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- Uptake and release of divalent zinc ions from aqueous solutions by aquatic moss Fontinalis antipyretica.Publication . Martins, Ramiro; Boaventura, RuiAquatic mosses are able to accumulate zinc and some other heavy metal ions from aqueous solutions and partially release them when exposed to metal-free water. They play an important role in the assessment of toxic elements in water. The advantage of mosses over direct water sampling is that the use of the former lessens spatial and temporal variations, enhances the level of contaminant identification by concentrating toxic elements, and provides information relative to the bioavailable species. However, to make the concentration of metals that can be measured in mosses a reliable indicator of the concentration of toxic elements in the water, we need to model the bioaccumulation phenomenon. Laboratory experiments were conducted to determine zinc uptake and release kinetics by the aquatic moss Fontinalis antipyretica, as this species is widely spread in Portuguese rivers and the majority of the European countries. Zinc was chosen for this study because (i) it acts as micro-nutrient for plant growth in low concentration values; (ii) it is toxic when in excess inhibiting the growth and (iii) it is present in many industrial wastewaters and mine drainage waters discharged into rivers and lakes.
- Application of aquatic mosses to decontaminate industrial effluentsPublication . Martins, Ramiro; Boaventura, RuiAs biosorption is a low cost and effective method for treating metal-bearing wastewaters, understanding the process kinetics is relevant for design purposes. In the present study, the performance of the aquatic moss Fontinalis antipyretica for removing cadmium and lead from simulated wastewaters has been evaluated. Five kinetic models (first-order, pseudo-first-order, Elovich, Ritchie second-order and pseudo- second-order) were fitted to the experimental data and compared. Previously, the effect of parameters such as the initial solution pH, contact time, and initial metal ion concentration on biosorption was investigated using a sorbent dose of 2 g l-1. The initial pH of the solution was found to have an optimum value in the range of 4.0-6.0. The equilibrium sorption capacity of cadmium and lead by Fontinalis antipyretica increased with the initial metal concentration. For an initial metal concentration of 10 mg l-1, the uptake capacity of the moss, at equilibrium, is the same for both metals (4.8 mg g-1). Nevertheless, when the initial concentration increases up to 100 mg l-1, the uptake of Pb(II) is higher than 78%. The pseudo-second order biosorption kinetics provided the better correlation with the experimental data .
- Kinetic modelling of cadmium and lead removal by aquatic mossesPublication . Martins, Ramiro; Vilar, Vítor J.P.; Boaventura, RuiBecause biosorption is a low cost and effective method for treating metal-bearing wastewaters, understanding the process kinetics is relevant for design purposes. In the present study, the performance of the aquatic moss Fontinalis antipyretica for removing cadmium and lead from simulated wastewaters has been evaluated. Five kinetic models (first-order, pseudo-first-order, Elovich, modified Ritchie second-order and pseudo-second-order) were fitted to the experimental data and compared. Previously, the effect of parameters such as the initial solution pH, contact time, and initial metal ion concentration on biosorption was investigated. The initial pH of the solution was found to have an optimum value in the range of 4.0-6.0. The equilibrium sorption capacity of cadmium and lead by Fontinalis antipyretica increased with the initial metal concentration. For an initial metal concentration of 10 mg L-1, the uptake capacity of the moss, at equilibrium, is the same for both metals (4.8 mg g-1). Nevertheless, when the initial concentration increases up to 100 mg L-1, the uptake of Pb(II) was higher than 78%. The pseudo-second order biosorption kinetics provided the better correlation with the experimental data (R2 ≥ 0.999).
- Removal of zinc by biomass of aquatic mossesPublication . Martins, Ramiro; Boaventura, RuiThe utilization of aquatic mosses for the treatment of wastewater containing heavy metals is gaining more attention as a simple, effective and economic means of pollution remediation. The effect of various parameters such as contact time, initial metal ion concentration and temperature on zinc biosorption onto the aquatic moss Fontinalis antipyretica was studied. The maximum zinc uptake by Fontinalis antipyretica in batch system at pH 5.0, adsorbent dose of 2 g l-1 and 20ºC was found to be 15.4 mg g-1. Langmuir and Freundlich isotherm models fit de experimental data. Results showed that nonliving biomass of Fontinalis antipyretica is a suitable biosorbent for zinc.
- Cadmium(II) and zinc(II) adsorption by the aquatic moss Fontinalis antipyretica: Effect of temperature, pH and water hardnessPublication . Martins, Ramiro; Pardo, Rosana; Boaventura, RuiThe biosorption of cadmium(II) and zinc(II) ions onto dried Fontinalis antipyretica, a widely spread aquatic moss, was studied under different values of temperature, initial pH and water hardness. The equilibrium was well described by Langmuir adsorption isotherms. Maximum biosorption capacity of cadmium was independent on temperature and averaged 28.0mg g 1 moss, whereas for zinc, capacity increased with temperature, from 11.5mg g 1 moss at 5 C to 14.7mg g 1 moss at 30 C. Optimum adsorption pH value was determined as 5.0 for both metal ions. Cadmium uptake was unaffected by the presence of calcium ions, but zinc sorption was improved when water hardness increased from 101.1 to 116.3mg CaCO3 l 1. Inversely, as hardness increases, the competition with calcium ions strongly reduces the affinity of the biosorbent for zinc.
- Removal of copper and nickel onto low cost adsorbent: aquatic mossesPublication . Martins, Ramiro; Boaventura, RuiA realistic scenario is that man’s use of metals seriously began to affect the environment during the Industrial Revolution. Today, two thousand years later, we can say to be in the Metal Removal Age and we are all too aware of the risks inherent to the uncontrolled dissemination of heavy metals into the environment. From the environmental point of view, the metals that are of greatest concern are those that, either by their presence or their accumulation, can have a toxic or an inhibitory effect on living beings. Metals can be dispersed, both naturally and by man’s activities, into any of the earth’s compartments: water, soil or air. However, the water and wastewater will be the main focus of this work.