KOH-super activated carbon from biomass waste: Insights into the paracetamol adsorption mechanism and thermal regeneration cycles.

A super activated carbon (SAC) was produced by KOH-activation of a biomass waste for paracetamol (PCT) adsorption from aqueous solution and for adsorption-thermal regeneration cycles. The SAC and the regenerated SAC after five adsorption-regeneration cycles (RSAC-5th) were fully characterized by several techniques. The N2 physisorption showed that the SBET values of the SAC and RSAC-5th are remarkably different, being 2794 m² g-1 and 889 m² g-1, respectively. The XPS analysis demonstrated that the SAC surface is composed by oxygen containing-groups, whilst the RSAC-5th also presents nitrogen ones, provenient from the PCT molecules. The adsorption studies revealed that the maximum adsorption capacity (Qm) for the SAC (356.22 mg g-1) is higher than that for RSAC-5th (113.69 mg g-1). Also, the results demonstrated that the PCT adsorption is governed by both physisorption and chemisorption and the ab initio calculations showed the chemisorption mainly occurs in carboxylic groups.

Stevia residue as new precursor of CO2-activated carbon: Optimization of preparation condition and adsorption study of triclosan.

The present work reports the preparation of CO2-activated carbon (AC) using Stevia rebaudiana (Bertoni) residue as a new carbon precursor. The experimental parameters were optimized via chemometrics tools to obtain an AC with high BET surface area (SBET). The found optimum condition was: activation temperature of 900 °C, CO2 flow of 165 cm3 g-1 and activation time of 60 min, providing an ACop with SBET of 874 m2 g-1. The ACop was characterized from several analytical techniques, which showed that it has heterogeneous morphology features and different surface chemical groups, predominating the acidic character. The adsorption performance of ACop for triclosan (TCS) removal from solution was investigated by kinetic, equilibrium and thermodynamic studies. The results showed that TCS adsorption process onto ACop is spontaneous and endothermic, wherein the mechanism occurs by different steps, which equally play important roles. Additionally, the monolayer adsorption capacity (Qm) was found to be 117.00 mg g-1.

Inexpensive Bismuth-Film Electrode Supported on Pencil-Lead Graphite for Determination of Pb(II) and Cd(II) Ions by Anodic Stripping Voltammetry.

The present work reports the development and application of bismuth-film electrode (BiFE), obtained by in situ method on the pencil-lead graphite surface, for simultaneous Cd(II) and Pb(II) determination at trace levels, as alternative to replace the mercury-film electrodes. Experimental factors, deposition time (t d ), deposition potential (E d ), and Bi(III) concentration (C Bi ), were investigated by applying a 23 factorial design using 0.10 mol/L acetate buffer solution (pH 4.5) as supporting electrolyte. The analysis conditions of the differential pulse technique were t d = 250 s, E d = -1.40 V, and C Bi = 250 mg L-1. The validation of the method employing BiFE was accomplished by determination of merit figures. The detection limits were of 11.0 µg L-1 for Cd(II) and 11.5 µg L-1 for Pb(II), confirming that proposed method is attractive and suitable for heavy metals determination. Additionally, the BiFE developed was successfully applied for the Cd(II) and Pb(II) determination in wastewater sample of battery industry.

Adsorption of caffeine on mesoporous activated carbon fibers prepared from pineapple plant leaves.

The present work reports the preparation of activated carbon fibers (ACFs) from pineapple plant leaves, and its application on caffeine (CFN) removal from aqueous solution. The preparation procedure was carried out using the H3PO4 as activating agent and slow pyrolysis under N2 atmosphere. The characterization of materials was performed from the N2 adsorption and desorption isotherms, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, Boehm titration and pHpzc method. ACFs showed high BET surface area value (SBET = 1031m2 g-1), well-developed mesoporous structure (mesopore volume of 1.27cm³ g-1) and pores with average diameter (DM) of 5.87nm. Additionally, ACFs showed features of fibrous material with predominance of acid groups on its surface. Adsorption studies indicated that the pseudo-second order kinetic and Langmuir isotherm models were that best fitted to the experimental data. The monolayer adsorption capacity was found to be 155.50mgg-1. thermodynamic studies revealed that adsorption process is spontaneous, exothermic and occurs preferably via physisorption. The pineapple leaves are an efficient precursor for preparation of ACFs, which were successful applied as adsorbent material for removal of caffeine from the aqueous solutions.

Preparation of biosorbents from the Jatoba (Hymenaea courbaril) fruit shell for removal of Pb(II) and Cd(II) from aqueous solution.

In this study, the biosorption properties of Jatoba (Hymenaea courbaril) fruit shell for removal of Pb(II) and Cd(II) ions from aqueous solutions, and its potential as a low-cost biosorbent for water treatment, were investigated. The Jatoba fruit shell (JBin) was subjected to different treatments with heated water (JBH2O) and sodium hydroxide (JBNaOH) to modify its surfaces and improve its adsorption properties. The chemical modification of the surfaces of the resulting materials was confirmed by analyzing the compositions and structural features of the raw material and the chemically treated materials using SEM, FTIR, 13C NMR, and pHpzc. The ability of the biosorbents to remove the metal ions was investigated with batch adsorption procedures. The adsorption data were then examined in detail by applying adsorption models of Langmuir, Freundlich, and Dubinin-Radushkevich. The results showed that the experimental data were best described by the Langmuir model for the Pb-JBin and Cd-JBNaOH systems, the Freundlich model for the Pb-JBH2O and Pb-JBNaOH systems, and the Dubinin-Radushkevich model for Cd-JBin and Cd-JBH2O systems. The maximum adsorption capacities of JBNaOH obtained using the Langmuir model reached values of 30.27 and 48.75 mg g-1 for Cd(II) and Pb(II), respectively. The adsorption kinetic studies showed that the pseudo-second-order model was the best fitted to the experimental data, and adsorptions for Pb-JBH2O and Cd-JBH2O are controlled by intraparticle diffusion mechanism.

Preparation and characterization of activated carbon from a new raw lignocellulosic material: flamboyant (Delonix regia) pods.

Activated carbons were prepared from flamboyant pods by NaOH activation at three different NaOH:char ratios: 1:1 (AC-1), 2:1 (AC-2), and 3:1 (AC-3). The properties of these carbons, including BET surface area, pore volume, pore size distribution, and pore diameter, were characterized from N(2) adsorption isotherms. The activated carbons obtained were essentially microporous and had BET surface area ranging from 303 to 2463 m(2) g(-1).(13)C (CP/MAS and MAS) solid-state NMR shows that the lignocellulosic structures were completely transformed into a polycyclic material after activation process, thermogravimetry shows a high thermal resistance, Boehm titration and Fourier-transform infrared spectroscopy allowed characterizing the presence of functional groups on the surface of activated carbons. Scanning electron microscopy images showed a high pore development. The experimental results indicated the potential use of flamboyant pods as a precursor material in the preparation of activated carbon.