Dynamic and equilibrium studies of the RDX removal from soil using CMC-coated zerovalent iron nanoparticles.

Rapid chemical degradation of toxic RDX explosive in soil can be accomplished using zerovalent nanoiron suspension stabilized in dilute carboxymethyl cellulose solution (CMC-ZVINs). The effect of operating conditions (redox-potential, Fe/RDX molar ratio) was studied on batchwise removal of RDX in contaminated soil. While anaerobic conditions resulted in 98% RDX removal in 3 h, only slightly over 60% RDX removal could be attained under aerobic conditions.

Optimization of a biosorption column performance.

The dynamics of copper and zinc biosorption by Sargassum fluitans was analyzed under variable column operating conditions including different column lengths (15 and 45 cm), metal-feed solution concentrations (1 and 6 meq L(-1)), metal-sorbent affinities (2.01 and 0.45), and interstitial velocities (12 and 4 cm min(-1)).

Column biosorption of lanthanum and europium by Sargassum.

Batch and column biosorption of La(3+) (lanthanum) and Eu(3+) (europium) was studied using protonated Sargassum polycystum biomass. The ion exchange sorption mechanism was confirmed by the proportional release of protons and by the total normality of the solution, which remained constant during the process. Equilibrium isotherms were determined for the binary systems, La/H and Eu/H for a total normality of 3 meq g(-1), which produced separation factors of 2.

Biosorption and me.

Biosorption has been defined as the property of certain biomolecules (or types of biomass) to bind and concentrate selected ions or other molecules from aqueous solutions. As opposed to a much more complex phenomenon of bioaccumulation based on active metabolic transport, biosorption by dead biomass (or by some molecules and/or their active groups) is passive and based mainly on the "affinity" between the (bio-)sorbent and sorbate. A personal overview of the field and its origins is given here, focusing on R&D reasoning and know-how that is not normally published in the scientific literature.

Biosorption of arsenic (V) with acid-washed crab shells.

Highly toxic arsenate occurs naturally in some well water as well as in industrial wastewaters. Removal of arsenate (As(V)) by biosorption with acid-washed crab shells (AWCS) is very sensitive to solution pH. It greatly increased when the solution pH was lowered from 3.

Comparative testing of tangential microfiltration for microbial cultures.

In an attempt to extend and intensify the productive periods of bioprocesses, a self-cleaning tangential filtration device was examined. Built into a special-design bioreactor, its cell retention was evaluated for continuous-flow operation with selected examples of bacteria (Escherichia coli), yeasts (Sacharomyces cerevisiae), and filamentous fungi (Aspergillus niger). Performance characteristics such as filtration rates and cell accumulation were assessed as a function of filter rotational speed, operating pressure, cultivation time, and microfilter type (i.

Behavior of the mass transfer zone in a biosorption column.

Modeling of the mass transfer zone behavior under variable conditions in a flow-through fixed-bed sorption column enabled the prediction of breakthrough curves for Cu2+ and Ca-preloaded Sargassum fluitans biomass. The mass transfer resistance, particle diffusion, and the axial dispersion were incorporated in the model. The dynamics of the mass transfer zone was described under variable sorption column operating conditions including different column lengths and fluid flow rates.

Stabilization of the initial electrochemical potential for a metal-based potentiometric titration study of a biosorption process.

An interactive metal-based potentiometric titration method has been developed using an ion selective electrode for studying the sorption of metal cations. The accuracy of this technique was verified by analyzing the metal sorption mechanism for the biomass of Rhizopus arrhizus fungus and diatomite, two dissimilar materials (organic and mineral, strong sorbent and weak sorbent) of a different order of cation exchange capacity. The problem of the initial electrochemical potential was addressed identifying the usefulness of a Na-sulfonic resin as a strong chelating agent applied before the beginning of sorption titration experiments so that the titration curves and the sorption uptake could be quantitatively compared.

Lead biosorption study with Rhizopus arrhizus using a metal-based titration technique.

Acid-base and metal-based potentiometric titration methods were used to analyze sorption mechanisms of lead by Rhizopus arrhizus fungal biomass. Biosorption was not considered globally but as the result of successive sorption reactions on various binding sites with different selectivities. Precipitation occurred rapidly when lead concentration increased.

Effect of counterions on lanthanum biosorption by Sargassum polycystum.

The effect of the presence of different anions on the biosorption of La(3+) (Lanthanum) using Sargassum polycystum Ca-loaded biomass was studied in this work. Different types of metal salts were used, such as nitrate, sulphate and chloride. The presence of the anion sulphate decreased the metal uptake for tested pH values of 3--5 when compared to the nitrate and chloride systems.

A high-resolution titrator: a new approach to studying binding sites of microbial biosorbents.

The high-resolution potentiometric titration was used as a physico-chemical method to study the acid properties of selected biosorbent materials in order to quantify the functional acidic groups for sorption and to determine their affinities by considering their partial or total ionization equilibrium reactions. The Gran's method and the Henderson-Hasselbach's equation were employed in establishing the partition of the total acidity as associated with strong, weak and very weak acidic chemical active groups. The differences in the total organic acidity (A(TO)) for the two selected types of bacteria and two mycelia revealed by this method were explained by the chemical composition of their cell walls.

Biosorption of La, Eu and Yb using Sargassum biomass.

Biosorption of the lanthanides: Lanthanum (La(3+)), Europium (Eu(3+)) and Ytterbium (Yb(3+)) from single-component and multi-component batch systems using Sargassum polycystum Ca-loaded biomass was studied. The ion exchange sorption mechanism was confirmed by the release of calcium ions from the biomass that matched the total number of metal and protons removed from the solution. The metal binding increased with pH due to the decrease of proton concentration in the system, as they also compete for the binding sites.

1H-NMR study of Na alginates extracted from Sargassum spp. in relation to metal biosorption.

The use of a number of species of marine brown algae in the implementation of bioremediation strategies for toxic heavy metals is being considered and evaluated. The biosorption capacity of these algae for heavy metals resides mainly in a group of linear polysaccharides known as alginates that occur as a gel in the algal thallus. The potential for selective metal binding by the biomass of two species of Sargassum was evaluated by 1H-NMR (nuclear magnetic resonance) following a high temperature, alkaline extraction and purification of their alginate polysaccharide.

A review of the biochemistry of heavy metal biosorption by brown algae.

The passive removal of toxic heavy metals such as Cd(2+), Cu(2+), Zn(2+), Pb(2+), Cr(3+), and Hg(2+) by inexpensive biomaterials, termed biosorption, requires that the substrate displays high metal uptake and selectivity, as well as suitable mechanical properties for applied remediation scenarios. In recent years, many low-cost sorbents have been investigated, but the brown algae have since proven to be the most effective and promising substrates. It is their basic biochemical constitution that is responsible for this enhanced performance among biomaterials.

Modeling of lithium interference in cadmium biosorption.

Biosorption of Cd by the brown seaweed Sargassum polycystum biomass was experimentally investigated and mathematically modeled at different pH and ionic strength levels. From the potentiometric titration of the biomass, three types of functional groups were identified, and the dissociation constant and the numbers of these groups were determined. The carboxyl group (pK(H) 3.

Metal selectivity of Sargassum spp. and their alginates in relation to their alpha-L-guluronic acid content and conformation.

The discovery of a consistent and unusual enrichment in homopolymeric alpha-L-guluronic acid G-blocks in alginates extracted from a suite of Sargassum brown algae is described in this study. 1H NMR spectroscopy was used to characterize these alginates which display homopolymeric guluronic acid block (G-block) frequency values (F(GG)) between 0.37 and 0.