Nanomaterials are promising candidates to overcome the water quality issues caused by dye consuming industries. However, their restricted efficiency in water treatment hinders their practical applications, particularly in the case of dispersed nanomaterials used in water systems. This study presents a novel approach for immobilizing ferromagnetic nanocomposites on a polymeric microporous structure. 100 mg L⁻¹ Zn_0.5Mn_0.5Fe₂O₄ nanocomposites (NCPs) were embedded into poly(methyl methacrylate) (PMMA), eliminating the need to retrieve the dispersed nanomaterials after water treatment. The developed Zn_0.5Mn_0.5Fe₂O₄–PMMA nanocomposite was characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The removal of two commercial dyes (Brilliant Blue and Allura Red) at concentration levels of (0, 25, 35, 50, 70, and 100 mg L⁻¹) was examined by batch adsorption studies followed by ultraviolet-visible (UV-vis) spectrophotometry quantification. It was observed that the maximum removal percentage was obtained for the embedded Zn_0.5Mn_0.5Fe₂O₄ nanoparticles on the PMMA polymer using 100 mg of Zn_0.5Mn_0.5Fe₂O₄ NCPs for all the four dye levels in comparison to dispersed Zn_0.5Mn_0.5Fe₂O₄ nanocomposites. It was observed that the maximum adsorption of Brilliant Blue and Allura Red was obtained under alkaline conditions, pH 7.32 and 8.37, respectively. It was suggested that Zn_0.5Mn_0.5Fe₂O₄–PMMA can be applied as a sustainable material to enhance water treatment efficiency by merging the advantages of a fast preparation technique and a higher adsorption capacity to remove complex organic contaminants.

A biosurfactant-producing isolate, Bacillus subtilis AHV-KH11, was used for the biodegradation of diesel-contaminated saline soils. In addition to naturally occurring diesel contamination, the collected soil samples were artificially contaminated with diesel oil at concentrations ranging from 1000 to 5000 mg kg^− 1 of soil. The operational parameters investigated in our experiment were the initial seed volume (5–20 mL), soil moisture content (100–300%), external surfactants (rhamnolipid and Tween 80), and salinity levels (0.5–2%). The results indicated that diesel biodegradation was optimized at an initial seed volume of 10 mL, while further increases up to 20 mL provided no additional benefit. This suggests that diesel biodegradation can be effectively initiated with a relatively modest bacterial inoculum. This study demonstrates how the remediation process enhances the salinity tolerance of Bacillus subtilis AHV-KH11, achieving effective remediation at 1.5% salinity without an external surfactant and enhanced performance at 8% salinity when exogenous rhamnolipid is added. The addition of rhamnolipid as an external biosurfactant increased the diesel biodegradation rate. In addition to accelerating diesel degradation, rhamnolipid significantly improved soil health, as demonstrated by toxicity assays using Eisenia fetida, the mortality rate dropped from 88% in untreated diesel-contaminated soil to 41% in bioremediated soil after 14 days. Furthermore, the salt tolerance of Bacillus subtilis AHV-KH11 can be enhanced, highlighting its potential as an efficient diesel decomposer and biosurfactant producer in pure or mixed cultures for the bioremediation of diesel-contaminated saline soils.