RESUMO
Acid modification has been widely used to modify the structural properties of biochars. However, acid modification led to the large consumption of acid, increased difficulty of waste effluent disposal, and a high application cost. To evaluate the advantages and application potential of biochars prepared under CO2, utilizing pyrolysis to directly modify biochars to improve heavy metal removal efficiency and reduce production cost, would be an important prerequisite for the broad application of biochars. The sorption performance of Pb2+ with CO2-modified biochars was compared with that of HNO3-modified biochar. The elemental compositions and structural properties of biochars were characterized through elemental analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results revealed that for biochars produced at 500â, HNO3 modification produced abundant carboxylic groups and -NO2 (asy) and -NO2 (sym) groups, promoting the surface activities and complexing abilities of biochars. The CO2-modified biochars contained abundant carbonate minerals, which could remove Pb2+ by electrostatic ion exchange and coprecipitation or complex. In addition, compared to that of HNO3-modified biochars, CO2-modified biochars had the larger specific surface area and better microporous structures, which were beneficial to the diffusion of Pb2+ and further promoted surface sorption. CO2 modification increased the maximum Pb2+ sorption capacity of W500CO2 and W700CO2, which were 60.14 mg·g-1 and 71.69 mg·g-1. By contrast, HNO3-modified biochars W500N2-A and W700N2-A showed the lower Pb2+ sorption capacities, which were 42.26 mg·g-1 and 68.3 mg·g-1, respectively. The increasing of the specific surface area and functional groups simultaneously promoted the sorption capacity of CO2-modified biochars. Consequently, the CO2-modified biochar had the advantages of low cost, environmental friendliness, and high heavy metal removal efficiency, which is a modification method worthy of promotion and application.
RESUMO
OBJECTIVE: To compare clinical efficacy of repositioning with precise-surgical-opening intramedullary nail insertion and traditional repositioning in treating unstable femoral intertrochanteric fractures with closed-reposition difficulty. METHODS: Clinical data of 58 patients with unstable femoral intertrochanteric fractures after closed-reposition difficulty (AO 31A2.2-3.3) were retrospective analyzed. Among them, 32 patients were treated with first open intramedullary nail and then reduction operation(modified reductuon group) including 9 males and 23 females with an average age of (80.9±11.1) years old ranging from 46 to 99 years old; and 26 patients were treated by traditional reduction(traditional reduction group) including 7 males and 19 females with an average of(78.1±13.9) years old ranging from 41 to 89 years old. The time of operation, the amount of bleeding, the length of hospital stay, the first weight-bearing time and the time of fracture healing, postoperative complications and Harris hip score were evaluated and compared between the two groups. RESULTS: All patients were followed up for 12 to 24 months with an average of 17.3 months. The operative time(t=3.612, P=0.008 2) nd the blood loss(t=3.389, P=0.007 5) in the modified reduction group were lower than those in the traditional reduction group. There were no significant differences in hospitalization time(t=0.851, P=0.392), fracture healing time(t=0.640, P=0.531), and the first loading time(t=0.845, P=0.411) between two groups. There was no significant difference in the Harris score between two groups(χ²=0.66, P=0.831>0.05). CONCLUSIONS: Traditional repositioning requires a repositioning of the fracture bone and a correct opening reaming before the insertion and fixture of the intramedullary nail, which is a complicated operation in unstable femoral intertrochanteric fractures after closed-reposition difficulty. On the other hand, the new method implements the insertion of the intramedullary nail before the repositioning of the fracture bone, greatly simplifying the operation procedure, shortening the total operation time and reducing the amount of intraoperative blood loss.
