DFT Studies on the Water-Assisted Synergistic Proton Dissociation Mechanism for the Spontaneous Hydrolysis Reaction of Al³⁺ in Aqueous Solution

The kinetic mechanism of spontaneous aluminum ion (Al³⁺) hydrolysis reaction in aqueous solution is investigated using the density functional theory–quantum chemical cluster model method. Three typical reaction pathways for the spontaneous Al³⁺ hydrolysis reaction are modeled, including (1) the traditional spontaneous proton dissociation on the Al³⁺ inner-shell coordinated waters; (2) the conventional bulk water-assisted proton dissociation; and (3) the second-shell water-assisted synergistic dissociation of the protons on the Al³⁺ inner-shell waters. The results show that the electrostatic effects between Al³⁺ and its coordinated waters alone cannot fully account for the proton loss on an inner-shell coordinated water. It is suggested that the main reaction pathway for natural hydrolysis of aqueous Al³⁺ is the second-shell water-assisted synergistic proton dissociation, in which the participation of the second hydration shell is crucially important. The calculated synergistic proton dissociation rate constant, <i>k</i>_H⁺ = 1.14 × 10⁵ s^–1, is in close agreement with the experimental results (1.09 × 10⁵ s^–1 and 7.9 × 10⁴ s^–1). The first hydrolysis equilibrium constant p<i>K</i>_a1 of Al³⁺ is calculated as 5.82, also consistent with the literature value of 5.00. This work elucidates the molecular mechanism of the spontaneous Al³⁺ hydrolysis reaction in natural waters and has important environmental implications

Theoretical Studies of the Formation Mechanisms, Thermodynamic Stabilities, and Water-Exchange Reactivities of Aluminum-Salicylate Complexes in Aqueous Solution

The formation mechanisms, thermodynamic stabilities, and water-exchange reactivities of 1:1 monomer aluminum–salicylate (Al–salicylate) complexes in acidic aqueous solution are investigated using the density functional theory-quantum chemical cluster model (DFT-CM) method. (1) The formation pathways for possible monodentate and bidentate Al–salicylate configurations are modeled with the gas phase-supermolecule-polarizable continuum model (GP-SM-PCM). It shows that the formation pathways for the Al–salicylate complexes follow the Eigen-Wilkins mechanism, where the dissociation of an inner-shell coordinated water of Al³⁺ is the rate-determining step. (2) The formation constants <i>K</i>_aq for different Al–salicylate configurations are estimated based on the total Gibbs free energy changes Δ<i>G</i>° for their overall formation pathways. It is indicated that in the acidic aqueous solution at pH ∼ 3, the main existence form of the 1:1 monomer Al–salicylate complex is the phenol-deprotonated bidentate Al­(Sal)­(H₂O)₄⁺ with six-membered ring. Its log <i>K</i>_aq is calculated as 13.8, in good agreement with the literature values of 12.9–14.5. (3) The water-exchange reactions are modeled for different Al–salicylate configurations. The water-exchange rate constant for Al­(Sal)­(H₂O)₄⁺ is estimated as log <i>k</i>_H2O = 3.9 s^–1, close to the experimental value of 3.7 s^–1. It proves again that this configuration is the dominant form under experimental conditions

Additional file 1 of Community-embedded follow-up management intervention for geriatric primary care: a mixed-methods study of an integrated health services model

Supplementary Material

S1 Data -

Widespread vaccination against important diseases plays a key role for global health security, particularly in the context of the COVID-19 pandemic. However, building and maintaining trust in immunization services remains challenging because of doubts about quality and safety of vaccines. China has periodically faced mounting pressure and even public outrage triggered by incidents of poor-quality vaccines. We aimed to evaluate the impact of the diphtheria, pertussis, and tetanus (DPT) vaccine scandal of 2018 in China and the ensuing misinformation on vaccination, and investigate differential responses to the scandal by ethnic and socioeconomic factors. With data from January 2017 to December 2018 in Sichuan province, China, we used a difference-in-differences (DID) method to compare the changes in the county-level monthly DPT vaccinations against the hepatitis B vaccinations, both before and after the DPT vaccine scandal. We found that the number of DPT vaccinations decreased by 14.0 percent in response to the vaccine scandal and ensuing misinformation. The number of vaccinations in minority regions, under-developed regions, and regions with poor medical resources decreased more than in non-minority regions, developed regions, and regions with good medical resources (24.5 versus 10.1 percent, 17.3 versus 8.3 percent, and 17.0 versus 8.7 percent, respectively). People did more online searching for “Substandard vaccine” and “DPT vaccine” after the scandal, with the socioeconomically advantaged group searching more compared with the socioeconomically disadvantaged group. The results suggest the urgent need to make true information about the vaccine easily accessible over the internet, especially for the socioeconomically disadvantaged groups. Our findings for China can also have implications for immunization service planning for better safeguarding public health in other countries, particularly developing ones.</div

Parallel trends assumption check for number of vaccinations.

Parallel trends assumption check for number of vaccinations.</p

Changes in number of vaccinations in response to the vaccine scandal and ethical and socioeconomic subsample analysis.

Changes in number of vaccinations in response to the vaccine scandal and ethical and socioeconomic subsample analysis.</p

List of impoverished counties in Sichuan.

Widespread vaccination against important diseases plays a key role for global health security, particularly in the context of the COVID-19 pandemic. However, building and maintaining trust in immunization services remains challenging because of doubts about quality and safety of vaccines. China has periodically faced mounting pressure and even public outrage triggered by incidents of poor-quality vaccines. We aimed to evaluate the impact of the diphtheria, pertussis, and tetanus (DPT) vaccine scandal of 2018 in China and the ensuing misinformation on vaccination, and investigate differential responses to the scandal by ethnic and socioeconomic factors. With data from January 2017 to December 2018 in Sichuan province, China, we used a difference-in-differences (DID) method to compare the changes in the county-level monthly DPT vaccinations against the hepatitis B vaccinations, both before and after the DPT vaccine scandal. We found that the number of DPT vaccinations decreased by 14.0 percent in response to the vaccine scandal and ensuing misinformation. The number of vaccinations in minority regions, under-developed regions, and regions with poor medical resources decreased more than in non-minority regions, developed regions, and regions with good medical resources (24.5 versus 10.1 percent, 17.3 versus 8.3 percent, and 17.0 versus 8.7 percent, respectively). People did more online searching for “Substandard vaccine” and “DPT vaccine” after the scandal, with the socioeconomically advantaged group searching more compared with the socioeconomically disadvantaged group. The results suggest the urgent need to make true information about the vaccine easily accessible over the internet, especially for the socioeconomically disadvantaged groups. Our findings for China can also have implications for immunization service planning for better safeguarding public health in other countries, particularly developing ones.</div

Event study analysis for online searches of “Substandard vaccine” and “DPT vaccine”.

Event study analysis for online searches of “Substandard vaccine” and “DPT vaccine”.</p

Baseline estimation and estimation without vaccine supply as control.

Baseline estimation and estimation without vaccine supply as control.</p

Estimation for impoverished and non-impoverished counties.

Estimation for impoverished and non-impoverished counties.</p