Nickel removal from exhausted electroplatting baths by using vegetable wastes

During the last years our research group has been studying the use of industrial vegetable wastes as grape stalks and exhausted coffee to remove metals ions such as Ni(II), Cu(II), Pb(II), Zn(II), Cd(II) or Cr(VI) and Cr(III) in aqueous solution from the point of view to use these wastes as biosorbents in a low cost alternative to activated carbon for wastewater treatment. The optimal experimental conditions for the removal of each of these metal ions in synthetic solutions by using both biosorbents were determined in previous studies . In this work, the performance of grape stalks and exhausted coffee for the removal of nickel ions from an exhausted electroplating bath of a metal finishing industry from Barcelona (Spain) has been investigated. Batch and column experiments were carried out at room temperature by using grape stalk wastes (particle size 0.8-1.0 mm), meanwhile in the case of exhausted coffee, two different particle size ranges were used, 0.25-0.50 mm and 0.50-1.00 mm for batch and column experiments, respectively. Kinetics and equilibrium studies were carried out in batch mode to determine the equilibrium contact time and to obtain the sorption capacity of sorbents. The data in both studies have been treated by using different models. Column experiments were designed to establish the optimal condition for the treatment of the industrial wastewater. The experiments were performed in packed bed up flow columns of different internal diameter and bed depth in order to predict the transport and sorption parameters. In all column experiments the flow rate was around 11 mL h-1. From perspective of process modelling, the dynamic behavior was described in terms of breakthrough curves. The bed depth service time (BDST), Thomas and Yoon Nelson models were used to analyze the experimental data and to determine model parameters. Batch results show that about 1hour was the time needed to reach equilibrium when using grape stalks and around 15 h when using exhausted coffee. In the case of exhausted coffee, the pH solution decreased during the sorption process from initial pH 5,5 to lower pH than the corresponding pHpzc (point zero charge). To avoid this, pH solution was controlled to a constant pH 5,5 and the equilibrium were achieved in 1h. Kinetic data of both sorption processes fit pseudo-second order model, indicating that chemisorption could be rate limiting in the sorption step. Equilibrium data of nickel sorption onto grape stalks and exhausted coffee fit adequately Langmuir model, indicating monolayer coverage. Results showed that maximum sorption capacity of grape stalks (4,8 10-2 mmol/g; 2,84 mg/g) is slightly higher than exhausted coffee (2,9 10-2 mmol/g; 1,70 mg/g). The maximum nickel sorption capacity of both sorbents was reduced to 50% compared to maximum sorption capacity determined using synthetic Ni(II) solutions. Thus, grape stalks and exhausted coffee performance for the removal of Ni(II) from the studied industrial wastewater are negatively affected by the presence of other compounds in the industrial wastewater. In column experiments, the best results were obtained by using 2.8 cm internal diameter columns and bed depth 6 cm and 8 cm for grape stalks and exhausted coffee, respectively. Breakthrough curves were successfully modelled by the proposed columns models. The results obtained demonstrated that grape stalks sorption capacity was higher than exhausted coffee but this one presented a higher sorption rate.Postprint (published version

Degradation of azo dyes by rapidly solidified metallic particles

Azo compounds are one of the most common families of dyes used in textile and leather treatments. An important step during the treatment of water polluted by these compounds, is the degradation of the compounds by decomposition of the -N=N- bonds, producing the de-colorization of the water. This de-colorization reaction can be activated by the presence of zero valent metallic particles. The metastable structures generated during rapid solidification tend to increase the chemical activity of the alloys. Recently, it has been discovered that the use of metallic particles in a metastable phase (amorphous or nanocrystalline) multiplies significantly the efficiency of the decolorization water-treatment step. Here we present the results obtained in the decolorization of water using alloys based on different metals (Fe, Mn, Ni and Al) produced by rapid solidification and posterior ball milling. For some Al-containing alloys the results show a fast reaction, even in neutral pH conditions. In this work, the efficiency of the different metastable alloys in the de-colorization process, the effects of the metastable structure and the processing conditions are presented and assessed.Peer ReviewedPostprint (published version

Dynamic light scattering plus scanning electron microscopy: usefulness and limitations of a simplified estimation of nanocellulose dimensions

Measurements of nanocellulose size usually demand very high-resolution techniques and tedious image processing, mainly in what pertains to the length of nanofibers. Aiming to ease the process, this work assesses a relatively simple method to estimate the dimensions of nanocellulose particles with an aspect ratio greater than 1. Nanocellulose suspensions, both as nanofibers and as nanocrystals, are subjected to dynamic light scattering (DLS) and to field-emission scanning electron microscopy (FE-SEM). The former provides the hydrodynamic diameter, as long as the scatter angle and the consistency are adequate. Assays with different angles and concentrations compel us to recommend forward scattering (12.8°) and concentrations around 0.05–0.10 wt %. Then, FE-SEM with magnifications of ×5000–×20,000 generally suffices to obtain an acceptable approximation for the actual diameter, at least for bundles. Finally, length can be estimated by a simple geometric relationship. Regardless of whether they are collected from FE-SEM or DLS, size distributions are generally skewed to lower diameters. Width distributions from FE-SEM, in particular, are well fitted to log-normal functions. Overall, while this method is not valid for the thinnest fibrils or for single, small nanocrystals, it can be useful in lieu of very high-resolution techniques.Peer ReviewedPostprint (published version

Nickel removal from exhausted electroplatting baths by using vegetable wastes

During the last years our research group has been studying the use of industrial vegetable wastes as grape stalks and exhausted coffee to remove metals ions such as Ni(II), Cu(II), Pb(II), Zn(II), Cd(II) or Cr(VI) and Cr(III) in aqueous solution from the point of view to use these wastes as biosorbents in a low cost alternative to activated carbon for wastewater treatment. The optimal experimental conditions for the removal of each of these metal ions in synthetic solutions by using both biosorbents were determined in previous studies . In this work, the performance of grape stalks and exhausted coffee for the removal of nickel ions from an exhausted electroplating bath of a metal finishing industry from Barcelona (Spain) has been investigated. Batch and column experiments were carried out at room temperature by using grape stalk wastes (particle size 0.8-1.0 mm), meanwhile in the case of exhausted coffee, two different particle size ranges were used, 0.25-0.50 mm and 0.50-1.00 mm for batch and column experiments, respectively. Kinetics and equilibrium studies were carried out in batch mode to determine the equilibrium contact time and to obtain the sorption capacity of sorbents. The data in both studies have been treated by using different models. Column experiments were designed to establish the optimal condition for the treatment of the industrial wastewater. The experiments were performed in packed bed up flow columns of different internal diameter and bed depth in order to predict the transport and sorption parameters. In all column experiments the flow rate was around 11 mL h-1. From perspective of process modelling, the dynamic behavior was described in terms of breakthrough curves. The bed depth service time (BDST), Thomas and Yoon Nelson models were used to analyze the experimental data and to determine model parameters. Batch results show that about 1hour was the time needed to reach equilibrium when using grape stalks and around 15 h when using exhausted coffee. In the case of exhausted coffee, the pH solution decreased during the sorption process from initial pH 5,5 to lower pH than the corresponding pHpzc (point zero charge). To avoid this, pH solution was controlled to a constant pH 5,5 and the equilibrium were achieved in 1h. Kinetic data of both sorption processes fit pseudo-second order model, indicating that chemisorption could be rate limiting in the sorption step. Equilibrium data of nickel sorption onto grape stalks and exhausted coffee fit adequately Langmuir model, indicating monolayer coverage. Results showed that maximum sorption capacity of grape stalks (4,8 10-2 mmol/g; 2,84 mg/g) is slightly higher than exhausted coffee (2,9 10-2 mmol/g; 1,70 mg/g). The maximum nickel sorption capacity of both sorbents was reduced to 50% compared to maximum sorption capacity determined using synthetic Ni(II) solutions. Thus, grape stalks and exhausted coffee performance for the removal of Ni(II) from the studied industrial wastewater are negatively affected by the presence of other compounds in the industrial wastewater. In column experiments, the best results were obtained by using 2.8 cm internal diameter columns and bed depth 6 cm and 8 cm for grape stalks and exhausted coffee, respectively. Breakthrough curves were successfully modelled by the proposed columns models. The results obtained demonstrated that grape stalks sorption capacity was higher than exhausted coffee but this one presented a higher sorption rate

Nickel removal from exhausted electroplatting baths by using vegetable wastes

During the last years our research group has been studying the use of industrial vegetable wastes as grape stalks and exhausted coffee to remove metals ions such as Ni(II), Cu(II), Pb(II), Zn(II), Cd(II) or Cr(VI) and Cr(III) in aqueous solution from the point of view to use these wastes as biosorbents in a low cost alternative to activated carbon for wastewater treatment. The optimal experimental conditions for the removal of each of these metal ions in synthetic solutions by using both biosorbents were determined in previous studies . In this work, the performance of grape stalks and exhausted coffee for the removal of nickel ions from an exhausted electroplating bath of a metal finishing industry from Barcelona (Spain) has been investigated. Batch and column experiments were carried out at room temperature by using grape stalk wastes (particle size 0.8-1.0 mm), meanwhile in the case of exhausted coffee, two different particle size ranges were used, 0.25-0.50 mm and 0.50-1.00 mm for batch and column experiments, respectively. Kinetics and equilibrium studies were carried out in batch mode to determine the equilibrium contact time and to obtain the sorption capacity of sorbents. The data in both studies have been treated by using different models. Column experiments were designed to establish the optimal condition for the treatment of the industrial wastewater. The experiments were performed in packed bed up flow columns of different internal diameter and bed depth in order to predict the transport and sorption parameters. In all column experiments the flow rate was around 11 mL h-1. From perspective of process modelling, the dynamic behavior was described in terms of breakthrough curves. The bed depth service time (BDST), Thomas and Yoon Nelson models were used to analyze the experimental data and to determine model parameters. Batch results show that about 1hour was the time needed to reach equilibrium when using grape stalks and around 15 h when using exhausted coffee. In the case of exhausted coffee, the pH solution decreased during the sorption process from initial pH 5,5 to lower pH than the corresponding pHpzc (point zero charge). To avoid this, pH solution was controlled to a constant pH 5,5 and the equilibrium were achieved in 1h. Kinetic data of both sorption processes fit pseudo-second order model, indicating that chemisorption could be rate limiting in the sorption step. Equilibrium data of nickel sorption onto grape stalks and exhausted coffee fit adequately Langmuir model, indicating monolayer coverage. Results showed that maximum sorption capacity of grape stalks (4,8 10-2 mmol/g; 2,84 mg/g) is slightly higher than exhausted coffee (2,9 10-2 mmol/g; 1,70 mg/g). The maximum nickel sorption capacity of both sorbents was reduced to 50% compared to maximum sorption capacity determined using synthetic Ni(II) solutions. Thus, grape stalks and exhausted coffee performance for the removal of Ni(II) from the studied industrial wastewater are negatively affected by the presence of other compounds in the industrial wastewater. In column experiments, the best results were obtained by using 2.8 cm internal diameter columns and bed depth 6 cm and 8 cm for grape stalks and exhausted coffee, respectively. Breakthrough curves were successfully modelled by the proposed columns models. The results obtained demonstrated that grape stalks sorption capacity was higher than exhausted coffee but this one presented a higher sorption rate

Use of vegetables wastes to remove nickel ions from exhausted electroplating baths

The ability of vegetable wastes such as grape stalks and exhausted coffee to remove metals ions from synthetic aqueous solutions has been demonstrated in various studies performed by our research group [Villaescusa et al. 2004; Valderrama et al. 2010]. In this work, the performance of these wastes to remove nickel ions from an exhausted electroplating bath of a metal finishing industry from Barcelona (Spain) has been investigated. The experiments were carried out at room temperature in packed bed flow-up columns of 250 mm of length and 25 mm internal diameter using grape stalk (GS) and exhausted coffee wastes (EC) particle size 0.5-1.0 mm and 0.8-1.0 mm, respectively. In all experiments nickel concentration was kept constant about 5500 mg dm-3 and pH, flow rate, and bed height were varied in order to predict nickel ions transport in the column. Breakthrough curves were successfully described by Bed depth service time (BDST), Thomas and Yoon Nelson models [Zhe et al. 2013]. Desorption studies were performed by using 0.1 mol dm-3 HCl as elution solution at the same flow-rate used for sorption experiments. The results obtained demonstrated that, in the studied experimental conditions, variation of initial pH, flow rate and bed height did not lead to significant differences on sorption capacity. The sorbent sorption capacity was higher for GS (20 mg•g-1) than for EC (12 mg•g-1) and metal recovery from the column was close to 50% and 10% for GS and EC, respectively

Use of vegetables wastes to remove nickel ions from exhausted electroplating baths

The ability of vegetable wastes such as grape stalks and exhausted coffee to remove metals ions from synthetic aqueous solutions has been demonstrated in various studies performed by our research group [Villaescusa et al. 2004; Valderrama et al. 2010]. In this work, the performance of these wastes to remove nickel ions from an exhausted electroplating bath of a metal finishing industry from Barcelona (Spain) has been investigated. The experiments were carried out at room temperature in packed bed flow-up columns of 250 mm of length and 25 mm internal diameter using grape stalk (GS) and exhausted coffee wastes (EC) particle size 0.5-1.0 mm and 0.8-1.0 mm, respectively. In all experiments nickel concentration was kept constant about 5500 mg dm-3 and pH, flow rate, and bed height were varied in order to predict nickel ions transport in the column. Breakthrough curves were successfully described by Bed depth service time (BDST), Thomas and Yoon Nelson models [Zhe et al. 2013]. Desorption studies were performed by using 0.1 mol dm-3 HCl as elution solution at the same flow-rate used for sorption experiments. The results obtained demonstrated that, in the studied experimental conditions, variation of initial pH, flow rate and bed height did not lead to significant differences on sorption capacity. The sorbent sorption capacity was higher for GS (20 mg•g-1) than for EC (12 mg•g-1) and metal recovery from the column was close to 50% and 10% for GS and EC, respectively.Postprint (published version

Use of vegetables wastes to remove nickel ions from exhausted electroplating baths

The ability of vegetable wastes such as grape stalks and exhausted coffee to remove metals ions from synthetic aqueous solutions has been demonstrated in various studies performed by our research group [Villaescusa et al. 2004; Valderrama et al. 2010]. In this work, the performance of these wastes to remove nickel ions from an exhausted electroplating bath of a metal finishing industry from Barcelona (Spain) has been investigated. The experiments were carried out at room temperature in packed bed flow-up columns of 250 mm of length and 25 mm internal diameter using grape stalk (GS) and exhausted coffee wastes (EC) particle size 0.5-1.0 mm and 0.8-1.0 mm, respectively. In all experiments nickel concentration was kept constant about 5500 mg dm-3 and pH, flow rate, and bed height were varied in order to predict nickel ions transport in the column. Breakthrough curves were successfully described by Bed depth service time (BDST), Thomas and Yoon Nelson models [Zhe et al. 2013]. Desorption studies were performed by using 0.1 mol dm-3 HCl as elution solution at the same flow-rate used for sorption experiments. The results obtained demonstrated that, in the studied experimental conditions, variation of initial pH, flow rate and bed height did not lead to significant differences on sorption capacity. The sorbent sorption capacity was higher for GS (20 mg•g-1) than for EC (12 mg•g-1) and metal recovery from the column was close to 50% and 10% for GS and EC, respectively

Degradation of azo dyes by rapidly solidified metallic particles

Azo compounds are one of the most common families of dyes used in textile and leather treatments. An important step during the treatment of water polluted by these compounds, is the degradation of the compounds by decomposition of the -N=N- bonds, producing the de-colorization of the water. This de-colorization reaction can be activated by the presence of zero valent metallic particles. The metastable structures generated during rapid solidification tend to increase the chemical activity of the alloys. Recently, it has been discovered that the use of metallic particles in a metastable phase (amorphous or nanocrystalline) multiplies significantly the efficiency of the decolorization water-treatment step. Here we present the results obtained in the decolorization of water using alloys based on different metals (Fe, Mn, Ni and Al) produced by rapid solidification and posterior ball milling. For some Al-containing alloys the results show a fast reaction, even in neutral pH conditions. In this work, the efficiency of the different metastable alloys in the de-colorization process, the effects of the metastable structure and the processing conditions are presented and assessed.Peer Reviewe

Degradation of azo dyes by rapidly solidified metallic particles

Azo compounds are one of the most common families of dyes used in textile and leather treatments. An important step during the treatment of water polluted by these compounds, is the degradation of the compounds by decomposition of the -N=N- bonds, producing the de-colorization of the water. This de-colorization reaction can be activated by the presence of zero valent metallic particles. The metastable structures generated during rapid solidification tend to increase the chemical activity of the alloys. Recently, it has been discovered that the use of metallic particles in a metastable phase (amorphous or nanocrystalline) multiplies significantly the efficiency of the decolorization water-treatment step. Here we present the results obtained in the decolorization of water using alloys based on different metals (Fe, Mn, Ni and Al) produced by rapid solidification and posterior ball milling. For some Al-containing alloys the results show a fast reaction, even in neutral pH conditions. In this work, the efficiency of the different metastable alloys in the de-colorization process, the effects of the metastable structure and the processing conditions are presented and assessed.Peer Reviewe