Abstract:The
charging and aggregation properties of boron nitride nanospheres
(BNNSs) were investigated in the presence of electrolytes of different
compositions and valences in aqueous suspensions. The influence of
mono- and multivalent cations (counterions) and anions (coions) on
the colloidal stability of the negatively charged particles was studied
over a wide range of salt concentrations. For monovalent ions, similar
trends were determined in the stability and charging of the particles
irrespective of the salt com… Show more
“…Compared with monovalent cations, a much lower concentration of divalent cations induced a drastic BSC aggregation, which may be because high-valent cations can make the surface charge of BSCs less negative through the increased charge screening effect, which benefits aggregation 43 . Previous studies have found that the stronger the surface charge, the more significant the shielding effect of high-valent cations 18 . Figure 2 The average effective hydrodynamic diameters of the BSC particle aggregates changing with the experimental time.…”
Section: Resultsmentioning
confidence: 99%
“…Some scholars define this threshold value at 25 mV and called it 25 mV rule 52 . Later, researchers estimat the CCCs using 25 mV as a threshold of stability, and they found that 25 mV rule is clearly unreliable for low CCCs (< 100 mV), especially for suspensions containing multivalent ions 18 , 53 . Here our current results further confirm its limitation.…”
Section: Resultsmentioning
confidence: 99%
“…The classical Derjaguin-Landau-Verwey-Overbeek (DLVO) model is widely used to simulate the aggregation behavior of soil colloids in different electrolytes 12 – 14 . In general, divalent cations (Mg 2+ and Ca 2+ ) destabilize soil colloid particles more efficiently than monovalent cations (K + and Na + ) due to a more intensely compressed electrical double layer (EDL), the Schulze-Hardy rule and DLVO theory can be used to explain it 15 – 18 . However, divalent ions have different surface affinities, leading to a different aggregation process 19 .…”
The variable role and fate of soil colloids under different environmental conditions are derived from their dispersion and aggregation properties. In this work, dynamic and static light scattering were used to characterize the original size, aggregation kinetics of natural black soil colloids (BSCs) and structural features of aggregates in electrolytes with different cations (K+, Mg2+, Ca2+), respectively. For these three cations, the aggregation kinetics followed the trend of Ca2+ > Mg2+ > K+ and the critical coagulation concentration (CCC) followed the sequence: K+ (134.30 mmol L−1) > Mg2+ (13.27 mmol L−1) > Ca2+ (4.19 mmol L−1). The results indicated that the aggregation behavior in different valence cation systems followed the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) model qualitatively. However, the quantitative differences of CCC suggest the existence of ion-specific effects. The effective ionic charge coefficient 1.31, 2.20, and 2.78 of K+, Mg2+ and Ca2+ were proposed to consider of all the non-DLVO factors, which were obtained by forming a relationship based on mathematic between the electrostatic repulsion and the van der Waals attractive interaction at the CCC. The non-classical polarization of cations in a strong soil electric field is a primary mechanism of cation effects on soil colloid interactions, causing the difference in colloid interaction energy and further affecting soil colloid aggregation. This result is crucial for enriching the theory of charged colloidal interactions.
“…Compared with monovalent cations, a much lower concentration of divalent cations induced a drastic BSC aggregation, which may be because high-valent cations can make the surface charge of BSCs less negative through the increased charge screening effect, which benefits aggregation 43 . Previous studies have found that the stronger the surface charge, the more significant the shielding effect of high-valent cations 18 . Figure 2 The average effective hydrodynamic diameters of the BSC particle aggregates changing with the experimental time.…”
Section: Resultsmentioning
confidence: 99%
“…Some scholars define this threshold value at 25 mV and called it 25 mV rule 52 . Later, researchers estimat the CCCs using 25 mV as a threshold of stability, and they found that 25 mV rule is clearly unreliable for low CCCs (< 100 mV), especially for suspensions containing multivalent ions 18 , 53 . Here our current results further confirm its limitation.…”
Section: Resultsmentioning
confidence: 99%
“…The classical Derjaguin-Landau-Verwey-Overbeek (DLVO) model is widely used to simulate the aggregation behavior of soil colloids in different electrolytes 12 – 14 . In general, divalent cations (Mg 2+ and Ca 2+ ) destabilize soil colloid particles more efficiently than monovalent cations (K + and Na + ) due to a more intensely compressed electrical double layer (EDL), the Schulze-Hardy rule and DLVO theory can be used to explain it 15 – 18 . However, divalent ions have different surface affinities, leading to a different aggregation process 19 .…”
The variable role and fate of soil colloids under different environmental conditions are derived from their dispersion and aggregation properties. In this work, dynamic and static light scattering were used to characterize the original size, aggregation kinetics of natural black soil colloids (BSCs) and structural features of aggregates in electrolytes with different cations (K+, Mg2+, Ca2+), respectively. For these three cations, the aggregation kinetics followed the trend of Ca2+ > Mg2+ > K+ and the critical coagulation concentration (CCC) followed the sequence: K+ (134.30 mmol L−1) > Mg2+ (13.27 mmol L−1) > Ca2+ (4.19 mmol L−1). The results indicated that the aggregation behavior in different valence cation systems followed the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) model qualitatively. However, the quantitative differences of CCC suggest the existence of ion-specific effects. The effective ionic charge coefficient 1.31, 2.20, and 2.78 of K+, Mg2+ and Ca2+ were proposed to consider of all the non-DLVO factors, which were obtained by forming a relationship based on mathematic between the electrostatic repulsion and the van der Waals attractive interaction at the CCC. The non-classical polarization of cations in a strong soil electric field is a primary mechanism of cation effects on soil colloid interactions, causing the difference in colloid interaction energy and further affecting soil colloid aggregation. This result is crucial for enriching the theory of charged colloidal interactions.
“…BNNSs were synthesized by chemical vapor deposition using B(OMe) 3 as the B source and NH 3 gas as the N source, as described elsewhere. 43 Ionic strength was adjusted by analytical grade NaCl purchased from VWR. PEI B was bought from Alfa Aesar (M w = 10 000 g/mol) and PEI L (M w = 5000 g/mol) and PLL (M w = 15 000 g/mol) of analytical grade from Sigma-Aldrich and were used as received.…”
Boron nitride nanospheres
(BNNSs) were functionalized with polyelectrolytes.
The effect of the polyelectrolyte dose and ionic strength on the charging
and aggregation properties was investigated. At appropriate polyelectrolyte
doses, charge neutralization occurred, whereas by increasing the dose,
charge reversal was observed. The complete coating of the particles
was indicated by a plateau in the ζ-potential values, which
do not change significantly beyond the dose corresponding to the onset
of such a plateau. The dispersions were highly aggregated around the
charge neutralization point, while at lower or higher doses, the particles
were stable. The salt-induced aggregation experiments revealed that
the polyelectrolyte coatings contribute to the colloidal stability
of the particles, namely, the critical coagulation concentrations
deviated from the one determined for bare BNNSs. The presence of electrostatic
and steric interparticle forces induced by the adsorbed polyelectrolyte
chains was assumed. The obtained results confirm that the comprehensive
investigation of the colloidal stability of BNNS particles is crucial
to design stable or unstable dispersions and that polyelectrolytes
are suitable agents for both stabilization and destabilization of
BNNS dispersions, depending on the purpose of their application.
“…Accordingly, slow aggregation occurs at low IL concentrations and with increasing CCC values reported earlier for colloidal particles in the presence of various monovalent inorganic coions showed no clear dependence on the type of coions. 47,67 However, when ILs were involved in the systematic study, the aggregation features were sensitive to the type of coion, 31 due to shortrange attraction between the IL constituents, as revealed in direct force measurements. 30…”
The influence of ionic liquid (IL) anions and cations on the charging and aggregation properties of layered double hydroxide (LDH) nanoparticles was systematically studied. Surface charge characteristics were explored in...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
