Microplastics in retail shellfish from a seafood market in eastern Thailand: Occurrence and risks to human food safety.

This study aimed to investigate the presence of microplastics in three economically essential shellfish species: green mussels, cockles and spotted babylon. The average abundance of microplastics ranged from 2.41 to 2.84 particles/g wet weight. The predominant shape was fiber, with colors ranging from black-grey to transparent. The size of the microplastics discovered was <1.0 mm. Polystyrene and polyethylene were the most detected types in mussels and cockles, while linen was the predominant type in spotted babylon. The Thai population's estimated annual intake (EAI) of microplastics through shellfish consumption ranged from 20.23 to 1178.42 particles/person/year. The potential human health risks were evaluated using the polymer hazard index (PHI), which led to risk categories III-IV. These findings, along with others from the literature, indicate that shellfish consumption may pose risks to human health, depending on the species consumed and the origin of the specimens.

Microplastic pollution in surface seawater and beach sand from the shore of Rayong province, Thailand: Distribution, characterization, and ecological risk assessment.

The distribution, characteristics, and ecological risk of microplastics in beach sand and seawater samples collected along the shore of Rayong province, Thailand, were investigated in this study. The average microplastics abundance in beach sand and seawater was 338.89 ± 264.94 particles/kg d.w. and 1781.48 ± 1598.36 particles/m3, respectively. Beach sand and seawater had the most yellow-brown particles and transparent microfibers, respectively. The most common microplastics (100-500 µm) and polyethylene were found. In beach sand, the potential ecological risk (RI) is classified as minor, while in seawater, it is classified as medium. The PLIzone in beach sand and seawater was Hazard Level II and Hazard Level IV, respectively. Despite their apparent proximity, the non-correlation between risk levels in beach sand and seawater may be due to polymer type variations influenced by the different land-based and sea-based sources.

Amino-functionalized mesoporous silica-magnetic graphene oxide nanocomposites as water-dispersible adsorbents for the removal of the oxytetracycline antibiotic from aqueous solutions: adsorption performance, effects of coexisting ions, and natural organic matter.

The amino-functionalized mesoporous silica-magnetic graphene oxide nanocomposite (A-mGO-Si) was synthesized and used for oxytetracycline (OTC) removal from water. Various factors like the effects of initial concentration, contact time, and influence of pH were investigated. Selective adsorption experiments in connection with coexisting ions and dissolved organic matter (DOM) were also investigated. In this study, humic acid (HA) and tannic acid (TA) were representative of both hydrophobic and hydrophilic DOM, respectively. Results indicated that A-mGO-Si had an adsorption ability for OTC that was relatively greater than that of virgin magnetic graphene oxide (mGO), graphene oxide (GO), Fe3O4 particles, and SBA-15 mesoporous silica and also showed a better uptake removal capacity for OTC at low initial concentration in comparison with the other adsorbents. The adsorption behavior of OTC onto A-mGO-Si could be described by the pseudo-second-order kinetic model and the Freundlich isotherm model. The electrostatic interaction has no influence on the OTC absorbed when the OTC is in an aqueous medium in its zwitterion form (3.22 < pH < 7.46). At high pH, the weak π-π EDA interactions and hydrogen bonding may manifest themselves, hence causing a lower adsorption capacity. The main adsorption mechanisms were plausibly activated by H-bonding, and π-π EDA interactions, while the electrostatic interaction (cation-π interaction) might be the minor adsorption mechanism. Addition of individually exogenous ions (Na+, Mg2+, NO-, and CO32-) resulted in a decrease of OTC adsorption due to the emergence of a competitive effect. Considering the presence of HA and TA in mixed solute systems, the DOM was likely to form a stronger interaction system with mGO-Si, thereby resulting in an adsorption level which was more competitive in the process at low aqueous phase concentration of OTC. In contrast to the high aqueous phase, the coexistence of DOM could promote OTC adsorption. The phenomenon may reflect the result that a surface complexation mechanism could achieve in adsorptions.

Adsorption of single and mixed haloacetonitriles on silica-based porous materials: Mechanisms and effects of porous structures.

Adsorption mechanisms and the role of different porous and crystalline structures on the removal of five haloacetonitriles (HANs) over hexagonal mesoporous silica (HMS), titanium substituted mesoporous silica (Ti-HMS), rod-shaped SBA-15 and microporous zeolite NaY were investigated. In addition, the effect of pH on adsorption mechanism and selective adsorption of five HANs individually and in an equimolar mixed solution were evaluated. The results indicated that the intraparticle diffusion rate constants of the mesoporous adsorbents were higher than that of the microporous NaY. In single solute, the order of adsorption preference (highest to lowest) was mono-HANs > di-HANs > tri-HAN. However, in mixed solute, the large molecular weight of the tri-HAN and di-HANs are more easily adsorbed than the smaller molecular weight mono-HANs. Except for SBA-15, the order of adsorption capacities in mixed HANs solute was not different compared to that observed for the single HAN solute, which might be caused by the higher accessibility to the active sites due to larger pore size. The ion-dipole electrostatic interaction was likely to be the main adsorption mechanism, and was favored at high pH values due to the high negative surface charge density of the adsorbent. The molecular structure of the HANs and hydrophilic/hydrophobic nature affected the adsorption capacities and their selective adsorption from mixed solutes.

Removal of haloacetonitriles in aqueous solution through adsolubilization process by polymerizable surfactant-modified mesoporous silica.

To investigate the adsorption properties and mechanisms of haloacetonitriles (HANs), large-pore SBA-15 mesoporous silica (SBA-CHX) was synthesized using cyclohexane as a swelling agent, and the surface was modified with polymerizable gemini surfactant (PG). The structure and textural properties of the synthesized adsorbents were characterized. PG surfactant coverage on the surface and the degree of polymerization were confirmed with FT-IR analysis. Adsorption experiments were performed under batch conditions to evaluate the influence of the contact time, adsorption isotherms, the effect of the pH solution, and the selective adsorption of five haloacetonitriles (HAN(5)) in individual-solute and mixed-solute solutions and surfactant leaching studies. The results indicated that the hydrophobic HANs were efficiently adsorbed onto PG surfactant-modified SBA-CHX. The selective adsorption mechanisms involved a more complex interplay between the organic partition, surface adsorption (i.e., ion-dipole electrostatic interactions) and hydrophobic interaction that depended upon the adsorbent and adsorbate characteristics. An increased degree of halogen substitution in the HAN molecule significantly affected the adsorption capacity and selectivity by the organic partition. Polymerization of the polymerizable surfactant increased the stability of the adsorbed surfactant on the adsorbent surface.

Adsorption characteristics of haloacetonitriles on functionalized silica-based porous materials in aqueous solution.

The effect of the surface functional group on the removal and mechanism of dichloroacetonitrile (DCAN) adsorption over silica-based porous materials was evaluated in comparison with powdered activated carbon (PAC). Hexagonal mesoporous silicate (HMS) was synthesized and functionalized by three different types of organosilanes (3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane and n-octyldimethysilane). Adsorption kinetics and isotherm models were used to determine the adsorption mechanism. The selective adsorption of five haloacetonitriles (HANs) in the single and mixed solute systems was also studied. The experiments revealed that the surface functional groups of the adsorbents largely affected the DCAN adsorption capacities. 3-Mercaptopropyl-grafted HMS had a high DCAN adsorption capacity compared to PAC. The adsorption mechanism is believed to occur via an ion-dipole electrostatic interaction in which water interference is inevitable at low concentrations of DCAN. In addition, the adsorption of DCAN strongly depended on the pH of the solution as this related to the charge density of the adsorbents. The selective adsorption of the five HANs over PAC was not observed, while the molecular structure of different HANs obviously influenced the adsorption capacity and selectivity over 3-mercaptopropyl-grafted HMS.