Fly ash is a significant pollutant in thermal power stations. Although this waste harms the environment and humans, it is badly removed and managed, and only a few studies are interested in this waste. For that, this study aims to valorise fly ash into potential adsorbents to treat tannery effluents for the first time. The physicochemical characterisation showed that fly ash has a pHpzc of 9.78, a very porous structure, a high specific surface area of 3127.2 m²/g with a total pore volume of 3.27 cm³/g, and a high silica and aluminium percentage. SEM showed that the fly ash studied has a small particle size ranging between 32 nm and 100 μm. Batch adsorption experiments were done, and the effects of adsorption parameters were investigated. The kinetics and isotherms models indicate that the equilibriums were achieved in 30 min, where the maximum uptake capacity was 2496, 223.7 and 106.8 mg/g for Chemical Oxygen Demand (COD), chromium (VI) and sulfide ions, respectively. The kinetic data were well fitted to the pseudo-second-order model and showed that adsorption onto fly ash may be chemical and physical simultaneously. Freundlich's model gave a better fit for the experimental adsorption equilibrium data and displayed multilayer adsorption. The thermodynamic isotherm showed that the adsorption onto fly ash is thermodynamically spontaneous (ΔG° < 0) and endothermic (ΔH° > 0). In conclusion, fly ash, which is a free material, has a more robust adsorption capacity than other expensive materials. Thus, it can be a promising, eco-friendly, attractive adsorbent for industrial wastewater treatment.

To date, compost maturation monitoring is carried out by physical-chemical and microbiological analysis, which could be considered an overweening consumption of time and products. Nowadays, spectroscopy is chosen as a simple tool for monitoring compost maturity. In the present investigation, spectroscopy analysis was performed in the interest of corroborating the compost maturity. This goal was achieved by using the X-ray diffraction, infrared spectroscopy, and scanning electron microscopy. X-ray diffraction analysis showed the presence of the cellulose fraction in compost samples. At the same time, the intensity of pics decreased depending on composting time, thus proving that there was organic matter degradation. Infrared and scanning electron microscopy analysis allow for confirming these results. The correlation between spectroscopies analysis and physical-chemical properties was employed by partial least squares-regression (PLS-R) model. PLS-R model was applied to build a model to predict the compost quality depending on the composting time, the results obtained show that all the parameters analysis are well predicted. The current study proposed that final compost was more stabilized compared with the initial feedstock mixture. Ultimately, spectroscopy techniques used allowed us to confirm the physical-chemical results obtained, and both of them depict maturity and stability of the final compost, thus proving that spectral techniques are more reliable, fast, and promising than physical-chemical analyses.

Physicochemical and microbiological analyses of liquid hospital effluents have demonstrated that they are loaded with organic and inorganic pollutants then discharged into the sewerage networks without treatment. The aim of this study is to suggest an effective solution for their treatment. Column filtration is an adequate method to reduce the pollutant load which makes it possible to have a rate of abatement of 97% and 79% by filtering the pollutant material using sawdust of catia and red sawdust, respectively, with a filter bed height equal to 13 cm. Physicochemical parameters such as chemical oxygen demand, biological oxygen demand, nitrate, ammonia, phosphorus, electrical conductivity and the bacteriological parameters like fecal coliforms, Streptococci, and Staphylococci have been measured. The analysis of heavy metals displays compliance with the World Health Organization standards. The red sawdust and catia sawdust have been characterized by scanning electron microscopy and Fourier-transform infrared spectroscopy.