No abstract

No abstract

This work reports the preparation of activated carbons via the hydrothermal treatment at 523 K/30 bar of two common winemaking wastes: bagasse and cluster stalks. The hydrothermal carbons produced by the above treatment were turned into activated carbons via their exposure to KOH and carbonization at 1073 K. These were then subjected to Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy examination, and the determination of their Brunauer-Emmett-Teller surface area. The ability of the activated carbons to adsorb methylene blue in aqueous solution was then examined, determining the influence of time, methylene blue concentration, and temperature. Equilibrium conditions were reached for reaction times between 180 and 240 min at pH 7. The adsorption isotherms were found to better fit the Langmuir than the Freundlich model, and the adsorption kinetics fitted a pseudo-second-order model. The maximum adsorption at 303 K was 714-847 mg g À1. Thermodynamic studies revealed the adsorption of methylene blue to be spontaneous and exothermic. These results show that high-quality activated carbons can be produced from winemaking waste.

No abstract

No abstract

A concentrate obtained from mining tailings containing mainly cassiterite and columbotantalite was reduced for the production of tin metal. The compounds CaCO 3 , Na 2 CO 3 , K 2 CO 3 , and borax were used as fluxes in the pyrometallurgical reduction smelting process, and graphite was employed as the reducing agent. The greatest recovery of Sn (>95%) was obtained when using CaCO 3 as the flux; the purity of Sn was 96%. A slag equivalent to 25% of the mass of the initial concentrate was produced during the recovery of the Sn. This contained 45% Nb 2 O 5 and Ta 2 O 5 , adding extra value to the mine tailings. The tin metal ingot was purified by electrorefining involving a tin and H 2 SO 4 electrolyte solution and a 101.9 A/m 2 current applied for 148 h. Under these conditions, 90 wt % of the Sn in the ingot was recovered at a purity of 99.97%.

No abstract

This work describes the adsorption of Pb2+ in aqueous solution onto an activated carbon (AC) produced from winemaking waste (cluster stalks). After characterizing the AC using Fourier transform infrared spectroscopy (FTIR) and micro-Raman spectroscopy, the influence of different physico-chemical factors (stirring rate, temperature, pH, adsorbent concentration, etc.) on its capacity to adsorb Pb2+ was examined. Kinetic and thermodynamic studies showed that the adsorption of the Pb2+ follows a pseudo-second-order kinetic model and fits the Langmuir isotherm model, respectively. The maximum adsorption capacity of the AC was 58 mg/g at 288 K temperature and pH of 4. In conclusion, ACs made from waste cluster stalks could be successfully used to remove Pb2+ from polluted water.