVA-CS/CE adsorbent for Pb(II), Cd(II), Zn(II), and Co(II) was 99, 95, 92, and 84%, respectively, within 60 min. The heavy metal’s hydrated ionic radius may be crucial in determining the adsorption preference. After five consecutive adsorption–desorption cycles, the removal efficiency remained over 80%. As a result, the outstanding adsorption-desorption properties of PVA-CS/CE can potentially be extended to industrial wastewater for heavy metal ion removal.

The continuous production and widespread applications of synthetic plastics and their waste present immense environmental challenges and damage living systems. Microplastics (MPs) have become of great concern in various ecosystems due to their high stability and decomposition into smaller fragments such as nano-plastics (NPs). Nevertheless, MPs and NPs can be removed from the environment using several physical, chemical, and microbiological methods. This study presents a comprehensive narrative literature review, which aims to explore the various types of MPs and NPs, their sources, fate, toxicity, and impact on human health and environment. To achieve this aim, the study employed a comprehensive literature review methodology. In addition, it summarizes various methods of sample collection and analysis techniques. Remediation strategies for MPs and NPs removal are assessed and compared. Furthermore, it highlights interlinkages between the sustainable development goals (SDGs)—specifically SDG 14—and plastic pollution. Overall, priority for research and development in the field of MPs and NPs impacts on ecological ecosystems is a must as this will enable the development of scientific polices driven by global collaboration and governance which in turn will develop tools and methodologies that measure the impacts and risk of plastic pollution.

Spinel ferrites nanoparticles (SNPs) have been extensively studied, synthesized and used in many applications including wastewater treatment, biosensors and as photocatalysts. The studies of the effect of these SNPs at cellular and molecular levels and their influence in the environment are scarce. Thus, in the current study, different metal ferrite SNPs were synthesized via sol-gel-combustion route and were characterized by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) with Energy Dispersive X-ray (EDX) and Vibrating Sample Magnetometry (VSM) analysis techniques. The effect of these SNPs on the growth of the microalgae Picochlorum sp. was then investigated. The results showed that the synthetic method used to prepare the metal ferrite SNPs leads to highly crystalline SNPs with average crystallites size between 33–36 nm except for ZnFe₂O₄ NPs which have crystallite size of 52 nm. The results of XRD and EDS confirmed the formation of SNPs. VSM analysis of CoFe₂O₄ showed the highest magnetic energy (U) and saturation magnetization (Ms) of 30870 erg/g and 60 emu/g, respectively. Although, the microalgae culture of Picochlorum sp. treated with different SNPs showed significant difference in viable cells concentration at 48 h and 72 h of incubation compared to control samples, the growth pattern of both treated and untreated samples were seen similar. This could indicate that SNPs may reduce the growth of the microalgae but will not cause severe inhibition when used at the proper concentration. This promotes their potential use for many applications.

Hazardous chemicals like toxic organic dyes are very harmful to the environment and their removal is quite challenging. Therefore there is a necessity to develop techniques, which are environment friendly, cost-effective and easily available in nature for water purification and re-mediation. The present research work is focused on the development` and characterization of the ecofriendly polyvinyl alcohol (PVA) and alginate (Alg) hydrogel beads incorporating natural bentonite (Bent) clay as beneficial adsorbents for removal of toxic methylene blue (MB) from industrial water. PVA−Alg/Bent nanocomposite hydrogel beads with different Bent content (0, 10, 20, and 30 wt%) were synthesized via external ionic gelation method. The designed porous and steady structure beads were characterized by the use of Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). The performance of the beads as MB adsorbents was investigated by treating batch aqueous solutions. The experimental results indicated that the incorporation of Bent (30 w%) in the nanocomposite formulation sustained porous structure, preserved water uptake, and increased MB removal effi-ciency by 230 % compared to empty beads. Designed beads possessed higher affinity to MB at high pH 8, 30 °C, and fitted well to pseudo-second-order kinetic model a high correlation coefficient. Moreover, designed beads had a good stability and reusability as they exhibited excellent removal efficiency (90%) after six consecutive adsorption-desorption cycles. Adsorption process was found be combination of both monolayer adsorption on homogeneous surface and multilayer adsorption on heterogeneous surface. The maximum adsorption capacity of the designed beads system as calculated by Langmuir isotherm was found to be 51.34 mg/g, which is in good agreement with the reported clay-related adsorbents. The designed PVA−Alg/Bent nanocomposite hydrogel beads demonstrated good adsorbent properties and could be potentially used for MB removal from polluted water.