lect 16 Flashcards
what is ion sorption?
-hydrated Mn oxides an bind cations or anions depending on the pH
-the pzc=2.8 to 4.5 and the SA 10^2m^2/g
-iron oxides and acid volatile sulfides can lead to sedimentation of heavy metals (depends on pE conditions)
-in the case of anion sorption on metal hydroxide surfaces, the binding is harder to explain than in the case of cations
what is the adsorption of cations?
what is the adsorption of anions?
what is the aggregation of colloidal particles?
-coagulation
-flocculation
what is coagulation?
involved the reduction of this electrostatic repulsion such that colloidal particles of identical materials may aggregate
what is flocculation?
uses bridging compounds, which form chemically bonded links between colloidal particles and enmesh the particles in relatively large masses called floc networks
what do hydrophobic colloids do (Aggregation of colloidal particles)?
-hydrophobic colloids that are stabilized by electrostatic repulsion may be coagulated by the addition of small quantities of salts that contribute ions to solution, which reduces the electrostatic repulsion between particles. because it acts upon the double layer of electrical charge surrounding a charged particle, this mechanism is called double-layer compression
what are polyelectrolytes?
polyelectrolytes of both natural and synthetic origin may cause colloids to flocculate
-polyelectrolytes are polymers with a high formula mass that normally contain ionizable functional groups
what is the graph of coagulation-flocculation?
what is adsorption? what is Freundlich isotherm?
recall: the surface energy level may be lowered by reduction in surface area. Normally, this reduction is accomplished by aggregation particles or by adsorption of solute species
-the degree of adsorption of organic compounds is often inversely proportional to their water solubility
-freudlich isotherm: X is the amount of adsorbed species per unit mass of adsorbent
what are adsorption isotherms?
what can pollutants compounds be bound as?
pollutant compounds, including pesticides and their metabolites, plasticizers, halogenated aromatic compounds, and nitro compounds become covalently attached as bound residues to humic substances in sediments and soil. This pathway can remove toxic components from water and result in a reduction in toxicity
what are organic compounds on sediments and suspended matter?
-colloids: play a role in the transport of contaminants (mobility.distribution)
-different chem/biochemical degradation pathways compared with bulk solution
-clays can adsorb humic materials which can further lead to addition adsorption of organics
what can we consider adsorption as?
consider adsorption as a reversible process and its role in the transfer (release) of contaminants to biological receptors (direct versus indirect transfer pathway)
-transfer of contaminants in sediment to organisms, where they may have an effect by acting on a biochemical receptor
what is the research objective of the colloid paper?
-the aim of the present work was to examine and compare the adsorption and desorption of HA and FA on SiO2 particles with different size.
Factors such as pH and ionic strength that were assumed to influence the adsorption were investigated in order to explore the relevant mechanisms
what are humic and fulvic acids?
-humic acid: a material that precipitates from the acidified extract (less soluble) and contain more aromatic groups vs. aliphatic groups
-fulvic acid: an organic material that remains in the acidified solution (more soluble), richer is carboxylic acids, phenolic, and ketonic groups. More aliphatic groups that humic acids
what are the generalized molecular structures of fulvic and humic acid?
what is hydrated alumina?
what are the ionic strength effects and pH of fulvic and humic acid?
what were the conclusions of the paper?
