The sepiolite/ZrO₂ composites were prepared by sepiolite (Sep) modification with zirconium propoxide in toluene at room temperature for 24 h (Sep–ZrI) or 95 °C for 4 h (sample Sep–ZrII). The efficiency of the obtained composites for the removal of phosphate from aqueous solutions at initial pH = 4 and pH = 8 was investigated. Characterization of the samples shows that synthesis at a higher temperature for a shorter time provides a slightly higher content of amorphous Zr phase, which is deposited on the sepiolite fibers as a thin layer and agglomerated nanoparticles. Compared to Sep, the composites have a lower point of zero charge and higher specific surface area and pore volume. The adsorption kinetics follow the pseudo second-order model. The adsorption capacities of the composites are approximately the same at both initial pH and higher at initial pH = 4 than at pH = 8. The XPS and ATR-FTIR of Sep–ZrI before and after adsorption identifies the formation of inner-sphere complexes as the mechanism of phosphate adsorption. The slow release during desorption with NaOH solution confirms the strong bonds of the phosphates with the surface of the composites.

This paper investigates the influence of the air flow rate in a three-phase air-lift reactor on the sorption of toxic dye, Brilliant green, onto a promising and efficient sorbent, sour cherry stone biochar. In order to gain a comprehensive insight into the sorbent/sorption behaviour, sour cherry stone biochar was characterized by Fourier transform infrared spectroscopy with attenuated total reflection, pH of the suspension, point of zero charge, scanning electron microscopy with energy-dispersive X-ray spectroscopy and X-ray diffraction. The experiments were performed in an air-lift reactor using airflows of 2.50 and 5.55 dm3 h-1. The experimental data of sorption kinetics experiments were fitted by non-linear form of pseudo-first and, pseudo-second models as well as the Weber-Morris model based on intraparticle diffusion. The overall sorption rate was found to be limited by the Brilliant Green mass transport rate to the sorbent at a lower airflow and thus mixing intensity, while it was kinetically controlled at a higher rate following the pseudo-second order kinetic model. Furthermore, sorption at lower air flow was delayed by mass transfer resistance through the liquid boundary layer surrounding sorbent particles. Presented results clearly indicate that airflow intensity plays a significant role in the overall sorption kinetics and support possible application of the applied biochar for efficient Brilliant Green sorption.

Manure is a by-product at agricultural farms that can consist of excrement, bedding, food, and other substances. Manure is a significant form of organic fertilizer, but it negatively impacts the environment. The objectives of this study are to determine the quantities of manure and classify them depending on the size and type of farms in Serbia and to quantify greenhouse gas emissions in Serbia from manure management. About 8.6 million m3 of fresh liquid manure and about 20.4 million tons of fresh solid manure are generated in Serbia. The dominant types of manures are liquid pig manure and cattle solid and liquid manures. Approximately 81% of the total amount of manure is located at farms with less than 100 livestock units. In Serbia, at large farms with over 1,000 livestock units, about 12% of the total amount of manure is generated. In 2020, about 23 Gg of CH4 and 1 Gg of N2O were emitted directly from manure. About 1,1 Gg of N2O is emitted indirectly from manure management. Total emissions of greenhouse gases originating from manure in 2020 amounted to about 1,144 GgCO2eq. Greenhouse gas emissions are declining due to the reduction of livestock, so in comparison to 1990, they are reduced by 36% for this sector.