Consideration of biological and inorganic additives in upgraded anaerobic digestion BioModel.

This paper deals with the numerical simulation of biogas production in the anaerobic digestion process of organic waste. Special attention is focused on the modeling of the activities of biological and inorganic additives, which are used to enhance the process and reduce H2S content in the biogas. For this purpose, an existing BioModel is upgraded with the modified Michaelis-Menten kinetics in order to model the enzymatic hydrolysis and with adequate modeling of physicochemical processes. The upgraded BioModel was calibrated with experimental data obtained from a full-scale biogas plant, used in combination with an active set optimization procedure; the relative agreement indices were 0.9376, 0.9419, 0.7957, and 0.7663 for biogas, CH4, H2, and H2S flow rates, respectively. Statistical efficiency criteria differ up to 5% in model calibration and validation. The obtained results confirm the importance of additives modeling and the usefulness of the proposed model for industrial biogas plants' performance improvement.

Adsorption of rare earth metals from wastewater by nanomaterials: A review.

Rare earth elements are widely used in chemical engineering, the nuclear industry, metallurgy, medicine, electronics, and computer technology because of their unique properties. To fulfil ever increasing demands for these elements, recycling of rare-earth-element-containing products as well as their recovery from wastewater is quite important. In order to recover rare earth elements from wastewater, their adsorption from low-concentration aqueous solutions, by using nanomaterials, is investigated due to technological simplicity and high efficiency. This paper is a review of the state-of-the-art adsorption technologies of rare earth elements from diluted aqueous solutions by using various nanomaterials. Furthermore, desorption and reusability of rare earth metals and nanomaterials are discussed. On the basis of this review it can be concluded that laboratory testing indicates promising adsorption capacities, which depend significantly on nanomaterial type and adsorption conditions. The adsorption process, which mostly follows the Langmuir, Freundlich, Sips, and Temkin isotherms, is typically endothermic and spontaneous. Furthermore, pseudo-second order, pseudo-first order, and intra-particle diffusion models are the best models to describe the kinetics of adsorption. The dominant adsorption mechanisms are surface complexation and ion exchange. More investigation, however, will be required in order to synthesize appropriate, environmentally friendly, and efficient nanomaterials for adsorption of rare earth elements from real wastewater.

Synthesis and characterization of novel γ-Fe2O3-NH4OH@SiO2(APTMS) nanoparticles for dysprosium adsorption.

This paper deals with synthesis and characterization of novel γ-Fe2O3-NH4OH@SiO2(APTMS) nanoparticles formed from magnetic γ-Fe2O3 core, stabilized electrostatically in basic media NH4OH, doped with SiO2 shell and functionalized with 3-aminopropyltrimethoxysilane. The gradually synthesized nanoparticles are characterized in order to analyze their structural, morphology, thermogravimetry, surface area and charge, and magnetic properties. The novel synthesized γ-Fe2O3-NH4OH@SiO2(APTMS) nanoparticles are suitable to adsorb dysprosium ions (Dy3+), as one of the most critical rare earth elements, from aqueous solution. The Dy3+ adsorption from aqueous solution follows a pseudo-second order kinetic model and the adsorption equilibrium data fits well to the Temkin isotherm. Thermodynamic studies imply that the adsorption process is endothermic and spontaneous in nature. The maximum adsorption efficiency for Dy3+ from aqueous solution with 2·10-6M concentration of Dy3+ is over 90% at pH 7.

Terbium Ion Adsorption from Aqueous Solution by Using Magnetic γFe2O3-NH4OH@SiO2 Nanoparticles Functionalized with Amino Groups.

New magnetic stabilized and functionalized core@shell nanoparticles (NPs) were synthesized in a simple way and characterized in order to adsorb Tb3+ from aqueous solution with a very low Tb3+ concentration. For the fluorescence determination of adsorption efficiency and capacity, tiron monohydrate as a ligand was used. The obtained results confirm the potential of the synthesized magnetic γ-Fe2O3-NH4OH@SiO2 NPs, functionalized with (3-Aminopropyl) trimethoxysilane (APTMS), to be used for adsorption of Tb3+ from aqueous solution, with the possibility of its removal from aqueous solution via an external magnet. The endothermic and spontaneous adsorption follows a pseudo-second-order kinetic model, and the adsorption equilibrium data fit the Temkin isotherm well. The maximum adsorption efficiency from aqueous solution with a 2 × 10-6 M concentration of Tb3+ is over 90% at pH 7.