Adsorption of model systems of triclosan by mineral sorbent diatomite is studied. The triclosan equilibrium concentration was measured spectrophotometrically, the morphology of the diatomite characterized using scanning electron microscopy and the amount of the adsorbed triclosan on the diatomite quantified by a mass balance. Adsorption isotherms were analyzed according to the linear/nonlinear form of Langmuir, Freundlich, Sips and Toth isotherm models isotherms, using AMPL software. It is shown that nonlinear Langmuir and Sips isotherm model provided suitable fitting results and no pronounced difference in adsorption efficiency between isotherms measured after 1, 2 and 3days adsorption was observed. Determined maximum adsorption capacity of diatomite towards triclosan qs is 140mg/g. Averaged calculated values of ΔG are −9.9 and −9.6kJ/mol for Langmuir and Sips models respectively. The negative sign of such values indicates spontaneous, physical in nature adsorption.

The potential of a bacterial exopolysaccharide named FucoPol, produced by the bacterium Enterobacter A47, as encapsulation matrix was explored. Spherical capsules with a smooth surface were produced by spray drying. The obtained microcapsules had average diameters ranging from 0.5 to 26.7μm and presented thin walls (thickness from 222 to 1094nm). The capsules were loaded with two bioactive compounds: gallic acid (GA) and oregano essential oil (OEO). Both bioactive materials were encapsulated in FucoPol particles, retaining their antioxidant activity after the drying process. Release studies showed that GA release in simulated gastric and intestinal fluids was faster than that of OEO, envisaging that the latter had established stronger interactions with the polymer matrix. These results suggest that FucoPol has a good potential for use as encapsulating material of bioactive compounds for application in several areas, including food, cosmetic or pharmaceutical products.

Oxidized and sulfonated-activated carbons (AC) were tested in the catalytic conversion of glycerol by acetalization reactions. The solids were treated with concentrated nitric acid and/or fuming sulfuric acid (AC, AC-N, AC-S, and AC-NS). The presence of sulfur and an increase in the acidity of the solids demonstrate the suitability of the oxidation as well as the sulfonation process, especially in the sample treated with concentrated nitric acid and fuming sulfuric acid (AC-NS). The best catalyst for the reaction of glycerol acetalization with phenylacetaldehyde was AC-NS, with a phenylacetaldehyde conversion of 95 {%} after 90 min at 383 K and selectivity of 88 and 12 {%}, respectively, to dioxolane and dioxane. These products can be used as hyacinth fragrance flavoring compounds. Furthermore, a contribution of homogeneous catalysis in these systems was not identified. Thus, we identified a possibility of glycerol conversion, a biodiesel by-product, into value-added products by suitable catalysts produced from activated carbons.

In the present study, a novel porous carbon obtained by K2CO3 activation of potato peel waste under optimized conditions was applied for the first time as liquid-phase adsorbent of sodium diclofenac in parallel with a commercial activated carbon. The biomass-activated carbon presented an apparent surface area of 866 m2 g−1 and well-developed microporous structure with a large amount of ultramicropores. The obtained carbon presented leaching and ecotoxicological properties compatible with its safe application to aqueous medium. Kinetic data of laboratory-made and commercial sample were best fitted by the pseudo-second-order model. The commercial carbon presented higher uptake of diclofenac, but the biomass carbon presented the higher adsorption rate which was associated with its higher hydrophilic nature which favoured external mass transfer. Both adsorbents presented adsorption isotherms that were best fitted by Langmuir model. The biomass carbon and the commercial carbon presented adsorption monolayer capacities of 69 and 146 mg g−1, and Langmuir constants of 0.38 and 1.02 L mg−1, respectively. The better performance of the commercial sample was related to its slightly higher micropore volume, but the most remarkable effect was the competition of water molecules in the biomass carbon.

Biodiesel production generates low particle size rapeseed waste (recovered from warehouse air filtration systems) that was herein explored as promising biomass precursor of chemically activated carbons. The influence of several experimental parameters on the porosity development was investigated. No benefit was observed when solution impregnation was made nor a significant dependence of the biomass : K2CO3 ratio was observed and{,} as expected{,} high porosity development was obtained only for treatments at 700 [degree]C. Microporous materials with apparent surface area around 1000 m2 g-1 were obtained comparing favorably with literature data regarding activated carbons from rapeseed processing by-products. A selected lab-made sample and two commercial carbons were tested as adsorbents of caffeine from aqueous solution. Although commercial materials present a quicker adsorption rate{,} regarding adsorption capacity the lab-made sample reaches the same value attained by a benchmark material. The regeneration tests made over the rapeseed derived carbon through heat treatments at 600 [degree]C for 1 hour under N2 flow proved that at least two exhaustion-regeneration cycles can be made since the material retains a caffeine adsorption capacity similar to that of the fresh carbon. Therefore{,} a waste management problem of biodiesel industry - rapeseed residue - can be transformed in a valuable material with promising properties for environmental remediation processes.

Clofibric acid is the metabolite and active principle of blood lipid regulators, it represents the class of acidic pharmaceuticals, and is one of the most persistent drug residues detected in the aquatic environment worldwide. This interdisciplinary work evaluates the effect of solution pH and water hardness in clofibric acid adsorption onto commercial activated carbons. Kinetic and equilibrium assays revealed that the highest clofibric acid removal efficiencies (>70%) were attained at pH 3, and that at pH 8 water hardness degree plays a fundamental role in the adsorption process. In hard water at pH 8 the removal efficiency values increased by 22 or 46% points depending on the carbon sample. Adsorbents’ textural properties also affect the adsorption process since for the microporous sample (CP) the increase of water hardness has a great influence in kinetic and equilibrium data, while for the micro+mesoporous carbon (VP) the variation of the water hardness promoted less significant changes. At pH 3 the increase of water hardness leads to changes in the adsorption mechanism of clofibric acid onto CP carbon signaled by a transition from an S-type to an L-type curve. At pH 8 the change from deionized water to hard water doubles the maximum adsorption capacity of sample CP (101.7mgg−1 vs 211.9mgg−1, respectively). The adsorption enhancement, with water hardness under alkaline conditions, was reasoned in terms of calcium complexation with clofibrate anion exposed by molecular modeling and conductivity studies. Ca2+ complexation by other acidic organic compounds may also occur, and should be considered, since it can play a fundamental role in improved design of water treatment processes employing activated carbons.

The kinetic parameters of the adsorption process at ``liquid–solid'' interface have been evaluated through the sets of time-based experiments of the Cr(III) adsorption under varying temperature, initial metal concentration, and carbon loading for two sets of the commercially available activated carbons and their post-oxidized forms with different texture and surface functionality.

The adsorption of triclosan as model system was studied to qualify activated carbon sorbents recycled from gas masks (civilian gas mask GP5). The triclosan equilibrium concentration was measured spectrophotometrically, the morphology of the activated carbon characterized by scanning electron microscopy, and the amount of the adsorbed triclosan on the activated carbon quantified by a mass balance method. Experimental isotherms were fitted by Langmuir, Freundlich and Sips adsorption models. It was obtained that the contact time is a crucial sorption parameter that provides information on the optimum adsorption efficiency. It was shown that the maximum efficiency of GP5 (88%) is obtained after 10days of adsorption at a maximal concentration of triclosan and carbon loading 1mg/l. No significant adsorption efficiency differences were measured after 5 and 10days of adsorption. The non-linear Sips isotherm, a combined Freundlich–Langmuir model, provides suitable fitting results. The observed remarkable adsorption capacity of activated carbon (GP5) towards triclosan adsorption (∼85mg/g) makes it a viable solution for wastewater treatment.