Influence of Intramuscular Injection Sites on Pharmacokinetics of Amoxicillin in Olive Flounder (Paralichthys olivaceus) and Its Implication for Antibacterial Efficacy.

This study aimed to investigate the effects of different injection sites, including dorsal, cheek, and pectoral fin muscles, on the pharmacological properties of amoxicillin (AMOX) in olive flounder (Paralichthys olivaceus) after a single intramuscular (IM) injection of 40 mg/kg. The AMOX concentration was measured using high-performance liquid chromatography-tandem mass spectrometry, followed by a non-compartmental model analysis. The peak serum concentrations (Cmax) achieved 3 h after dorsal, cheek, and pectoral fin IM injections were 202.79, 203.96, and 229.59 µg/mL, respectively. The area under the concentration-time curve (AUC) was 1697.23, 2006.71, and 1846.61 µg/mL·h, respectively. The terminal half-life (t1/2λZ) was prolonged for cheek and pectoral fin IM injections (10.12 and 10.33 h, respectively) compared to dorsal IM injection (8.89 h). In the pharmacokinetic-pharmacodynamic analysis, a higher T > minimum inhibitory concentration (MIC) and AUC/MIC values were observed after AMOX was injected into the cheek and pectoral fin muscles compared to the dorsal muscle. Muscle residue depletion was below the maximum residue level from day 7 after IM injection at all three sites. These findings suggest that the cheek and pectoral fin sites provide advantages regarding systemic drug exposure and prolonged action compared with the dorsal site.

Evaluating the feasibility of air environment management system for VOCs through 'VOCs specification' of petroleum refining industry.

The chemical industry releases various types of volatile organic compounds (VOCs) into the atmosphere, and the concentration of VOCs emitted from chimneys is regulated worldwide. However, some VOCs such as benzene are highly carcinogenic, while others such as ethylene and propylene may cause secondary air pollution, owing to their high ozone-generating ability. Accordingly, the US EPA(United State, Environment Protect Agency) introduced a fenceline monitoring system that regulates the concentration of VOCs at the boundary of a facility, away from the chimney source. This system was first introduced in the petroleum refining industry, which simultaneously emits benzene, affecting the local community because of its high carcinogenicity, and ethylene, propylene, xylene, and toluene, which have a high photochemical ozone creation potential (POCP). These emissions contribute to air pollution. In Korea, the concentration at the chimney is regulated; however, the concentration at the plant boundary is not considered. In accordance with the EPA regulations, Korea's petroleum refining industries were identified and the limitations of the Clean Air Conservation Act were studied. The average concentration of benzene at the research facility examined in this study was 8.53 µg/m3, which complied with the benzene action level of 9 µg/m3. However, this value was exceeded at some points along the fenceline, in proximity to the benzene-toluene-xylene (BTX) manufacturing process. The composition ratios of toluene and xylene were 27% and 16%, respectively, which were higher than those of ethylene or propylene. These results suggest that reduction measures in the BTX manufacturing process are necessary. This study shows that legal regulations should enforce reduction measures through continuous monitoring at the fenceline of petroleum refineries in Korea.Implications: Although volatile organic compounds(VOCs) are essential in various industrial sites, they adversely affect the health of people in the near community. Benzene is highly carcinogenic, so it is dangerous if exposed continuously. In addition, there are various types of VOCs, which combine with atmospheric ozone to generate smog. Globally, VOCs are managed as Total VOCs. However, through this study, VOCs have priority, and in the case of the petroleum refining industry, it is suggested that VOCs should be preemptively measured and analyzed to be regulated. In addition, it is necessary to minimize the impact on the local community by regulating the concentration at the fenceline beyond the chimney measurement.

First Report of Enterocytozoon hepatopenaei Infection in Giant Freshwater Prawn (Macrobrachium rosenbergii de Man) Cultured in the Republic of Korea.

In the Republic of Korea, Enterocytozoon hepatopenaei (EHP) was first isolated from Pacific whiteleg shrimp in April 2020; however, there are no existing reports of EHP infection in other shrimp or prawns. Here, we aimed to investigate EHP infection and its prevalence in giant freshwater prawn farms in the Republic of Korea. We tested prawns from 22 farms for EHP infection, and samples from eight farms showed positive EHP infection results in 2021. In EHP-infected prawn farms, the prevalence ranged from 4.9% to 18.2%. The prevalence of EHP infection in the Republic of Korea, derived from the prevalence in prawn farms, was estimated to be 0.8% in 2021. The proliferation of EHP was observed within the hepatopancreatic epithelial cells of prawns using H&E and Giemsa staining. Mature EHP was observed in the sinus between epithelial cells of the digestive tubules. Phylogenetic analysis revealed a clade distinct from the previously reported EHP in Pacific whiteleg shrimps. This is the first report of EHP infection in a giant freshwater prawn in the Republic of Korea, where the prevalence of EHP infection is not high, but it is recognized as an emerging disease that requires periodic monitoring and quarantine management in giant freshwater prawns.

Changes in Risk in Medium Business Plating and Paint Manufacturing Plants following the Revision of the Korean Chemical Accident Prevention System.

Chemical accidents can occur anywhere. The need for chemical management in Korea was realized following the 2012 Gumi hydrofluoric acid accident in 2012. The Chemicals Control Act was enacted in 2015. This system evaluates the risks (high, medium, low) and consequent safety management at all plants that handle hazardous chemical substances. However, the system was criticized as excessive when most plants were designated high-risk without considering their size. Thus, laboratories and hospitals handling very small quantities were subject to regulation. Accordingly, in 2021 Korea revised the system to include off-site consequence analyses and a Korean-style risk analysis. Plants handling very small quantities, such as laboratories and hospitals, were exempt from regulation. In this study, changes in risk were examined for four medium-sized plating and paint manufacturing plants. Under the previous system, all four factories were judged as high-risk groups. In particular, the paint manufacturing plant A, which has an underground storage tank, received a medium risk like the plating plant C, although the possibility of a chemical accident was lower than that of other plants. However, in the changed system, all plants were changed to the low-risk group. In the Korean-style risk analysis, it is possible to see at a glance what is lacking in the plants, such as cooperation between local residents and local governments and the construction of safety facilities according to the type of accident scenario. The revised system is a reasonable regulation for medium business plants.

Optimization of a Cryopreservation Method for the Endangered Korean Species Pogostemon yatabeanus Using a Systematic Approach: The Key Role of Ammonium and Growth Regulators.

Cryopreservation provides a secure long-term conservation option for rare and endangered plant species with non-orthodox or limitedly available seeds. Wide application of cryopreservation to biobank wild flora is hampered by the need to re-optimize nearly all protocol steps for every new species. We applied a systematic approach to simplify optimization of a multi-stage droplet-vitrification method for the endangered wetland Korean species, Pogostemon yatabeanus. This approach consisted of a standard procedure pre-selected based on material type and size, which was complemented with 11 additional treatments to reveal the most impactful conditions. Effect of ammonium nitrate at various protocol steps was also tested. The highest shoot tip survival (92%) and plant regeneration (90%) after cryopreservation were achieved using preculture with 10% sucrose followed by 40 min osmoprotection and 60 min treatment with vitrification solution A3-80% (33.3% glycerol + 13.3% dimethyl sulfoxide + 13.3% ethylene glycol + 20.1% sucrose) on ice. A three-step regrowth procedure starting with ammonium-free medium with 1 mg/L GA3 and 1 mg/L BA followed by ammonium-containing medium with and without growth regulators was essential for the development of healthy plants from cryopreserved shoot tips. This approach enables fast optimization of the cryopreservation procedure for new osmotic stress-sensitive plant species.

Feasibility Evaluation of Designated Quantities for Chemicals Requiring Preparation for Accidents in the Korean Chemical Accident Prevention System.

To prevent chemical accidents, the United States (US), the European Union (EU), and the Republic of Korea operate legal systems, such as risk management plans (RMP) and process safety management (PSM), to prevent chemical accidents inside and outside the workplace. The duty to implement chemical accident prevention systems and the criteria for being a target workplace are dependent on the designated quantities of chemicals handled. A chemical accident prevention system is obligatory for storage and handling of legally declared chemicals in the workplace. Benzene, toluene, xylene, methyl ethyl ketone, and ethyl acetate are all flammable materials that are commonly used as solvents in the chemical industry. These substances are grouped into flammable substances groups in the US and the EU, and are managed with the same designated quantities. However, in Korea, the designated quantities are: benzene, 10,000 kg; toluene, xylene, and methyl ethyl ketone, 200,000 kg; and ethyl acetate, 20,000 kg. In order to evaluate the validity of the chemical quantities, fire explosion scenarios during chemical accidents were modeled using two modeling programs, Areal Location of Hazardous Atmosphere (ALOHA) and Korea Off-Site Risk Assessment Supporting Tool (KORA) software, under the same conditions. Similar damage radii were found for the five flammable materials with both pool fires and vapor cloud explosions (VCE). Based on these damage radii, the designated quantities of five substances were calculated and included in the range (10,000 to 13,500 kg). The results show that current designated quantities underestimate chemical substances, and for the prevention of accidents and post-management after chemical accidents, it is necessary to manage flammable substances under one grouping.

Valuation of Estimation Toxic Chemical Release Inventory Method-Focusing on Paint Manufacturing Process.

Industrial chemicals differ in their treatment methods and types, depending on their physicochemical properties. Highly volatile chemicals are emitted despite installation of preventive facilities, such as scrubbers and adsorption towers. Some countries release a Toxic Release Inventory (TRI), which is a mandatory report on the amount of chemicals emitted annually. This report is released to the citizens to ensure their right to knowledge and life. Numerous methods have been devised to investigate the amount of chemical emissions. There are four methods to estimate TRI emissions (Emission Factor Method; Material Balance Method; Source Testing Method; Emission Model Method). Moreover, efforts have been made to increase awareness and formulate plans to reduce chemical emissions. Despite this, the TRI method tends to underestimate and overestimate, especially due to volatile compounds. If the results of the TRI emissions are underestimated, toxic chemicals can have a negative impact on citizens. Volatile compounds are commonly used in chemical manufacturing plants, such as paint plants. In this study, a suitable method for each industrial process was suggested based on conservative estimates of multiple toxic chemical inventory method, focusing on the paint manufacturing process. In the paint manufacturing plant, storage, weighing, and mixing processes should be used emission model method to estimate TRI. In the reaction process, TRI must be estimated by the source test method. In the transfer process, the emission factor method should be used to estimate TRI. In the atmosphere prevention process, the emission factor method or source testing method should be used depending on the physical and chemical properties such as vapor pressure of the chemical.

Flammable Substances in Korea Considering the Domino Effect: Assessment of Safety Distance.

Benzene, toluene, and xylene (BTX) are flammable substances used in a wide range of raw materials and products. Chemical accidents caused by flammable substances are different from leakage accidents of toxic materials. Initial explosions and fires may cause secondary or tertiary explosions, or fires with nearby flammable materials. This is called the domino effect. In cases of leakage accidents, it is possible to prevent accidents through early control of the leakage to the outside or by bypassing, but it is difficult to cope with explosions because they occur instantaneously. To prevent explosions due to the domino effect, a safety distance must be set. Safety distances vary widely by country. In the case of the United States (US) or the European Union (EU), safety distances are set in various ways depending on the chemical industry and the amount of flammable substances being handled. However, countries such as Korea, Taiwan, and Dubai have comprehensive regulation, and the safety distances are small. In this study, we simulated the range of overpressure at which other chemical equipment could explode when an explosion occurs in a flammable BTX storage tank. There are three types of analysis methods of vapor cloud explosion. PHAST (Process Hazard Analysis Software Tool) and ALOHA (Areal Location of Hazardous Atmosphere) were selected to model explosions using three methods (trinitrotoluene equivalence method, the Netherlands Organization multi-energy method, and Baker-Strehlow-Tang method). The results indicated that the safety distances in the US and EU showed low probability of a domino effect, but those in Korea, Dubai, and Taiwan could lead to a secondary explosions. Therefore, it is necessary to propose a reasonable method to determine safety distances considering the amount and physicochemical characteristics of the flammable substances being used.

Suitability Assessment of Legal Regulation of Chemical Concentrations According to Vapor Pressure and Damage Radius.

Many chemicals used in the industrial field present risks, which differ depending on their chemical properties. Additionally, their various physicochemical properties change considerably with concentration. Many chemicals are used in customized processes in factories in the form of different aqueous solutions. The Korean Chemicals Control Act evaluates "hazardous chemicals," describes their risks to the public, and regulates their concentration. To prepare against chemical accidents, factories construct models of potential damage radius, which is greatly influenced by a chemical's vapor pressure. This study selected substances with widely varying vapor pressures (hydrogen fluoride, hydrogen chloride, aqueous ammonia, and hydrogen peroxide) and compared the results of different modeling programs (KORA, ALOHA, PHAST, and RMP*Comp) for various aqueous solution concentrations. The results showed that damage radius and vapor pressure increased similarly for each substance. Damage radius was negligible at low concentrations for all substances studied. Damage radius of ammonia solution increased with vapor pressure. Hydrogen fluoride is not found in aqueous solution at concentrations of less than 37%, and hydrogen peroxide does not show a large damage radius at low concentrations. However, the Chemicals Control Act strictly regulates hydrogen fluoride concentration beginning at 1%, hydrogen chloride and aqueous ammonia at 10%, and hydrogen peroxide at 6%. To effectively prepare against chemical accidents, we must examine scientifically-based, suitable regulations based on physicochemical properties.

Alternative Risk Assessment for Dangerous Chemicals in South Korea Regulation: Comparing Three Modeling Programs.

Unlike other countries, the Korean chemical industry does not clearly distinguish between industrial sites and residential areas. The 2012 Gumi Hydrogen Fluoride Accident revealed that chemical accidents could cause damage to nearby residents. Accordingly, the Chemicals Control Act was enacted in 2015, which requested industrial sites using chemicals to perform a risk assessment for all chemical facilities and to distribute the results to the local residents and governments. Industrial businesses had the responsibility of warning the local residents. In this study, two programs (Areal Location of Hazardous Atmospheres (ALOHA), Process Hazard Analysis Software Tool (PHAST)) were compared with Korea Off-site Risk Assessment Supporting Tool (KORA), which is the current representative risk assessment program used in Korea Chemicals Control Act. The five chemical substances (nitric acid, hydrogen chloride, ammonia, sulfuric acid, and formaldehyde) most commonly involved in chemical accidents were selected. The range of influence of ERPG-2 (Emergency Response Planning Guideline) on chemical accidents was modeled and the results compared. ALOHA was found to be the most suitable program for the determination of toxicity for nitrate acid and ammonia, KORA for hydrogen chloride and sulfuric acid, and PHAST for formaldehyde. To maximize the safety of many local residents and to prepare for chemical accidents, risk assessments should be conducted using a variety of risk assessment programs, and the worst-case damage radius should be determined.

Antioxidant effects of Geranium nepalense ethanol extract on H2O2-induced cytotoxicity in H9c2, SH-SY5Y, BEAS-2B, and HEK293.

Oxidative damage leads to many diseases. In this study, we evaluated the antioxidant effects of 70% ethanol extract of Geranium nepalense (GNE) on hydrogen peroxide-induced cytotoxicity in cell lines: H9c2, SH-SY5Y, HEK293, and BEAS-2B. We determined the free radical scavenging activity of GNE using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), and superoxide dismutase-like activities, as well as the polyphenol and flavonoid contents of GNE. The results showed that GNE scavenged DPPH and ABTS radicals in a dose-dependent manner. In addition, it contained abundant contents of total polyphenol and flavonoid contents and strongly suppressed cellular reactive oxygen species, thereby protecting H2O2-induced cytotoxicity in H9c2, SH-SY5Y, HEK293, and BEAS-2B cell lines. The powerful antioxidant activity exhibited by GNE, both in vitro and in cell systems, was attributed to its free radical scavenging activity. Therefore, GNE may be useful in preventing oxidative stress-induced diseases including Alzheimer's disease, respiratory inflammatory disease, and chronic kidney diseases.

Clinical Significance of Repetitive Compound Muscle Action Potentials in Patients with Myasthenia Gravis: A Predictor for Cholinergic Side Effects of Acetylcholinesterase Inhibitors.

BACKGROUND AND PURPOSE: Acetylcholinesterase inhibitors (AChEIs) are widely used to treat myasthenia gravis (MG). Although AChEIs are usually tolerated well, some MG patients suffer from side effects. Furthermore, a small proportion of MG patients show cholinergic hypersensitivity and cannot tolerate AChEIs. Because repetitive compound muscle action potentials (R-CMAPs) are an electrophysiologic feature of cholinergic neuromuscular hyperactivity, we investigated the clinical characteristics of MG patients with R-CMAPs to identify their clinical usefulness in therapeutic decision-making. METHODS: We retrospectively reviewed the clinical records and electrodiagnostic findings of MG patients who underwent electrodiagnostic studies and diagnostic neostigmine testing (NT). RESULTS: Among 71 MG patients, 9 could not tolerate oral pyridostigmine bromide (PB) and 17 experienced side effects of PB. R-CMAPs developed in 24 patients after NT. The highest daily dose of PB was lower in the patients with R-CMAPs (240 mg/day vs. 480 mg/day, p<0.001). The frequencies of PB intolerance and side effects were higher in the patients with R-CMAPs than in those without R-CMAPs [37.5% vs. 0% (p<0.001) and 45.8% vs. 12.8% (p=0.002), respectively]. The MG Foundation of America postintervention status did not differ significantly between MG patients with and without R-CMAPs, and the response to immunotherapy was also good in both groups. CONCLUSIONS: Side effects of and intolerance to AChEIs are more common in MG patients with R-CMAPs than in those without R-CMAPs. AChEIs should be used carefully in MG patients with R-CMAPs. The presence of R-CMAPs after NT may be a good indicator of the risks of PB side effects and intolerance.

Clinical outcome of patients with refractory Kawasaki disease based on treatment modalities.

PURPOSE: Although a significant number of reports on new therapeutic options for refractory Kawasaki disease (KD) such as steroid, infliximab, or repeated intravenous immunoglobulin (IVIG) are available, their effectiveness in reducing the prevalence of coronary artery lesions (CAL) remains controversial. This study aimed to define the clinical characteristics of patients with refractory KD and to assess the effects of adjuvant therapy on patient outcomes. METHODS: We performed a retrospective study of 38 refractory KD patients from January 2012 to March 2015. We divided these patients into 2 groups: group 1 received more than 3 IVIG administration+ steroid therapy, (n=7, 18.4%), and group 2 patients were unresponsive to initial IVIG and required steroid therapy or second IVIG (n=31, 81.6%). We compared the clinical manifestations, laboratory results, and echocardiographic findings between the groups and examined the clinical utility of additional therapies in both groups. RESULTS: A significant difference was found in the total duration of fever between the groups (13.0±4.04 days in group 1 vs. 8.87±2.30 days in group 2; P=0.035). At the end of the follow-up, all cases in group 1 showed suppressed CAL. In group 2, coronary artery aneurysm occurred in 2 patients (6.4 %). All the patients treated with intravenous corticosteroids without additional IVIG developed CALs including coronary artery aneurysms. CONCLUSION: No statistical difference was found in the development of CAL between the groups. Prospective, randomized, clinical studies are needed to elucidate the effects of adjunctive therapy in refractory KD patients.

Whole-Body Muscle MRI in Patients with Hyperkalemic Periodic Paralysis Carrying the SCN4A Mutation T704M: Evidence for Chronic Progressive Myopathy with Selective Muscle Involvement.

BACKGROUND AND PURPOSE: Hyperkalemic periodic paralysis (hyperKPP) is a muscle sodium-ion channelopathy characterized by recurrent paralytic attacks. A proportion of affected individuals develop fixed or chronic progressive weakness that results in significant disability. However, little is known about the pathology of hyperKPP-induced fixed weakness, including the pattern of muscle involvement. The aim of this study was to characterize the patterns of muscle involvement in hyperKPP by whole-body magnetic resonance imaging (MRI). METHODS: We performed whole-body muscle MRI in seven hyperKPP patients carrying the T704M mutation in the SCN4A skeletal sodium-channel gene. Muscle fat infiltration, suggestive of chronic progressive myopathy, was analyzed qualitatively using a grading system and was quantified by the two-point Dixon technique. RESULTS: Whole-body muscle MRI analysis revealed muscle atrophy and fatty infiltration in hyperKPP patients, especially in older individuals. Muscle involvement followed a selective pattern, primarily affecting the posterior compartment of the lower leg and anterior thigh muscles. The muscle fat fraction increased with patient age in the anterior thigh (r=0.669, p=0.009), in the deep posterior compartment of the lower leg (r=0.617, p=0.019), and in the superficial posterior compartment of the lower leg (r=0.777, p=0.001). CONCLUSIONS: Our whole-body muscle MRI findings provide evidence for chronic progressive myopathy in hyperKPP patients. The reported data suggest that a selective pattern of muscle involvement-affecting the posterior compartment of the lower leg and the anterior thigh-is characteristic of chronic progressive myopathy in hyperKPP.

Predictive factors for myasthenic crisis after videoscopic thymectomy in patients with myasthenia gravis.

INTRODUCTION: Predictive factors for myasthenic crisis after transsternal thymectomy have been reported, but little is known about myasthenic crisis after videoscopic thymectomy (MCAVT). METHODS: We investigated 146 myasthenia gravis patients who underwent videoscopic thymectomy. RESULTS: Patients with MCAVT had a lower forced vital capacity (FVC) (2.1 vs. 3.0 L, P < 0.001) than those without. Low-frequency repetitive nerve stimulation showed decremental responses of the orbicularis oculi (47.1% vs. 18.1%, P = 0.001) and nasalis muscles (54.1% vs. 21.4%, P < 0.001), which were more pronounced in patients with MCAVT than those without. According to multivariate analysis, FVC (OR 0.144, 95% confidence interval [CI], 0.044-0.479, P = 0.002) and decremental response of orbicularis oculi (odds ratio, 1.029; 95% CI, 1.001-1.058, P = 0.044) were independently associated with MCAVT. CONCLUSIONS: FVC and decremental response of orbicularis oculi were associated with MCAVT.

Clinical and Electrophysiologic Responses to Acetylcholinesterase Inhibitors in MuSK-Antibody-Positive Myasthenia Gravis: Evidence for Cholinergic Neuromuscular Hyperactivity.

BACKGROUND AND PURPOSE: Patients with muscle-specific tyrosine kinase (MuSK) antibody (MuSK-Ab)-positive myasthenia gravis (MG) show distinct responses to acetylcholinesterase inhibitors (AChEIs). Although clinical responses to AChEIs in MuSK-Ab MG are reasonably well known, little is known about the electrophysiologic responses to AChEIs. We therefore investigated the clinical and electrophysiologic responses to AChEIs in MuSK-Ab-positive MG patients. METHODS: We retrospectively reviewed the medical records and electrodiagnostic findings of 17 MG patients (10 MuSK-Ab-positive and 7 MuSK-Ab-negative patients) who underwent electrodiagnostic testing before and after a neostigmine test (NT). RESULTS: The frequency of intolerance to pyridostigmine bromide (PB) was higher in MuSK-Ab-positive patients than in MuSK-Ab-negative patients (50% vs. 0%, respectively; p=0.044), while the maximum tolerable dose of PB was lower in the former (90 mg/day vs. 480 mg/day, p=0.023). The frequency of positive NT results was significantly lower in MuSK-Ab-positive patients than in MuSK-Ab-negative patients (40% vs. 100%, p=0.035), while the nicotinic side effects of neostigmine were more frequent in the former (80% vs. 14.3%, p=0.015). Repetitive compound muscle action potentials (R-CMAPs) developed more frequently after NT in MuSK-Ab-positive patients than in MuSK-Ab-negative patients (90% vs. 14.3%, p=0.004). The frequency of a high-frequency-stimulation-induced decrement-increment pattern (DIP) was higher in MuSK-Ab-positive patients than in MuSK-Ab-negative patients (100% vs. 17.7%, p=0.003). CONCLUSIONS: These results suggest that MuSK-Ab-positive MG patients exhibit unique and hyperactive responses to AChEIs. Furthermore, R-CMAP and DIP development on a standard AChEI dose may be a distinct neurophysiologic feature indicative of MuSK-Ab-positive MG.

Molluscum contagiosum as a skin manifestation of immune reconstitution inflammatory syndrome in an AIDS patient who is receiving HAART.

Highly active antiretroviral therapy (HAART), which restores specific immune responses, may paradoxically cause an inflammatory reaction known as immune reconstitution inflammatory syndrome (IRIS). We report a patient with acquired immune deficiency syndrome, who presented Molluscum contagiosum as IRIS after HAART, the first case in Korea.

Phosphate uptake by TiO2: batch studies and NMR spectroscopic evidence for multisite adsorption.

Systematic studies, combining batch experiments with NMR spectroscopic methods, are carried out for phosphate sorption on titanium dioxide (TiO(2)). It is found that phosphate sorption on TiO(2) decreases with increasing pH, whereas the phosphate uptake by TiO(2) increases with increasing ionic strength of the solution. In I ≤ 0.1 M, the sorption sharply increases and reaches a near maximum and then followed by little changes showing Langmuir-type behavior, whereas in I = 0.7 M, non-Langmuirian uptake becomes evident as equilibrium phosphate concentrations increase in solution. The sorption of phosphate on TiO(2) is rapid and mostly irreversible at pH 4.5 and 7.0. At pH 9.0, however, the phosphate sorption is initially reversible and followed by resorption of phosphate on TiO(2) at the system re-equilibration. (31)P{(1)H} cross-polarization and magic angle spinning (CP/MAS) NMR spectra contain at least four main peaks which appear similar in position and width under all adsorption conditions, but vary in intensity with surface loading. The spectral characteristics of these peaks, including cross-polarization dynamics and chemical shift anisotropy obtained from spinning sideband analysis, suggest that they arise from distinct inner-sphere adsorption complexes, most of which are protonated. These results indicate that uptake of phosphate by TiO(2) occurs by formation of several types of surface complexes.