Environmental management through effective utilization of biowastes has been a topic of intensive research in recent years. This study examines the effect of pyrolysis temperature on the physical and morphological characteristic of biochar (BC) derived from lignocellulosic wastes. The biochar was prepared by pyrolysing date palm biomass at various temperatures, i.e., 300, 400, 500, 600, and 700 °C. These pyrolysed biochars were then characterized for their carbon content, mineral compositions, chemical functionalities, and morphological structures, for understanding their physicochemical characteristics and microstructural evolution. It was revealed that the pyrolytic condition plays a key role in the formation of biochar microstructure. These biochar samples were then utilized without any further treatments/purifications for their practical application as reinforcement materials for polymer composites. They were blended with a polypropylene matrix by a melt mixing technique followed by injection molding process. The type of biochar was found to significantly affect the composites properties. Differences in microstructure, surface chemistry, and chemical compositions of BCs were observed to be determining factors affecting the compatibility and thermomechanical properties of resulted composites.

This study includes the characterization and exploitation of an abundant agricultural waste in Algeria, Alfa (Stipa tenacissima L.) leaf powder (ALP) as a biosorbent for the removal of hazardous triphenylmethane dyes, malachite green (basic green 4) and crystal violet (basic violet 3), from aqueous media under various operating conditions in batch mode. The effect of experimental parameters such as initial dye concentration (10–40 mg/L), contact time (0–300 min), biosorbent dose (2.5–5.5 g/L), initial pH (2–8), temperature (298–328 K), and ionic strength on dye sorption was investigated. The results of both dyes show that the increase in initial concentration, contact time, temperature, and initial pH of solution leads to an increase in biosorbed quantity, unlike the effect of ionic strength. The biosorption kinetics for triphenylmethane dyes on ALP was analyzed by pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models proposed by the Weber–Morris equation. Equilibrium sorption data were analyzed by six isotherms, namely the Langmuir, Freundlich, Harkins–Jura, Flory–Huggins, Elovich, and Kiselev isotherms. The thermodynamic parameters were evaluated for both dyes. The thermodynamic results suggest that both dyes’ biosorption is a typical physical process, spontaneous and endothermic in nature.

Herein, we present an original report on chlorine activation by ultrasound (US: 600 kHz, 120 W) for intensifying the sonochemical treatment of hazardous organic materials. The coupling of US/chlorine produced synergy via the involvement of reactive chlorine species (RCSs: Cl^•, ClO^• and Cl₂^•−), resulting from the sono-activation of chlorine. The degradation of Allura Red AC (ARAC) textile dye, as a contaminant model, was drastically improved by the US/chlorine process as compared to the separated techniques. A synergy index of 1.74 was obtained by the US/chlorine process for the degradation of ARAC (C₀ = 5 mg·L⁻¹) at pH 5.5 and [chlorine]₀ = 250 mM. The synergistic index increased by up to 2.2 when chlorine concentration was 300 µM. Additionally, the synergetic effect was only obtained at pH 4–6, where HOCl is the sole chlorine species. Additionally, the effect of combining US and chlorine for ARAC degradation was additive for the argon atmosphere, synergistic for air and negative for N₂. An air atmosphere could provide the best synergy as it generates a relatively moderate concentration of reactive species as compared to argon, which marginalizes radical–radical reactions compared to radical–organic ones. Finally, the US/chlorine process was more synergistic for low pollutant concentrations (C₀ ≤ 10 mg·L⁻¹); the coupling effect was additive for moderate concentrations (C₀~20–30 mg·L⁻¹) and negative for higher C₀ (>30 mg·L⁻¹). Consequently, the US/chlorine process was efficiently operable under typical water treatment conditions, although complete by-product analysis and toxicity assessment may still be necessary to establish process viability.

Hybrid advanced oxidation processes employed to degrade recalcitrant organic pollutants in water have been widely examined in recent years. In the present work, the potential of TiO₂-mediated photocatalysis in the presence of the periodate anion (IO₄⁻) toward Safranin O (SO) removal from aqueous solutions was investigated. The findings revealed a high efficiency of the UV/TiO₂/IO₄⁻ system due to the production of more reactive radicals (^•OH, IO₃^• and IO₄^•) and non-radical species (O₃, IO₃⁻ and IO₄⁻). Additionally, the presence of IO₄⁻ as an effective electron acceptor avoids electron-hole recombination, which induces more oxidative reactions at the hole level, increasing the degradation rate of SO. Kinetically, the involvement of IO₄⁻ anions in the UV/TiO₂ system enhanced substantially the initial rate of degradation; from 0.295 to 12.07 mg L⁻¹ min⁻¹. The performance of both systems, i.e., UV/TiO₂ and UV/TiO₂/IO₄⁻, was examined under different conditions such as initial dye concentration, photocatalyst loading, periodate dosage, initial solution pH, temperature and dissolved gases. The SO degradation was found to be maximized at low concentration of pollutant at the optimum loading of catalyst (0.4 g L⁻¹). The continuous increasing in periodate concentration over the range of 0.01–3 mM improved the system reactivity with no overdose effect. Both systems seemed to be insensitive to minor variations in temperature in the range of 15–45 °C, and showed a strong dependence on initial solution pH where the degradation rates increased proportionally with pH values up to pH 10 and decreased afterwards. A slight negative effect on the photocatalytic removal yield was noted under either aeration, nitrogen or argon atmospheres in the presence of periodate (UV/TiO₂/IO₄⁻), with minor enhancement under aeration for the classical system (UV/TiO₂). The mineralization of the organic substrate was also monitored. The depletion of organic matter with time was measured using total organic carbon (TOC) analysis. Despite the rapid decolorization of the dye solution in the UV/TiO₂/IO₄⁻ system, a TOC removal efficiency of ~62% was obtained with both systems after 180 min of treatment.

In addition to bubble number density, bubble size distribution is an important population parameter governing the activity of acoustic cavitation bubbles. In the present paper, an iterative numerical method for equilibrium size distribution is proposed and combined to a model for bubble counting, in order to approach the number density within a population of acoustic cavitation bubbles of inhomogeneous sizing, hence the sonochemical activity of the inhomogeneous population based on discretization into homogenous groups. The composition of the inhomogeneous population is analyzed based on cavitation dynamics and shape stability at 300 kHz and 0.761 W/cm² within the ambient radii interval ranging from 1 to 5 µm. Unstable oscillation is observed starting from a radius of 2.5 µm. Results are presented in terms of number probability, number density, and volume probability within the population of acoustic cavitation bubbles. The most probable group having an equilibrium radius of 3 µm demonstrated a probability in terms of number density of 27%. In terms of contribution to the void, the sub-population of 4 µm plays a major role with a fraction of 24%. Comparisons are also performed with the homogenous population case both in terms of number density of bubbles and sonochemical production of ${\mathrm{HO}}^{•},{\mathrm{HO}}_2{}^{•},$ and ${\mathrm{H}}^{•}$ under an oxygen atmosphere.

The present paper investigates the potential of the Galvano-Fenton process as an advanced technique in terms of the simultaneous oxidation of a model pollutant, phenol, and the energy release and saving as compared to conventional electrochemical techniques, namely, Fenton, Fenton-like, and Electro-Fenton. A numerical model describing the electrochemical, electrolytic, and phenol’s mineralization reactions is presented. Simulations are conducted to predict the kinetics of ferrous and ferric ions, radicals’ formation, and phenol degradation along with released power. Parametric analysis and comparisons are also performed between the basic configuration of the Galvano-Fenton process and its upgraded version integrating a pre-immersion stage of the electrodes in the electrolyte equivalent to 25% of the total experiment’s duration. The ratio of the initial concentration of $H_2{O}_2$ to the concentration of the released/added $F{e}^{2+}$ catalyst is varied from 10 to 30. The effect of phenol concentration is inspected over the range of 0.188 to 10 mg/L as well. Compared to conventional Fenton-based techniques, the Galvano-Fenton process demonstrated a higher performance by reaching 1.34% of degradation efficiency per released J. This is associated with the generation of hydroxyl radicals of 0.047 nM/released J with initial concentrations of hydrogen peroxide and phenol of 0.187 mM and 2 µM, respectively. Moreover, the integration of the pre-immersion stage allowed the overcoming the barrier of the null degradation rate at the initial instant.