Obtention of biochar-Fe/Ce using Punica granatum with high adsorption of ampicillin capacity.

This research presents the obtaining of a biochar (CB) from the use of pomegranate peel (Punica granatum) conditioned with iron and cerium nanoparticles (C-Fe/Ce), as well as its characterization by SEM (Scanning Electronic Microscopy), FTIR (Fourier Transform Infrared Spectrometry), TGA (Thermogravimetric analysis), EDS (Energy Dispersive Spectroscopy), XPS (X-Ray Photoelectron Spectroscopy) and evaluation of the adsorption capacity of ampicillin (AMP) in aqueous phase at 20, 30 and 40 °C. The maximum adsorption capacity for CB was 18.97 mg g-1 and for C-Fe/Ce, 27.61 mg g-1 at pH of 7, observing that with increasing temperature, the sorption capacity decreases in both materials, the experimental data was fitted to various mathematical models and the best fit was the pseudo-second order model for the kinetics, whilst for the adsorption isotherms the best fit was with the Langmuir model, indicating that the adsorption process is carried out in a monolayer on a homogeneous surface, through a chemisorption process. According to the thermodynamic parameters this process is carried out through an exothermic reaction. The results obtained indicate that both materials are suitable for the removal of AMP in the aqueous phase and that they can be reused up to 5 times.

Obtention of biochar-Ca nanoparticles using Citrus tangerina׃ A morphological, surface and study remotion of Aflatoxin AFB1.

This work presents the formation of biochar with calcium nanoparticles (NPsCa) in function of pyrolysis time (C10, C30, C60, C120 and C180 min) using the Citrus tangerina peel and their evaluation in the remotion of Aflatoxin B1 (AFB1) in aqueous phase. Firstly, the Citrus tangerina was studied by Thermogravimetric analysis to determine the optimal temperature (TGA), obtaining a result of 600 °C. The biochar (NPsCa) were characterized by Scanning Electronic Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), as well as surface properties including the identification of functional groups by Fourier Transform Infrared Spectrometry (FTIR), and energetic states through the X-Ray Photoelectron Spectroscopy (XPS). The adsorption studies were carried out on the different materials and later, the experimental data was adjusted to different mathematical models, obtaining the best fit of the kinetic data to the Ho-McKay model, whilst the adsorption isotherms were adjusted to the model of Langmuir, which indicates that the Aflatoxin B1 adsorption process is carried out through a monolayer chemisorption process with maximum sorption capacities (qm) ranging between 15.72 and 63.22 µg g-1 with the 180th minute being the adequate time to obtain the carbon with the best surface properties and the best adsorption capacity. Additionally, it was observed that each material can be reused up to five times in accordance with the results from the reuse cycles.

Synthesis, characterization and adsorptive properties of carbon with iron nanoparticles and iron carbide for the removal of As(V) from water.

This manuscript presents the synthesis of carbon modified with iron nanoparticles (CFe) and iron carbide (CarFe) from the pyrolyzed crown leaves of pineapple (Ananas comosus) treated with iron salts. The materials that were obtained were used for the removal of As(V) from aqueous media. The carbonaceous materials were characterized by Scanning Electron Microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS) and Mossbauer Spectroscopy. The specific area (BET), number site density and point of zero charge (pH(pzc)) were also determined. The kinetic parameters were obtained by fitting the experimental data to the pseudo-first-order and pseudo-second-order models. Different isotherm models were applied to describe the As(V) adsorption behavior. The kinetics of As(V) sorption by CFe and CarFe was well defined for the pseudo-second-order model (R(2) = 0.9994 and 0.999, respectively). The maximum As(V) uptake was 1.8 mg g(-1) for CFe and 1.4 mg g(-1) for CarFe. The results obtained indicated that both materials are equally useful for As(V) sorption. The As(V) experimental isotherm data were described by the Freundlich model for CFe and CarFe.

Effect of the pH and temperature on the biosorption of lead(II) and cadmium(II) by sodium-modified stalk sponge of Zea mays.

OBJECTIVE: The present work was carried out to investigate the effects of temperature, initial pH, initial concentration, and contact time on the biosorption of lead (Pb) and cadmium (Cd) by modified stalk sponge of Zea mays using a batch technique. METHODS: The biomass was chemically modified with a 0.1 M NaCl solution. The lead and cadmium sorption process was evaluated at 20°C, 30°C, 40°C, and 50°C. RESULTS: The results showed that the modified stalk sponge of Z. mays had a good capacity for biosorption of Pb(II) and Cd(II). The kinetic behavior was described by the pseudo-second-order model for both metallic species. The experimental isotherms obtained at different temperatures were fit with Langmuir and Freundlich models. Thermodynamic parameters ΔH(0) and ΔS(0) were calculated using the van't Hoff equation, and the results show that Pb(II) and Cd(II) sorption by modified stalk sponge of Z. mays is an exothermic and spontaneous process.

Biosorption of lead by maize (Zea mays) stalk sponge.

This study investigated the removal of Pb(II) from aqueous solutions by a maize (Zea mays) stalk sponge. Equilibrium and kinetic models for Pb(II) sorption were developed by considering the effect of the contact time and concentration at the optimum pH of 6 +/- 0.2. The Freundlich model was found to describe the sorption energetics of Pb(II) by Z. mays stalk sponge, and a maximum Pb(II) loading capacity of 80 mg g(-1) was determined. The kinetic parameters were obtained by fitting data from experiments measuring the effect of contact time on adsorption capacity into pseudo-first and second-order equations. The kinetics of Pb(II) sorption onto Z. mays biosorbent were well defined using linearity coefficients (R(2)) by the pseudo-second-order equation (0.9998). The results obtained showed that Zea may stalk sponge was a useful biomaterial for Pb(II) sorption and that pH has an important effect on metal biosorption capacity.

Interaction between U(VI) and SrTiO3 surfaces versus temperature.

The purpose of this work is the study of the interaction mechanisms between U(VI) ions and SrTiO(3) surfaces as a function of pH and temperature (25, 50, 75 and 90 degrees C) by coupling thermodynamic and spectroscopic approaches. First, the reactivity towards U(VI) for both surface sites of the strontium titanate ([triple bond]Ti-O and [triple bond]Sr-O) has been investigated as a function of the temperature. The N(2)-BET specific area was measured: 2.4+/-0.2 m(2)g(-1). The surface site density has been determined from potentiometric titrations (6 sites/nm(2) for each site [triple bond]Ti-O and [triple bond]Sr-O). The potentiometric titration data have been simulated, for each temperature, using the FITEQL 4.0 software and the constant capacitance model, taking into account both protonation of the [triple bond]Sr-OH surface sites and deprotonation of the [triple bond]Ti-OH ones (one pK model). The intrinsic strontium protonation constant increases with an increasing temperature, while the titanate deprotonation one decreases. Moreover, both enthalpy and entropy changes corresponding to the surface acid-base reactions have been evaluated using the van't Hoff relation. The uranium(VI) ions are sorbed onto SrTiO(3) surfaces in the 0.5-5.0 pH range with an initial cation concentration equal to 10(-4) M. The U(VI) surface complexes were identified by using time-resolved laser-induced fluorescence spectroscopy (TRLFS). For all the studied samples, the fluorescence spectra and the corresponding lifetime values do not change with the pH and the temperature. Two U(VI) complexes sorbed onto SrTiO(3) were detected and the corresponding lifetimes are 60+/-5 and 12+/-2 micros whatever the temperature (25, 50, 75 and 90 degrees C). The sorption edges were simulated with the FITEQL 4.0 code. The sorption equilibrium constants of the U(VI)/SrTiO(3) system between 25 and 90 degrees C were obtained with the constant capacitance model (CCM), considering two reactive surface sites. According to the spectroscopic characterization, two types of surface complexes, namely [([triple bond]SrOH)([triple bond]TiOH)UO(2)](2+) and [([triple bond]TiOH)([triple bond]TiO)UO(2)](2+), were considered. Finally, enthalpy (Delta(r)H(o)) and entropy (Delta(r)S(o)) changes were calculated from the temperature-dependent sorption constants, by the application of the van't Hoff formalism. The formation of the [([triple bond]SrOH)([triple bond]TiOH)UO(2)](2+) surface complex was found to present an endothermic character associated to an increase in the disorder of the system. On the contrary, the formation of the [([triple bond]TiOH)([triple bond]TiO)UO(2)](2+) surface complex led to an exothermic process with only a slight increase in the disorder of the system.