ABSTRACT
Activated alumina (AA) has been extensively applied in the defluorination of industrial wastewaters and groundwater. Although the dissolution of AA due to formation of fluoroaluminate complexes (AlFx3-x), especially in acidic condition, has been observed, its role on fluoride uptake by alumina has not been discussed in any previous literature, most of which consider F- as the sole adsorbed species. The present study described the effect of fluoroaluminate complexes on fluoride adsorption onto alumina. Results indicated that fluoroaluminate complexes, major fluoride species at pHâ¯<â¯6, were responsible for total fluoride adsorbed. Free fluoride ions were adsorbed mainly in the alkaline pH region, e.g., pHâ¯>â¯6. The dissolution of AA during defluorination was measured and analyzed by the thermodynamic solubility model. The surface concentration of F- and AlFx3-x were calculated considering electrostatic interactions. Characterization of fluoride-laden AA by XPS revealed that the fraction of surface Al-F species decreased with pH, which suggested the transition of the surface fluorinated species to that of free fluoride ions. The stability constants of four surface complexes, namely, AlOH-FAl2+, AlOH-F2Al+, AlOH2+-F- and AlOH-F-, were 106.88, 105.36, 102.72 and 102.36, respectively. Obviously fluoroaluminate complexes exhibited stronger chemical bonds with the surface hydroxy species than free fluoride.
ABSTRACT
AIM: To overcome the technical difficulty of exteriorizing a specimen through the descending colon stump, we applied laparoscopic-assisted natural orifice specimen extraction (LA-NOSE) using a Cai tube. METHODS: From April 2014 to February 2015, we successfully performed total laparoscopic radical surgery with LA-NOSE in six patients with descending colon lesions. The time of operation, blood loss amount, lymph nodes harvested, postoperative recovery, postoperative complications and follow-up were observed. RESULTS: Total laparoscopic dissection and anastomosis with natural orifice removal using a Cai tube was successful in all 6 patients; no deaths, anastomotic bleeding, fistulas, infections, or any other complications were recorded. The median operating time was 327.7 ± 73.4 min, and the estimated blood loss was 66.7 ± 69.2 mL. The mean number of lymph nodes harvested was 15.7 ± 4.4. Recovery of gastrointestinal function ranged from 2 to 4 days after the operation. The mean length of postoperative hospital stay was 12.3 ± 3.2 days. The six cases were followed up for 6-16 (12.5 ± 3.6) months, and all patients avoided auxiliary incision which demonstrated potential cosmetic advantages and uneventful recovery with no additional complications or cancer recurrence. CONCLUSION: In this pilot study of six patients, LA-NOSE radical descending colectomy using a Cai tube was feasible and safe.
