Hydrothermal Carbon Coating of an Activated Carbon-A New Adsorbent.

A new adsorbent material was prepared by coating an activated carbon with hydrothermal carbon obtained from sucrose. The material obtained has different properties from the sum of the properties of the activated carbon and the hydrothermal carbon, which shows that a new material was obtained. It has a high specific surface area (1051.9 m2 g-1) and is slightly more acidic than the starting activated carbon (p.z.c.-point of zero charge 8.71 vs. 9.09). The adsorptive properties of a commercial carbon (Norit RX-3 Extra) were improved over a wide pH and temperature range. The capacity values of the monolayer according to Langmuir's model reached 588 mg g-1 for the commercial product and 769 mg g-1 for the new adsorbent.

Olive-tree polyphenols and urban mining. A greener alternative for the recovery of valuable metals from scrap printed circuit boards.

Recycling printed circuit boards (PCBs) is becoming a source of precious metals and an alternative to conventional mining. This phenomenon is now known as "urban mining." In this work, a polyphenols-rich plant extract has been obtained from olive-tree leaves, and its ability to contribute to reducing four metals, namely, Ag, Cu, Cr, and Sn, that are present in scrap PCBs has been studied. Three reductants (NaBH4, Fe°, and the olive-tree leaves extract) have been used to recover these valuable metals. An attempt has been made to minimize the concentration of the first two, replacing them with a natural, cheaper, and less toxic reductant. To achieve this goal, a computer-assisted factorial, composed, centered, orthogonal, and rotatable statistical design of experiments (FCCORD) has been used to build the experimental matrix to be carried out in the laboratory and, next, for the statistical treatment of the results. The results show that it is possible to achieve only a partial recovery of the four metals (silver, copper, chromium, and tin) from PCBs leachates by using sodium borohydride, iron, and the extract separately. In other words, none of these three reductants alone can completely remove any of the four metals in the leachate. Nevertheless, using the statistical design of experiments, the total recovery of the four metals has been achieved by combining the three reductants in the appropriate concentrations. Hence, polyphenols-rich plant extracts in general and olive-tree leaves extract in particular can be regarded as promising coadjuvants in the rising field of urban mining.

Preparation of high-quality activated carbon from polyethyleneterephthalate (PET) bottle waste. Its use in the removal of pollutants in aqueous solution.

A waste-treats-waste approach has been used for the removal of two common pollutants, namely p-nitrophenol and/or Fe(III) from aqueous solution. Polyethyleneterephthalate (PET) from bottle waste has been used as the precursor for the preparation of activated carbons (ACs) by physical activation with steam and chemical activation with potassium hydroxide under controlled heating conditions and atmospheres. The resulting ACs were characterized in terms of chemical composition, porous texture and surface chemistry, and morphology. Selected ACs were tested as adsorbents for the removal of the aforementioned pollutants in aqueous solution. For comparison purposes, a commercial AC was also used. In general, the yield of the process of preparation of ACs is lower than 10% with steam and between 24.62 and 32.07% with potassium hydroxide. ACs possess a very high carbon content and a very low ash content. The BET surface areas reach 1235 m(2) g(-1) with steam and 1002 m(2) g(-1) with potassium hydroxide at most. Also, the degrees of development of micro- and mesoporosity are markedly larger with steam. Conversely, the development of macroporosity is much larger with potassium hydroxide. The PET-derived ACs exhibit a better adsorption behavior towards p-nitrophenol than the commercial AC, both in terms of adsorption rate and adsorption capacity. On the contrary, the commercial AC acts as a better adsorbent of Fe(III) ions. As compared to separately, the simultaneous presence of both solutes in the adsorptive solution scarcely affects the adsorption process except for equilibrium for Fe(III).

Single adsorption of diclofenac and ronidazole from aqueous solution on commercial activated carbons: effect of chemical and textural properties.

The importance of the textural and physicochemical characteristics upon the adsorption capacity of the commercial activated carbons (ACs) Coconut, Wood, Merck, Darco, and Norit towards ronidazole (RNZ) and diclofenac (DCF) from water solution was investigated thoroughly in this work. At pH = 7, Coconut AC and Wood AC presented the highest adsorption capacity towards RNZ (444 mg/g) and DCF (405 mg/g). The maximum mass of RNZ adsorbed onto Coconut AC was higher in this study than those outlined previously in other works. Besides, the maximum capacity of Wood AC for adsorbing DCF was comparable to those found for other ACs. The adsorption capacity of all the ACs was increased by surface area and was favored by incrementing the acidic site concentration. The π-π stacking interactions were the predominant adsorption mechanism for the RNZ and DCF adsorption on ACs, and the acidic sites favored the adsorption capacity by activating the π-π stacking. Electrostatic interactions did not influence the adsorption of RNZ on Coconut AC, but electrostatic repulsion decreased that of DCF on Wood AC. The adsorption of DCF on Wood AC was reversible but not that of RNZ on Coconut AC. Besides, the adsorption of RNZ and DCF on the Coconut and Wood ACs was endothermic in the range of 15-25 °C.

Adsorption of cadmium on carbonaceous adsorbents developed from used tire rubber.

Carbonaceous adsorbents (CAs) are developed from used tire rubber (UTR) and tested as adsorbents of Cd(2+) in aqueous solution. In the preparation of the CAs, UTR was treated thermally at 400-900 °C for 2 h in N(2) and at 850 °C for 2 h in steam. Concentrated NaOH, HCl, H(2)SO(4), HNO(3) and H(2)O(2) solutions were also used. UTR and H900 (i.e. UTR pyrolyzed at 900 °C) were treated with O(3) at 25 °C for 1 h and with air at 250 °C for 1 and 24 h. CAs were characterized texturally by N(2) adsorption at -196 °C, mercury porosimetry, and density measurements. The surface groups were analyzed by FT-IR spectroscopy. Using the batch method, the adsorption process of Cd(2+) was studied mainly from the kinetic standpoint at various pH values of the adsorptive solution. Significant porosity developments are achieved only when UTR is heat-treated, in particular in steam. However, the variety and concentration of surface groups are low in CAs. This is so even for CAs prepared using oxidizing agents as strong as O(3) and H(2)O(2), which has been associated with a lack of available or accessible surface active sites for oxidation in UTR and H900, respectively. Thermal and thermal-chemical treatments are usually more effective than chemical treatments to increase the adsorption of Cd(2+) in aqueous solution. The adsorption process of Cd(2+) is first fast and then much slower. Adsorption-time data fit better to a pseudo-second order kinetic equation than to a pseudo-first order kinetic equation. The extent to which the adsorption process occurs is strongly dependent on the pH of the Cd(2+) solution, being larger at pH 4.6 or 7.0 according to the adsorbent.

Adsorption of bisphenol A by activated carbon developed from PET waste by KOH activation.

This study deals with the preparation of activated carbon (AC) from poly(ethylene terephthalate) (PET) waste and with the physicochemical characterization of AC and its use as adsorbent of bisphenol A (BPA) in aqueous solution. AC was prepared by chemical activation with KOH and by physical activation in steam. The activation with KOH was carried out by impregnation first of PET by wet and dry routes at the PET/KOH weight ratios of 1:1, 1:3, and 1:5 and by carbonization then of the resulting products at 850 °C for 2 h in N2 atmosphere. The activation in steam was performed by heating at 900 °C for 1 h. The ACs were characterized by N2 adsorption at - 196 °C, mercury porosity, mercury density measurements, FT-IR spectroscopy, and measurement of pH of the point of zero charge (pHpzc). The activation yield is 58.4-49.4% with KOH in aqueous solution, 75.8-23.9% with solid KOH, and 5.9% with steam. Using solid KOH, greater developments of a more heterogeneous porosity with increasing impregnation PET/KOH ratio are achieved. For SK1:5, SBET is 1990 m2 g-1 and the pore volumes are 0.71 cm3 g-1, micropores; 0.81 cm3 g-1, mesopores; and 1.77 cm3 g-1, macropores. The data of BPA adsorption fit better to the Ho and Mckay second order kinetic model than to the Lagergren first-order kinetic model and to the Langmuir equation than to the Freundlich equation. From the kinetic and thermodynamic standpoints, the adsorption process of BPA is more favorable for SK1:5.

Cardiac sympathetic denervation in symptomatic and asymptomatic carriers of the E46K mutation in the α synuclein gene.

OBJECTIVE: The aim of this study was to analyze autonomic function and cardiac sympathetic innervation in symptomatic and asymptomatic carriers of the E46K alpha-synuclein gene (SNCA) mutation. PATIENTS AND METHODS: Autonomic function tests were performed in six patients, four of whom were symptomatic carriers (ages: 46, 59, 52 and 28-years) and two who were asymptomatic carriers (ages: 52 and 29 years). Autopsy studies were performed on an additional two symptomatic carriers not eligible for autonomic testing. Patients completed the SCOPA autonomic questionnaire, and underwent the head-up tilt test accompanied by measurements of plasma norepinephrine. Valsalva maneuver and deep breathing tests, along with recording of sympathetic skin response (SSR) and cardiac MIBG scintigraphy were carried out. Myocardial tissue sections removed from the two autopsied cases were subjected to routine histological staining and immunohistochemical processing with monoclonal antibodies against tyrosine hydroxylase and alpha-synuclein. RESULTS: Both the four symptomatic and the older asymptomatic carriers reported abnormalities in the SCOPA questionnaire and had markedly diminished cardiac MIBG uptake. Plasma norepinephrine in the supine and tilted positions was normal in all subjects. Only one patient had significant orthostatic hypotension. There was a complete absence of tyrosine hydroxylase immunostaining in the myocardium of the two autopsied cases. INTERPRETATION: We have found imaging and histological evidence of cardiac sympathetic denervation in symptomatic and asymptomatic carriers of the E46K alpha-synuclein gene mutation. The sympathetic denervation appears to be organ-specific, with selective affectation of the heart given that plasma norepinephrine levels and blood pressure were normal.

On the use of a natural peat for the removal of Cr(VI) from aqueous solutions.

A natural peat has been used as an adsorbent for the removal of hexavalent chromium from aqueous solution. The peat was firstly characterized in terms of particle size and chemical composition (ash content, pH of the point of zero charge, FT-IR and thermal analysis). Next, the kinetic and equilibrium aspects of the adsorption of Cr(VI) by this adsorbent were studied. The kinetic data were satisfactorily fitted to a kinetic law of partial order in C equal to one. The specific adsorption rates are around 10(-4)s(-1), increasing as temperature does. A noticeable influence of diffusion on the global adsorption process has been demonstrated. Finally, the equilibrium isotherms were satisfactorily fitted to a previously proposed model. The adsorption capacity of Cr(VI) was similar to some other previously reported and the affinity of Cr(VI) towards the active sites of the adsorbent increases as temperature rises.