Combined coagulation-electrocoagulation process using biocoagulant from the Opuntia ficus-indica for treatment of cheese whey wastewater.

This work reports a combined coagulation-electrocoagulation process using a biocoagulant from the Opuntia ficus-indica for treatment of cheese whey wastewater. The process parameters as pH, biocoagulant dosage, and current density were evaluated from the chemometric tools. A Box-Behnken design was used, having as responses the removal percentages of turbidity and chemical oxygen demand (COD). The results showed that for the studied variable ranges, linear models were obtained and the pH was parameter more significant for treatment proposed. The pH showed synergic effect with the investigated parameters, while the biocoagulant dosage and density current showed antagonistic effects. The desirability function was used to optimization of process, and suggested values were pH 10.0, biocoagulant dosage of 4.4 g L-1, and current density of 31.5 mA cm-2, which showed removals of turbidity and COD of 98.9 and 83.8%, respectively.

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.

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.

Optimization of Sibipiruna activated carbon preparation by simplex-centroid mixture design for simultaneous adsorption of rhodamine B and metformin.

The present paper reports the application of augmented simplex-centroid mixture design to obtain a high BET surface area activated carbon using as reactants KOH, K2CO3 and K2C2O4. The optimum mixture composition was 2.51 g of KOH, 0.49 g of K2CO3 and absence of K2C2O4, generating an optimized AC (ACop) with SBET value equals to 1984 m2 g-1. The results herein obtained show that low amounts of K2CO3 can catalyze the pore development in the presence of KOH, increasing the surface area. Furthermore, the fractal dimensions of ACop are greater than 2.72, indicating the material has a complex pore structure with irregularities self-similar upon variations of resolution, as seen by SEM images. The TPD curves showed that the ACop has different oxygenated molecular fragments, which agrees with the pHPZC value (5.05). The ACop was applied in the adsorption of rhodamine B (RhB) and metformin (Met) in both binary and monocomponent systems. The simultaneous adsorption at 30 °C reveals that the adsorption capacity of RhB is 630.94 mg g-1, while for Met the value is 103.83 mg g-1.

Removal of Cu(II) from aqueous solutions imparted by a pectin-based film: Cytocompatibility, antimicrobial, kinetic, and equilibrium studies.

To obtain pectin-based films is challenging due to the aqueous instability of polyelectrolyte mixtures. We overcome this issue by blending chitosan to pectin of high O-methoxylation degree (56%), followed by solvent evaporation. A durable film containing 74 wt% pectin content was produced and used as an adsorbent material toward Cu(II) ions. Kinetic and adsorption equilibrium studies showed that the pseudo-second-order and Sips isotherm models adjusted well to the experimental data, respectively. Langmuir isotherm indicated a maximum adsorption capacity (qm) for Cu(II) removal of 29.20 mg g-1. Differential scanning calorimetry, contact angle measurements, and X-ray photoelectron spectroscopy confirm the adsorption. The chemisorption plays an essential role in the process; thereby, the film reusability is low. After adsorption, the cytocompatible film/Cu(II) pair prevents the proliferation of Escherichia coli.

Polysaccharide-based adsorbents prepared in ionic liquid with high performance for removing Pb(II) from aqueous systems.

Alginate/chitosan (ALG/CHT) and alginate/N,N-dimethyl chitosan (ALG/DMC) polyelectrolyte complex (PEC)-based adsorbents with high capacities for removing Pb(II) from aqueous systems are produced in [1-hydrogen-3-methylimidazolium hydrogen sulfate ionic liquid ([Hmim][HSO4-]). The [Hmim][HSO4-] is recovered, characterized by 1H NMR and reused to yield novel polysaccharide-based adsorbents. As-obtained PEC materials are characterized through infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and Zeta potential measurements. Kinetic and equilibrium adsorption studies reveal that the pseudo-second-order Kinetic, as well as the Redlich-Peterson isotherm, provide the best fits for the experimental data, respectively. CHT/ALG and DMC/ALG adsorbents promoted maximum adsorption capacities (qm) of 529.4 mg g-1 and 560.2 mg g-1, respectively. After adsorption, the materials are characterized by infrared spectroscopy and X-ray photoelectron spectroscopy, confirming that the chemisorption prevails upon Pb(II) removal. Also, PECs produced in the recovered [Hmim][HSO4-] have good capacities for removing Pb(II) ions from aqueous systems as well. This study showed that the [Hmim][HSO4-] is an alternative solvent to prepare novel and eco-friendly PEC-based adsorbents.

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.

Mesoporous Graphitic Carbon Nitrides Decorated with Cu Nanoparticles: Efficient Photocatalysts for Degradation of Tartrazine Yellow Dye.

A series of mesoporous graphitic carbon nitride (mpg-C3N4) materials are synthesized by directly pyrolyzing melamine containing many embedded silica nanoparticles templates, and then etching the silica templates from the carbonized products. The mass ratio of melamine-to-silica templates and the size of the silica nanoparticles are found to dictate whether or not mpg-C3N4 with large surface area and high porosity form. The surfaces of the mpg-C3N4 materials are then decorated with copper (Cu) nanoparticles, resulting in Cu-decorated mpg-C3N4 composite materials that show excellent photocatalytic activity for degradation of tartrazine yellow dye. The materials' excellent photocatalytic performance is attributed to their high surface area and the synergistic effects created in them by mpg-C3N4 and Cu nanoparticles, including the Cu nanoparticles' greater ability to separate photogenerated charge carriers from mpg-C3N4.