A hydrotalcite with Mg/AI molar ratio 2 was prepared by co-precipitation method and was characterized by XRD, TG/DTA, Zeta potential and BET surface area. The hydrotalcite was calcined at 500℃, with the dehydration from interlayer, the dehydroxilation from the brucite-like layer and the decomposition of carbonate successively, transformed into the mixed oxide type. The removal of thiocyanate from aqueous solution by using the original hydrotalcite and calcined hydrotalcite (HTC-500) was investigated. The results showed that the thiocyanate adsorption capacity of calcined hydrotalcite was much higher than that of the original form. Calcined hydrotalcite was particularly effective at removing thiocyanate, and that the effective range of pH for the thiocyanate removal are between 5.5-10.0. The experimental data of thiocyanate removal fit nicely with Langmuir isotherm, and the saturated adsorption uptake was 96.2 mg SCN-/g HTC-500. The adsorption of thiocyanate by calcined hydrotalcite follows first-order kinetics. And the intercalation to the structure recovery for calcined hydrotalcite. But the presence of additional anions could affect the adsorption behavior of thiocyanate. 相似文献
Objective: Alcohol-impaired driving is a significant factor in fatal and serious injury-producing crashes in the United States and many other countries. In 2013, the State of Maryland implemented an anti-driving under the influence (DUI) enforcement program, called the State Police Impaired Driving Reduction Effort (SPIDRE). This enforcement effort consisted of a select team of 7 police officers from the Maryland State Police who engaged in high-intensity driving under the influence (DUI) enforcement. The purpose of this evaluation was to determine the impact of the SPIDRE program on impaired-driving crashes, DUI arrests, DUI adjudicative outcomes, and public perceptions of DUI enforcement.
Methods: Data from alcohol-related crashes, arrests, and adjudicative outcomes of those arrests were used, along with data obtained from public opinion and bar patron surveys, to compare counties where the SPIDRE program operated and non-SPIDRE counties where it did not. The evaluation period extended from 2010 to 2016 in monthly intervals. Autoregressive integrated moving average (ARIMA) methods were used for the data analyses of crashes and arrests.
Results: There was no significant reduction in alcohol-related crashes as reported by the police associated with the SPIDRE program. However, there was a statistically significant decrease in the ratio of single-vehicle nighttime to multiple-vehicle daytime crashes in the SPIDRE counties but not in any other counties, suggesting a positive effect using this surrogate measure of impaired-driving crashes. The specific comparison counties as well as the other non-SPIDRE counties in Maryland experienced a statistically significant decrease in DUI arrests during the evaluation period, whereas the SPIDRE counties did not show such a decrease. Further, the arrests made by the SPIDRE team resulted in a significantly higher rate of positive adjudicative outcomes than arrests made by non-SPIDRE officers in those counties where the SPIDRE team operated. There was no evidence that the public was more aware of DUI enforcement efforts in the SPIDRE counties than in the non-SPIDRE counties.
Conclusions: The SPIDRE program appeared able to prevent a downward trend in DUI arrests, experienced by the rest of the state, and achieved higher quality arrests resulting in more positive adjudicative outcomes. The way in which the SPIDRE team was deployed may have lacked sufficient duration and intensity (e.g., only 2–3 months of activity in any given county) to achieve a reduction in alcohol-impaired-driving crashes as reported by the police. It is recommended that the SPIDRE team increase its enforcement activities for at least 9–12 consecutive months in the county where they are employed. 相似文献