Uptake of cobalt and cesium by microalgal- and cyanobacterial-clay mixtures

Abstract

Accumulation of cobalt and cesium by the microalga Scenedesmus obliquus and the cyanobacterium Synechocystis PCC 6803 has been characterized at metal concentrations ranging from 1-100 µM in the presence of three clay minerals, montmorillonite, illite, and kaolinite. The majority of metal uptake over a 4 h period consisted of rapid binding to the clay mineral-cell aggregates, and was unaffected by incubation in the dark or by the presence of the metabolic inhibitor carbonyl cyanide-3-chlorophenyl hydrazone (CCCP). This was followed by a slower, energy-dependent uptake of metal by the cell components of the mixtures, which was inhibited by incubation in the dark or in the presence of CCCP. The initial phase of uptake by the clay mineral-cell mixtures and mixture components alone conformed to a Freundlich adsorption isotherm, the order of uptake for both cobalt and cesium being montmorillonite-cells > illite-cells > kaolinite-cells. S. obliquus-clay mineral mixtures accumulated more cobalt and cesium than Synechocystis PCC 6803-clay mineral mixtures. On a dry weight basis, clay minerals alone accumulated greater amounts of metals than clay mineral-cell mixtures, which accumulated more than the cells alone. However, when the same data was expressed as amount of metal adsorbed per unit surface area, S. obliquus, in most cases, adsorbed greater amounts of cobalt and cesium than the clay minerals or Synechocystis PCC 6803. As the proportion of clay in a cell-clay mineral mixture was increased, the amount of metal accumulated also increased. Reduced accumulation of cobalt and cesium by cell-clay mineral mixtures, exhibited by equal amounts of the individual components added together, indicated that the formation of clay-cell aggregates had masked some of the binding sites normally available to metal ions. Accumulation of cobalt and cesium by all clay mineral-cell mixtures was dependent on the external pH and NaCl concentration, and decreased with decreasing pH and increasing external NaCl concentration.

Biosorption: critical review of scientific rationale, environmental importance and significance for pollution treatment

“…clay minerals which are one of the most important metal-sorbing components in soils. 54,166 It may be concluded that biosorption phenomena have a more significant role in metal/radionuclide speciation, bioavailability and mobility in aquatic and terrestrial environments than has previously been supposed. 85,167 -169 Further, it should be emphasized that accompanying nucleation and precipitation can lead to biomineral formation.…”

Metals, minerals and microbes: geomicrobiology and bioremediation

“…Microbes are major components of the soil while biogenic particles dominate oceanic detrital phases (Stumm & Morgan, 1996). Many studies have shown that microbial cells, on a specific unit area basis, can exhibit higher sorption values for metals than even clay minerals (Garnham et al, 1993;Morley & Gadd, 1995). It is possible that biosorption phenomena have a more significant role in metal/radionuclide speciation, bioavailability and mobility in the biosphere than has previously been supposed (Krantz-Rulcker et al, 1993Ledin et al, 1996;McLean et al, 2002); it should be emphasized that this may also accompany or precede nucleation, precipitation and biomineral formation (Burford et al, 2003a;Gadd, 2007Gadd, , 2009a.…”

Phytoremediation

“…These include archaea, bacteria (Pinaki et al 2004 ;Bueno et al 2008 ;Vijayaraghavan et al 2007 ;Tuzen et al 2008 ;Ngwenya 2007 ;Calfa and Torem 2008 ), cyanobacteria (Pradhan et al 2007 ;Kiran et al 2007 ;Anjana et al 2007 ;Avery et al 1993 ;Garnham et al 1993a ;Garnham et al 1993b ;Garnham et al 1993c ), algae (Garnham et al 1991 ;Garnham et al 1992a ;Garnham et al 1992b ;Garnham 1997 ;Mohan et al 2007 ;Aksu and Donmez 2006 ) (including macroalgae, i.e., seaweeds (Davis et al 2003 ;Yang and Chen 2008 ;Vilar et al 2008 ;Senthilkumar et al 2007 ;Romera et al 2007 ;Murphy et al 2007 ;Webster and Gadd 1996 ;Webster et al 1997 )), and fungi, the latter including fi lamentous forms (Tobin et al 1994 ;Gadd and White 1992 ;Kapoor and Viraraghavan 1995 ;Kiran et al 2006 ;Bayramoglu and Arica 2007 ;Zhou 1999 ), as well as unicellular yeasts (Wang and Chen 2006 ;de Rome and Gadd 1991 ;de Rome and Gadd 1987b ), fruiting bodies (mushrooms, brackets, etc. ), and lichens (Sari et al 2007 ;…”