Surface Behaviour of β-FeOOH: Point of Zero Change and Interactions with Anions and Cations

1986 ◽  
Vol 3 (2) ◽  
pp. 89-94 ◽  
Author(s):  
K. M. Parida
Keyword(s):  
Potentiometric Titration ◽  
Electrical Double Layer ◽  
Aqueous Suspension ◽  
Zero Point ◽  
Monovalent Cations ◽  
Addition Method ◽  
Acid Base ◽  
Solution Interface ◽  
Zero Point Of Charge ◽  
Anions And Cations

The acid-base dissociation behaviour of the surface of β-FeOOH in aqueous suspension has been investigated by potentiometric titration. The zero point of charge of the electrical double layer of the oxide/solution interface (pH = 7·6 ± 0·1 in KNO3, NaNO3 and LiNO3 electrolytes) coincides with the pH of the isoelectric point, determined by the solid addition method. Chloride and sulphate anions are strongly adsorbed on the β-FeOOH surface and thus modify the balance of positive and negative groups on the surface. The sequence of interaction of monovalent cations with the surface is K+ = ≤ Na+ ≤ Li+. β-FeOOH appears to behave essentially in the same manner as found previously for α-FeOOH.

THE ZERO POINT OF CHARGE OF OXIDES1

1962 ◽  
Vol 66 (6) ◽  
pp. 967-973 ◽  
Author(s):  
G. A. Parks ◽  
P. L. de Bruyn
Keyword(s):  
Zero Point ◽  
Zero Point Of Charge

Surface Chemistry of Mesoporous Materials: Effect of Nanopore Confinement

2002 ◽  
Vol 751 ◽  
Author(s):  
Yifeng Wang ◽  
Charles Bryan ◽  
Huifang Xu ◽  
Huizhen Gao
Keyword(s):  
Surface Chemistry ◽  
Surface Acidity ◽  
Scale Space ◽  
Acid Base ◽  
Acidity Constants ◽  
Solution Interface ◽  
Ion Sorption ◽  
Alumina Particles ◽  
The Difference ◽  
Nanopore Confinement

AbstractAcid-base titration and metal sorption experiments were performed on both mesoporous alumina and alumina particles under various ionic strengths. It has been demonstrated that surface chemistry and ion sorption within nanopores can be significantly modified by a nano-scale space confinement. As the pore size is reduced to a few nanometers, the difference between surface acidity constants (ΔpK = pK2 – pK1) decreases, giving rise to a higher surface charge density on a nanopore surface than that on an unconfined solid-solution interface. The change in surface acidity constants results in a shift of ion sorption edges and enhances ion sorption on that nanopore surfaces.

Lead(II) Adsorption by Raw and Acid-Activated Vermiculite

2012 ◽  
Vol 557-559 ◽  
pp. 1127-1130 ◽  
Author(s):  
Wen Jun Xiang
Keyword(s):  
Specific Surface ◽  
Surface Charge ◽  
Langmuir Isotherm ◽  
Cation Exchange Capacity ◽  
Zero Point ◽  
Exchange Capacity ◽  
Zero Point Of Charge ◽  
Adsorption Capacities ◽  
Adsorption Data ◽  
Hcl Solution

Acid-activated vermiculite (AAV) was prepared by treating raw vermiculite (RV) at 80°C with HCl solution. The surface properties and Pb(II) adsorption characteristics of RV and AAV were studied. The specific surface area (SSA), cation exchange capacity (CEC), pH at zero point of charge (pHZPC), and surface charge at pH 5.8 of AAV were 287.62 m2/g, 24.85 cmol/kg, pH 3.06, and -0.361 mmol/g, respectively. Compared to RV, the SSA, CEC and surface charge of AAV increased, but the value of pHZPC decreased. At pH 5.8, the maximum adsorption capacities (qmax) for Pb(II) of RV and AAV were 10.72 and 18.53 mg/g, respectively. The adsorption data for Pb(II) by RV and AAV could be well fitted using Langmuir isotherm (R2 =0.990 and 0.995, respectively)

scholarly journals K(+)- and HCO3(-)-dependent acid-base transport in squid giant axons II. Base influx.

1995 ◽  
Vol 106 (5) ◽  
pp. 845-862 ◽  
Author(s):  
E M Hogan ◽  
M A Cohen ◽  
W F Boron
Keyword(s):  
Monovalent Cations ◽  
Plateau Phase ◽  
Passive Transport ◽  
Simultaneous Presence ◽  
Dialysis Fluid ◽  
Acid Base ◽  
Giant Axons ◽  
Conductive Pathway ◽  
Stilbene Derivatives ◽  
Disulfonic Stilbene

We used microelectrodes to determine whether the K/HCO3 cotransporter tentatively identified in the accompanying paper (Hogan, E. M., M. A. Cohen, and W. F. Boron. 1995. Journal of General Physiology. 106:821-844) can mediate an increase in the intracellular pH (pHi) of squid giant axons. An 80-min period of internal dialysis increased pHi to 7.7, 8.0, or 8.3; the dialysis fluid was free of K+, Na+, and Cl-. Our standard artificial seawater (ASW), which also lacked Na+, K+, and Cl-, had a pH of 8.0. Halting dialysis unmasked a slow pHi decrease. Subsequently introducing an ASW containing 437 mM K+ and 0.5% CO2/12 mM HCO3- had two effects: (a) it caused membrane potential (Vm) to become very positive, and (b) it caused a rapid pHi decrease, because of CO2 influx, followed by a slower plateau-phase pHi increase, presumably because of inward cotransport of K+ and HCO3- ("base influx"). Only extracellular Rb+ substituted for K+ in producing the plateau-phase pHi increase in the presence of CO2/HCO3-. Mean fluxes with Na+, Li+, and Cs+ were not significantly different from zero, even though Vm shifts were comparable for all monovalent cations tested. Thus, unless K+ or Rb+ (but not Na+, Li+, or Cs+) somehow activates a conductive pathway for H+, HCO3-, or both, it is unlikely that passive transport of H+, HCO3-, or both makes the major contribution to the pHi increase in the presence of K+ (or Rb+) and CO2/HCO3-. Because exposing axons to an ASW containing 437 mM K+, but no CO2/HCO3-, produced at most a slow pHi increase, K-H exchange could not make a major contribution to base influx. Introducing an ASW containing CO2/HCO3-, but no K+ also failed to elicit base influx. Because we observed base influx when the ASW and DF were free of Na+ and Cl-, and because the disulfonic stilbene derivatives SITS and DIDS failed to block base influx, Na(+)-dependent Cl-HCO3 exchange also cannot account for the results. Rather, we suggest that the most straightforward explanation for the pHi increase we observed in the simultaneous presence of K+ and CO2/HCO3- is the coupled uptake of K+ and HCO3-.

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