This work reports the adsorption of crystal violet (CV) dye onto magnetic zeolite (MZ) nanoparticles, synthesized by direct fusion of fly ash (FA) and magnetite particles. The synthesised MZ showed high capacity for CV dye adsorption, removing 95% of the dye at an equilibrium adsorption time of 10 min and 25˚C. The effects of adsorbent dosage, dye concentration, and pH, on adsorption were evaluated. Adsorption data were best described by the Langmuir adsorption isotherm (R 2 = 0.9986), while the adsorption kinetics was best fitted by the pseudo-second-order kinetic model (R 2 = 0.9999). Application of the MZs synthesised from inexpensive resources such as FA could ensure the sustainability and cost effectiveness of treating industrial effluent containing basic dyes, especially effluent from the textile industries.

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An alkali-tolerant bacterium, Pseudomonas aeruginosa STK 03 (accession number KR011154), isolated from an oil spill site, was evaluated for the biodegradation of free cyanide and thiocyanate under alkaline conditions. The organism had a free cyanide degradation efficiency of 80 and 32 % from an initial concentration of 250 and 450 mg CN−/L, respectively. Additionally, the organism was able to degrade thiocyanate, achieving a degradation efficiency of 78 and 98 % from non- and free cyanide spiked cultures, respectively. The organism was capable of heterotrophic nitrification but was unable to denitrify aerobically. The organism was unable to degrade free cyanide in the absence of a carbon source, but it was able to degrade thiocyanate heterotrophically, achieving a degradation efficiency of 79 % from an initial concentration of 250 mg SCN−/L. Further increases in thiocyanate degradation efficiency were only observed when the cultures were spiked with free cyanide (50 mg CN−/L), achieving a degradation efficiency of 98 % from an initial concentration of 250 mg SCN−/L. This is the first study to report free cyanide and thiocyanate degradation by Pseudomonas aeruginosa. The higher free cyanide and thiocyanate tolerance of the isolate STK 03, which surpasses the stipulated tolerance threshold of 200 mg CN−/L for most organisms, could be valuable in microbial consortia for the degradation of cyanides in an industrial setting.

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The suitability of Musa paradisiaca (banana) peel extract as a green corrosion inhibitor for mild steel in acidic medium (1 M HCl) was investigated using factorial method of the design of experiment. The effects of two independent variables (concentration of banana peel extract and temperature) on the corrosion inhibition efficiency were investigated. The physicochemical properties of the extract such as surface tension, viscosity, flash point, and specific gravity were determined using standardized methods provided by the American System of Testing Materials (D-971). The relationship between the independent variables and the inhibitor efficiency was modeled by gasometric and thermometric methods. The statistical analysis of the inhibition efficiency was carried out using the "Fit Regression Model" of Minitab ® 17.0, while the fitness of the models was assessed by the coefficient of determination (R 2 ) and the analysis of variance (ANOVA). From the results obtained, gasometric method achieved a maximum inhibition efficiency of 66.83%, with an R 2 of 90.76%, whereas thermometric method gave a maximum inhibition efficiency of 65.70%, with an R 2 of 95.56%. This study shows that banana peel extract has the capacity to prevent the corrosion of mild steel in acidic medium.