Juscimar Silva | EMBRAPA - Empresa Brasileira de Pesquisa Agropecuária (original) (raw)
Papers by Juscimar Silva
The geochemical fates of Fe and As are so closely correlated that methods of As removal from cont... more The geochemical fates of Fe and As are so closely correlated that methods of As removal from contaminated water are in general based on the high affinity of this metalloid for Fe (hydr)oxides. Dissimilatory Fe reducing bacteria, however, play a fundamental role in catalysing the redox transformations that ultimately control the mobility of As in anoxic environments. The potential of Al-goethites in adsorbing As(V) compared with hematite, goethite, ferrihydrite, and gibbsite, and the stability of As-rich sludge under anoxic conditions were investigated in this study. Arsenate adsorption maxima and its isotherm adsorption at different pH were measured following Fe (hydr)oxides synthesis. Arsenic loaded samples were anaerobically incubated in the presence of Shewanella putrefaciens cells, and the solution was periodically sampled to evaluate the contents of soluble As and Fe. The As(V)
Water, Air, & Soil Pollution, 2012
Dissimilatory iron-reducing bacteria play a fundamental role in catalysing the redox transformati... more Dissimilatory iron-reducing bacteria play a fundamental role in catalysing the redox transformations that ultimately control the mobility of As in anoxic environments, a process also controlled by the presence of competing anions. In this study, we investigated the decoupling of As from loaded Al and Fe (hydr)oxides by competing anions in the presence of iron-reducing bacteria. Hematite, goethite, ferrihydrite, gibbsite and three aluminium-substituted goethites (AlGts) were synthesised and loaded with arsenate, followed by anaerobic incubation with different phosphate or carbonate-containing media in the presence of catalytic iron-reducing bacteria. Soluble Al, As, Fe and P contents were measured in aliquots by inductively coupled plasma optical emission spectrometry following periodical sampling. Shewanella putrefaciens cells were able to utilise both noncrystalline and crystalline Fe (hydr)oxides as electron acceptors, releasing Fe and As into solution. Phosphate and carbonate affected the Fe bioreduction, probably due to the precipitation of metastable mineral phases and also to phosphate-induced stabilisation on the hydroxide surfaces. Phosphate precipitation acted as a sink for As, thus limiting its mobilisation. The highest fraction of desorbed As by phosphate was observed for gibbsite, followed by AlGts. Similarly, gibbsite showed significant amounts of arsenate displaced by carbonate. In spite of its low crystallinity, ferrihydrite was the most efficient compound in retaining arsenate, possibly due to As co-precipitation. This study provides new insight into the management of As-contaminated soils and sediments containing Algoethites and gibbsite, where the Fe activity may be too low to co-precipitate As-bearing vivianite. Thus, the dynamics of As(V) in flooded soils are significant in agriculture and environmental management.
The geochemical fates of iron and arsenic are so closely correlated that methods of arsenic remov... more The geochemical fates of iron and arsenic are so closely correlated that methods of arsenic removal from water are in general based on the high adsorptive affinity of this metalloid with iron (hydr)oxides. Under anoxic conditions, however, reductive dissolution of iron (hydr)oxides can take place, and arsenic may be released into the surrounding environment. The purpose of this study was to investigate the potential of Al-substituted goethites in adsorbing arsenic compared with other Fe and Al (hydr)oxides. Hematite (Hm), goethite (Gt), 2-line ferrihydrite (Fh), gibbsite (Gb), aluminium hydroxide, and three Al-substituted goethites (AlGt) were synthesized and characterized by X-ray powder diffraction (XRD), particle size analysis, and diffuse reflectance (DR) spectroscopy. Adsorption isotherms were obtained after shaking the samples with increasing concentrations of arsenate (40 -1600 mg L -1 ) in a 10 mmol L -1 CaCl 2 solution for 24 hours. The adsorption envelope was measured at pH ranging from 3 to 9. The As(V) adsorption maxima decreased in the following order: Al(OH) 3 > Fh > AlGt-15 > AlGt-25 > AlGt-35 > Hm > Gb > Gt. No relationship was observed between particle diameter and maximum adsorption, suggesting that re-aggregation could have taken place, or possibly that imperfections on the surface of the particles increased their surface net charge, resulting in high adsorption density. The behaviour of all samples was strongly dependent on pH, and the maximum adsorption was achieved in slightly acidic conditions. In general, Al-substituted goethites showed promising results for their potential use as an adsorbent to remove arsenic from water.
Water Research, 2010
The geochemical fates of Fe and As are so closely correlated that methods of As removal from cont... more The geochemical fates of Fe and As are so closely correlated that methods of As removal from contaminated water are in general based on the high affinity of this metalloid for Fe (hydr)oxides. Dissimilatory Fe reducing bacteria, however, play a fundamental role in catalysing the redox transformations that ultimately control the mobility of As in anoxic environments. The potential of Al-goethites in adsorbing As(V) compared with hematite, goethite, ferrihydrite, and gibbsite, and the stability of As retained by the Fe compounds under anoxic conditions were investigated in this study. The (hydr)oxides were synthesised, and adsorption isotherms and As(V) adsorption maxima at different pH were measured. Arsenic loaded samples were anaerobically incubated in the presence of Shewanella putrefaciens, and periodically sampled to evaluate the contents of soluble As and Fe. The As(V) adsorption maxima decreased in the following order: Fh > AlGt13 > AlGt20 > AlGt23 > Gb > Hm > Gt. In terms of surface area, Gb, Gt, and Hm showed higher As(V) loading capacity than Fh, suggesting available reactive sites not fully occupied by arsenate on Fh. The same hypothesis can be considered for Al-goethites, as they showed even lower arsenate loading capacity per surface area. The presence of structural Al in the goethites enhanced considerably the As uptake capacity and stability under reducing conditions. Therefore, the Al-goethites showed good potential as adsorbents to remove As from water. S. putrefaciens cells were able to utilise both noncrystalline and crystalline Fe (hydr)oxides as electron acceptors, releasing As into solution. Al-goethites showed a decrease in Fe and As mobilisation as structural Al increased.
The geochemical fates of Fe and As are so closely correlated that methods of As removal from cont... more The geochemical fates of Fe and As are so closely correlated that methods of As removal from contaminated water are in general based on the high affinity of this metalloid for Fe (hydr)oxides. Dissimilatory Fe reducing bacteria, however, play a fundamental role in catalysing the redox transformations that ultimately control the mobility of As in anoxic environments. The potential of Al-goethites in adsorbing As(V) compared with hematite, goethite, ferrihydrite, and gibbsite, and the stability of As-rich sludge under anoxic conditions were investigated in this study. Arsenate adsorption maxima and its isotherm adsorption at different pH were measured following Fe (hydr)oxides synthesis. Arsenic loaded samples were anaerobically incubated in the presence of Shewanella putrefaciens cells, and the solution was periodically sampled to evaluate the contents of soluble As and Fe. The As(V)
Water, Air, & Soil Pollution, 2012
Dissimilatory iron-reducing bacteria play a fundamental role in catalysing the redox transformati... more Dissimilatory iron-reducing bacteria play a fundamental role in catalysing the redox transformations that ultimately control the mobility of As in anoxic environments, a process also controlled by the presence of competing anions. In this study, we investigated the decoupling of As from loaded Al and Fe (hydr)oxides by competing anions in the presence of iron-reducing bacteria. Hematite, goethite, ferrihydrite, gibbsite and three aluminium-substituted goethites (AlGts) were synthesised and loaded with arsenate, followed by anaerobic incubation with different phosphate or carbonate-containing media in the presence of catalytic iron-reducing bacteria. Soluble Al, As, Fe and P contents were measured in aliquots by inductively coupled plasma optical emission spectrometry following periodical sampling. Shewanella putrefaciens cells were able to utilise both noncrystalline and crystalline Fe (hydr)oxides as electron acceptors, releasing Fe and As into solution. Phosphate and carbonate affected the Fe bioreduction, probably due to the precipitation of metastable mineral phases and also to phosphate-induced stabilisation on the hydroxide surfaces. Phosphate precipitation acted as a sink for As, thus limiting its mobilisation. The highest fraction of desorbed As by phosphate was observed for gibbsite, followed by AlGts. Similarly, gibbsite showed significant amounts of arsenate displaced by carbonate. In spite of its low crystallinity, ferrihydrite was the most efficient compound in retaining arsenate, possibly due to As co-precipitation. This study provides new insight into the management of As-contaminated soils and sediments containing Algoethites and gibbsite, where the Fe activity may be too low to co-precipitate As-bearing vivianite. Thus, the dynamics of As(V) in flooded soils are significant in agriculture and environmental management.
The geochemical fates of iron and arsenic are so closely correlated that methods of arsenic remov... more The geochemical fates of iron and arsenic are so closely correlated that methods of arsenic removal from water are in general based on the high adsorptive affinity of this metalloid with iron (hydr)oxides. Under anoxic conditions, however, reductive dissolution of iron (hydr)oxides can take place, and arsenic may be released into the surrounding environment. The purpose of this study was to investigate the potential of Al-substituted goethites in adsorbing arsenic compared with other Fe and Al (hydr)oxides. Hematite (Hm), goethite (Gt), 2-line ferrihydrite (Fh), gibbsite (Gb), aluminium hydroxide, and three Al-substituted goethites (AlGt) were synthesized and characterized by X-ray powder diffraction (XRD), particle size analysis, and diffuse reflectance (DR) spectroscopy. Adsorption isotherms were obtained after shaking the samples with increasing concentrations of arsenate (40 -1600 mg L -1 ) in a 10 mmol L -1 CaCl 2 solution for 24 hours. The adsorption envelope was measured at pH ranging from 3 to 9. The As(V) adsorption maxima decreased in the following order: Al(OH) 3 > Fh > AlGt-15 > AlGt-25 > AlGt-35 > Hm > Gb > Gt. No relationship was observed between particle diameter and maximum adsorption, suggesting that re-aggregation could have taken place, or possibly that imperfections on the surface of the particles increased their surface net charge, resulting in high adsorption density. The behaviour of all samples was strongly dependent on pH, and the maximum adsorption was achieved in slightly acidic conditions. In general, Al-substituted goethites showed promising results for their potential use as an adsorbent to remove arsenic from water.
Water Research, 2010
The geochemical fates of Fe and As are so closely correlated that methods of As removal from cont... more The geochemical fates of Fe and As are so closely correlated that methods of As removal from contaminated water are in general based on the high affinity of this metalloid for Fe (hydr)oxides. Dissimilatory Fe reducing bacteria, however, play a fundamental role in catalysing the redox transformations that ultimately control the mobility of As in anoxic environments. The potential of Al-goethites in adsorbing As(V) compared with hematite, goethite, ferrihydrite, and gibbsite, and the stability of As retained by the Fe compounds under anoxic conditions were investigated in this study. The (hydr)oxides were synthesised, and adsorption isotherms and As(V) adsorption maxima at different pH were measured. Arsenic loaded samples were anaerobically incubated in the presence of Shewanella putrefaciens, and periodically sampled to evaluate the contents of soluble As and Fe. The As(V) adsorption maxima decreased in the following order: Fh > AlGt13 > AlGt20 > AlGt23 > Gb > Hm > Gt. In terms of surface area, Gb, Gt, and Hm showed higher As(V) loading capacity than Fh, suggesting available reactive sites not fully occupied by arsenate on Fh. The same hypothesis can be considered for Al-goethites, as they showed even lower arsenate loading capacity per surface area. The presence of structural Al in the goethites enhanced considerably the As uptake capacity and stability under reducing conditions. Therefore, the Al-goethites showed good potential as adsorbents to remove As from water. S. putrefaciens cells were able to utilise both noncrystalline and crystalline Fe (hydr)oxides as electron acceptors, releasing As into solution. Al-goethites showed a decrease in Fe and As mobilisation as structural Al increased.