RESUMEN
The adsorption of malachite green (MG) from aqueous solution by waste green tea (WGT) biomass was investigated. A series of experiments in batch conditions were conducted in order to assess the MG removal on WGT, following adsorbent quantity and temperature influences. Maximum removal efficiency for untreated WGT was 89% (4 g biomass, 100 mL solution of 94 mg/L, 316 K). It was found that the adsorption of MG increased by increasing temperature from 296 to 316 K. Thermodynamic parameters (ΔH°, ΔS°, ΔG°) were calculated, and indicated that dye adsorption onto the studied biomass was endothermic and non-spontaneous. Six chemical treatments were tested (four acidic - H3PO4, H2SO4, HCl, and tartaric acid, one oxidant - H2O2, and one basic - NaOH) in order to study the chemical groups responsible for MG adsorption onto WGT biomass. The alkali and acidic treatments led to an increase of adsorption efficiency up to 92% and 95% (H2SO4) respectively. The FTIR spectroscopy results emphasized the modifications of the biomass surface and how these are influencing the adsorption process.
Asunto(s)
Colorantes de Rosanilina/química , Té , Contaminantes Químicos del Agua , Purificación del Agua , Adsorción , Biomasa , Peróxido de Hidrógeno , Concentración de Iones de Hidrógeno , Cinética , Soluciones , Temperatura , TermodinámicaRESUMEN
Acid Mine Drainages (AMDs) from Hanes and Valea Vinului (Romania) closed mines were considered for characterization and treatment using a local zeolitic volcanic tuff, ZVT, (Macicas, Cluj County, Romania). Water samples were collected from two locations, before and after discharging point in case of Hanes mine, and on three horizons in case of Valea Vinului mine. Physico-chemical (pH, total solid, heavy metal ions concentration) analyses showed that the environment is strongly affected by these AMD discharges even if the mines were closed years ago. Iron, manganese and zinc were the main pollutants identified in Hanes mine AMD, while zinc is the one mainly present in case of Valea Vinului AMD. A batch technique (no stirring) in which the ZVT was put in contact with the AMD sample was proposed as a passive remediation technique. ZVT successfully remove heavy metal ion from AMD. According to heavy metal ion concentrations, removal efficiencies are reaching 100%, varying as follows, Fe(2+)>Zn(2+)>Mn(2+). When the ZVT was compared with two cationic resins (strong, SAR and weak acid, WAR) the following series was depicted, SAR>ZVT>WAR.
Asunto(s)
Restauración y Remediación Ambiental/métodos , Metales Pesados/análisis , Minería , Contaminantes Químicos del Agua/análisis , RumaníaRESUMEN
Biosorption of cadmium ions from synthetic aqueous solution using popular Romanian fir tree sawdust (Abies Alba) as biosorbent, was investigated in this work. Prior to its utilization the considered biomass was washed, dried and sieved without further chemical treatments. The biosorbent was characterized using humidity, density and elemental analysis determinations and FTIR. FTIR analysis indicated that, on the biomass surface hydroxyl and carboxyl groups are presented. The effect of different biosorption parameters was studied. Higher biomass quantity, neutral pH, slightly elevated temperature and high cadmium ions concentration are all favouring the biosorption process. Equilibrium (Langmuir and Freundlich isotherm), kinetics and thermodynamics of the considered biosorption process were discussed in details. Equilibrium was best described by the Langmuir isotherm, while the kinetic of the process was best described by the pseudo-second-order model, suggesting monolayer coverage and a chemisorption process. Thermodynamic parameters showed that cadmium biosorption process on fir tree sawdust is an endothermic process.