No abstract

The potential use of raw and expanded perlite as low-cost adsorbents for biogas purification has been investigated. The thermal expansion of perlite causes a reduction in the density of silanol groups from 2515.43 to 653.75 OH/nm 2 ; in contrast, the specific surface area of perlite increased two-fold due to the thermal expansion. To determine the equilibrium adsorption capacity and the adsorption kinetics batch experiments were conducted. The adsorption capacities are in the following order: activated carbon (6.8 mg/g) > silica gel (6.6 mg/g) > expanded perlite (5.81 mg/g) > raw perlite (5.6 mg/g) when compared at the same experimental conditions. The equilibrium adsorption data showed that perlite can be used to reduce the octamethylcyclotetrasiloxane concentration below 28 mg/m 3 , as recommended by leading manufacturers. The adsorption kinetics of octamethylcyclotetrasiloxane onto raw and expanded perlite followed the Linear-Driving Force model suggesting that the mass transfer is the ratecontrolling step. In addition to its low cost, expanded perlite has the advantage of requiring lower desorption temperature (200 ºC) for regeneration in comparison to the reported values for activated carbon (> 400 ºC) and fast desorption kinetics (20 min), which could contribute to a cleaner production of biogas.

No abstract

No abstract

No abstract

trans-Cinnamic acid was synthesized under microwave irradiation, and it was used for the removal of copper, a toxic metal found in industrial wastewater, from synthetic polluted aqueous solutions. Copper removal is more favorable at pH 5 and was enhanced by increasing the copper initial concentration, reaching a maximum uptake capacity of 389.5 mg/g, which is higher than those reported in the literature. Temperature exhibited a negligible effect on the removal of copper by transcinnamic acid. The isotherm equilibrium uptake data were found to be described by the Langmuir model. In addition, the study of the removal kinetics shows that the uptake of copper by trans-cinnamic acid follows pseudo-first order kinetics, and equilibrium is attained at approximately 30 min. Based on the X-ray photoelectron spectroscopy, X-ray diffraction, scanning transmission electron microscopy, and Fourier-transform infrared spectroscopy studies, a copper−cinnamic acid complex [Cu(CA) 2 ] is formed during the removal process. The reusability of this coordination compound was investigated using HCl, HNO 3 , and NaOH 0.1 M as desorption eluents; HCl was capable of completely desorbing copper from [Cu(CA) 2 ], and transcinnamic acid was recovered as the trans-isomer. Alternatively, the [Cu(CA) 2 ] was used to remove octamethylcyclotetrasiloxane from gaseous streams for biogas purification, obtaining an adsorption capacity of 3.37 mg/g. These promising results demonstrate the feasibility of copper removal by trans-cinnamic acid because of its high uptake capacity and potential reusability.

No abstract

No abstract