Magnetic biochars were prepared using Fe 3 O 4 nanoparticle composites onto the surface of biochar derived from rice husk. The characteristics of magnetic biochar were characterized by scanning electron microscope, x-ray powder diffraction and Fourier-transform infrared techniques. The removal of rhodamine 6G dye by magnetic biochar, compared to pristine biochar was studied. The effects of pyrolysis temperature on rhodamine 6G adsorption was evaluated. Kinetic, isotherms and thermodynamic studies were carried out to investigate the adsorption mechanism of rhodamine 6G dye on magnetic biochar surface. The rhodamine 6G removal efficiency of Fe 3 O 4 -composited biochar (pyrolyzed at 500°C) is higher than that of pristine biochar with maximum efficiency of 94% removal. The adsorption isotherm and kinetic studies indicated that the langmuir model, pseudo-first order and pseudo-second order models described well the rhodamine adsorption onto magnetic Fe 3 O 4 -biochar. Abbreviations BCBiochar C 0 Initial dye concentration (mg/L) C e Equilibrium concentration of dye (mg/L) ΔG 0 The Gibbs free energy) and f ΔH 0 The change of enthalpy MB Magnetic biochar q e Adsorbed dye amount per gram of sorbent at equilibrium (mg/g) q e,cal Calculated amount of dye adsorbed per gram of adsorbent at equilibrium (mg/g) q e,exp Experimental amount of dye adsorbed per gram of adsorbent at equilibrium (mg/g) q t Adsorbed dye amount per gram of adsorbent at time t (mg/g) K Thermodynamic equilibrium constant K L Langmuir isotherm equilibrium constant representing the energy of sorption (L/mg) K F Freundlich constant representing sorption capacity ((mg/g)(L/mg)/n) k 1 Pseudo-first order rate constant (1/min) k 2 Pseudo-second order rate constant (g/mg·min) n Freundlich isotherm constant representing sorption intensity R The ideal gas constant (8.314 J mol −1 ·K −1 )

Chemical reactivity is profoundly affected by solvent properties. Room temperature ionic liquids (RTILs) obtain molecular environments that differ vastly from those established using molecular solvents with comparable macroscopic properties. In particular, charges are expected to be completely shielded in RTILs even though their dielectric constants are typically low. This raises the question whether electron transfer (ET) reactions in RTILs can be described in terms of Marcus' theory, a model that is fundamentally based on continuum dielectric theory. Herein, we elucidate this question by studying a degenerate electron transfer process, which by design, is not affected by ambiguities in the driving force of the reaction and thus allows a clear-cut assessment of the ET activation energy. We report the rate constants and the activation parameters of the electron self-exchange reaction in the TCNE/TCNE˙(-) couple in seven ionic liquids. The exchange rate constants range from 5.4 × 10(7) M(-1) s(-1) to 9.1 × 10(8) M(-1) s(-1) at 330 K and the activation energies vary from 14 kJ mol(-1) to 41 kJ mol(-1). The results are discussed in the framework of Marcus' theory. It is found that the solvent dependence of the rate constants cannot be described by the classical proportionality to the Pekar factor γ = (1/n(2) - 1/εs).

The large structural difference between thianthrene radical cations and their neutral parent molecules can possibly affect their electron self-exchange reactions. Before this can be investigated experimentally, it is necessary to first understand the influence of the solvent on such electron transfer reactions. To achieve this, the rate constants of the electron self-exchange reactions of the Th˙(+)/Th and MTh˙(+)/MTh (Th = thianthrene, MTh = 2,3,7,8-tetramethoxythianthrene) couples were investigated by means of ESR line broadening experiments in different solvents at 293 K. The diffusion corrected rate constants cover a range of 7.2 × 10(8)≤ket≤ 44 × 10(8) M(-1) s(-1) for Th˙(+)/Th and 2.0 × 10(8)≤ket≤ 11.6 × 10(8) M(-1) s(-1) for MTh˙(+)/MTh, respectively. The results were analysed within the framework of the Marcus Theory and the characteristic reorganization energy, λ, was determined. Both couples clearly show a solvent dynamic effect controlled by the longitudinal relaxation time τL of the solvents. However, the influence of the structural changes, in terms of λ, was smaller than expected at room temperature.

In recent years, the contamination of the aquatic environment with antibiotics, including tetracyclines, has drawn much attention. Bottom ash (BA), a residue from the biomass power plant, was used to synthesize the magnetic mesoporous silica (MMS) and was utilized as an adsorbent for tetracycline (TC) removal from aqueous solutions. The MMS was characterized by Fourier transform-infrared (FTIR), X-ray diffraction (XRD) pattern, and scanning electron microscopy (SEM). Optimum conditions were obtained in overnight incubation at 60 °C, a pH of 6–8, and an adsorption capacity of 276.74 mg/g. The isotherm and kinetic equations pointed to a Langmuir isotherm model and pseudo-first-order kinetic optimum fitting models. Based on the very low values of entropy changes (ΔS°), the negative value of enthalpy changes (ΔH°) (−15.94 kJ/mol), and the negative Gibbs free-energy changes (ΔG°), the adsorption process was physisorption and spontaneous.

Physico-chemical properties and the environmental impacts were studied relative to the leaching of rubber fly ash and bottom ash. The pozzolanic properties of fly ash and bottom ash were confirmed by the chemical composition, including silicon oxides, calcium oxides, and aluminum oxides. The geo-technical characteristics of rubber wood fly ash and bottom ash, i.e., modified compaction, plasticity, and the soaked California Bearing Ratio, were evaluated to assess the feasibility of fly ash or bottom ash mixed with lateritic soil as aggregate materials for the subbase in road construction in order to optimize the replacement of lateritic soil by fly ash or bottom ash. The leachates from rubber fly ash and bottom ash did not exceed standard thresholds. The measured characteristics of fly ash or bottom ash mixed with lateritic soil were in good alignment with the effective engineering thresholds. Recommendations were developed for safe reuse of byproducts from rubber renewable power plant in subbase road construction.