Extraction of Alumina from Local Clays by Hydrochloric Acid Process@@@إنتاج الألومينا من الطفلة الوطنية بالمعالجة بحامض الأيدروكلوريك
A bench work study was carried out to investigate the use of kaolinitic clay containing 29.4% Al2O3 extremely abundant in Saudi Arabia for the production of pure alumina by calcination at 700 o C for 1h (recommended by previous investigators) then leached by hydrochloric acid. The effects of leaching temperature (25 o C to boiling temperature), period of activation (10-150 minutes), acid concentration (1M – 6M), particle size (–8 to –200 standard Tyler screen mesh), acid to clay weight ratio (4:1 to 15 : 1ml acid/gm clay) on alumina extraction were investigated. The recommended leaching conditions are: 6 molar for acid concentration at boiling conditions under reflux, one hour for leaching time, –100 mesh standard Tyler screens for particle size of calcined clay and 10 ml acid/gm clay for acid to clay weight ratio. Leaching this local clay sample under these conditions resulted in 32% alumina extraction. Local kaolinitic clay were calcined at temperatures varying between 400 o C and 800 o C at different calcination periods (5 to 120 minutes). The calcined clay was then leached with 3M HCl acid under the above-recommended leaching conditions. The optimum calcination conditions were 600 o C and 1 hour for calcination temperature and time period, respectively. The corresponding alumina extraction from local clay sample is about 63%.
Extraction kinetics of alunite in sulfuric acid and hydrochloric acid
Abstract Extraction kinetics of alunite in sulfuric acid and hydrochloric acid were studied in a batch reactor. The effects of reaction temperature, acid concentration, particle size, calcination temperature, calcination time and KF/Al 2 O 3 molar ratio on the extraction process were investigated. Experimental studies were carried out in the ranges of 35–95 °C for reaction temperature, 0.25–3.0 M for sulfuric acid, 0.5–0.6 M for hydrochloric acid, 76–182 μm for average particle size, 100–900 °C for calcination temperature, 15–60 min for calcination time and 0.15–0.90 for KF/Al 2 O 3 molar ratio. The calcination temperature was the most important parameter affecting the extraction process followed by reaction temperature, particle size and acid concentration. Others had less effect. It was determined that the extraction process is controlled by diffusion through a product layer. The activation energies of the processes were found to be 19.1 and 18.5 kJ/mol for sulfuric acid and hydrochloric acid, respectively. The apparent rate constants were similar for both acids and found to be a function of acid concentration as C 0.33 and particle size r −0.8 .
Study on essential drug use status and its influencing factors among cerebral infarction inpatients in county level hospitals of Anhui Province, China
Background and purpose Drug costs is one of the main components of hospitalization expenditure for cerebral infarction inpatients. In China, the National Essential Medicine System (NEMS) was created to relieve the heavy drug-cost burden for patients. The objective of this study was to investigate essential drug-use status and its influencing factors among cerebral infarction inpatients in county-level hospitals of Anhui province, China. Methods Three county-level hospitals were selected through a multi-stage cluster random sampling method. The hospitalization cost data of cerebral infarction inpatients in the three hospitals were extracted from the Anhui provincial information platform of the New Rural Cooperative Insurance System (NCMS), and whether the proportion of essential drug cost in the total drug cost reached the median value of 33.05% which was set as the evaluation index for essential drug-use status. Questionnaires for hospitals and physicians were designed and given to them to assess influencing factors. Results We retrieved the cost data of 2,189 inpatients from the NCMS platform and investigated 51 corresponding physicians in total. The drug costs accounted for 52.6% of the total hospitalization cost, and essential drug costs alone accounted for 37.0% of the total drug costs. The essential drug-cost proportion was high among physicians with a higher recognition degree on NEMS, older age, lower final academic degree, longer work experience and lower professional title. Married physicians and those with tight organizational affiliation also prescribed more essential drugs. Conclusions Increasing the proportion of essential drugs was an effective way to reduce the disease burden for cerebral infarction patients. Perfecting the NEMS, increasing government investment, reinforcing education and propaganda, and formulating relevant incentive and restrictive mechanisms were all effective ways to promote and increase the number of essential drug prescriptions written by physicians.