Adsorptive Removal of Nitrate from Aqueous Solution Using Nitrogen Doped Activated Carbon.

Activated carbon (AC) has been widely applied for adsorptive removal of organic contaminants from aqueous phase, but not for ionic pollutants. In this study, nitrogen doped AC was prepared to increase the adsorption capacity of nitrate from water. AC was oxidized with (NH4)2S2O8 solution to maximize oxygen content for the first step, and then NH3 gas treatment was carried out at 950°C to aim at forming quaternary nitrogen (N-Q) species on AC surface (Ox-9.5AG). Influence of solution pH was examined so as to elucidate the relationship between surface charge and adsorption amounts of nitrate. The results showed that Ox-9.5AG exhibited about twice higher adsorption capacity than non-treatment AC at any initial nitrate concentration and any equilibrium solution pH (pHe) investigated. The more decrease in pHe value, the more adsorption amount of negatively charged nitrate ion, because the surface charge of AC and Ox-9.5AG could become more positive in acidic solution. The oxidation and consecutive ammonia treatments lead to increase in nitrogen content from 0.35 to 6.4% and decrease in the pH of the point of zero charge (pHpzc) from 7.1 to 4.0 implying that positively charged N-Q of a Lewis acid was created on the surface of Ox-9.5AG. Based on a Langmuir data analysis, maximum adsorption capacity attained 0.5-0.6 mmol/g of nitrate and adsorption affinity was 3.5-4.0 L/mmol at pHe 2.5 for Ox-9.5AG.

Effect of Polarity of Activated Carbon Surface, Solvent and Adsorbate on Adsorption of Aromatic Compounds from Liquid Phase.

In this study, introduction of acidic functional groups onto a carbon surface and their removal were carried out through two oxidation methods and outgassing to investigate the adsorption mechanism of aromatic compounds which have different polarity (benzene and nitrobenzene). Adsorption experiments for these aromatics in aqueous solution and n-hexane solution were conducted in order to obtain the adsorption isotherms for commercial activated carbon (BAC) as a starting material, its two types of oxidized BAC samples (OXs), and their outgassed samples at 900 °C (OGs). Adsorption and desorption kinetics of nitrobenzene for the BAC, OXs and OGs in aqueous solution were also examined. The results showed that the adsorption of benzene molecules was significantly hindered by abundant acidic functional groups in aqueous solution, whereas the adsorbed amount of nitrobenzene on OXs gradually increased as the solution concentration increased, indicating that nitrobenzene can adsorb favourably on a hydrophilic surface due to its high dipole moment, in contrast to benzene. In n-hexane solution, it was difficult for benzene to adsorb on any sample owing to the high affinity between benzene and n-hexane solvent. On the other hand, adsorbed amounts of nitrobenzene on OXs were larger than those of OGs in n-hexane solution, implying that nitrobenzene can adsorb two adsorption sites, graphene layers and surface acidic functional groups. The observed adsorption and desorption rate constants of nitrobenzene on the OXs were lower than those on the BAC due to disturbance of diffusion by the acidic functional groups.

Effects of tunnel dilation and interference screw position on the biomechanical properties of tendon graft fixation for anterior cruciate ligament reconstruction.

PURPOSE: The purpose of this study was to evaluate the effects of screw position and compaction of the bone tunnel on the strength of the flexor tendon graft after fixation using interference screws. METHODS: Forty fresh-frozen porcine tibias were used for this study. The digital flexor tendons were folded into a quadrupled graft measuring 9 mm in diameter. In the extraction-drilling group, tibial bone tunnels were drilled with a conventional cannulated 9-mm drill bit in a single step. In the compaction-drilling group, bone tunnels were drilled using a cannulated 7-mm drill bit and were expanded to a final diameter of 9 mm in 0.5-mm increments by placement of dilators with increasing diameter. The grafts were fixed using 9 × 30-mm titanium screws in central and eccentric positions. Specimens underwent a cyclic-loading test, and the surviving specimens were then loaded until failure. RESULTS: Graft displacement after 1,500 loading cycles occurred significantly more often in the extraction-drilling group with eccentric screw placement than in the groups of extraction-drilling (P < .05) and compaction-drilling (P < .01) with central screw placement. There were no statistically significant differences for the maximum screw insertion torque, maximum load at failure, or stiffness among the 4 groups. One strand of the quadrupled tendon grafts showed partial injury during screw insertion in 3 (30%) and 4 (40%) of 10 specimens of the extraction-drilling and compaction-drilling groups with central screw placement, respectively. CONCLUSIONS: Central screw placement significantly decreased the displacement of the tendon graft in comparison with eccentric screw placement in the extraction-drilling condition. Compaction of the bone tunnel walls by serial dilation in a central screw position did not increase the strength of interference screw fixation of a soft tissue graft. CLINICAL RELEVANCE: When using the extraction method and fixing the graft in an eccentric position, it is advisable to provide additional fixation outside the tunnel to prevent slippage of the graft.

Repair integrity evaluated by second-look arthroscopy after arthroscopic meniscal repair with the FasT-Fix during anterior cruciate ligament reconstruction.

BACKGROUND: Although several devices for meniscal repairs have become available, a successful outcome is ultimately due to a healed meniscus on the clinical findings. The authors assessed the repair integrity after meniscal repair with the FasT-Fix device using second-look arthroscopy. HYPOTHESIS: Meniscal repair with the FasT-Fix will lead to arthroscopically evident healing, but some menisci will show incomplete healing even in clinically successful cases and have newly formed injuries on the meniscal substance resulting from the path of the implant. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Sixty-five consecutive patients were studied, in whom 84 menisci were subjected to all-inside meniscal repair with the FasT-Fix device in conjunction with anterior cruciate ligament reconstruction. Repair was only performed on longitudinal or double longitudinal tears within the red-red or red-white zone. The repaired menisci were evaluated by second-look arthroscopy at the time of staged hardware removal after anterior cruciate ligament reconstruction. RESULTS: Sixty-two meniscal tears in 46 patients were available for this study. Eight patients were found to be symptomatic and considered to be clinical failures. The clinical success rate was 83%. At second-look arthroscopy, 46 tears (74%) were healed, 9 (15%) were healed incompletely, and 7 (11%) had failed. In the failed menisci, 1 had meniscal symptoms, while the other 6 were asymptomatic. In the 9 menisci with incomplete healing, 3 were associated with nonspecific knee pain but none showed meniscal symptoms. Newly formed injuries, which occurred in an area different from the original repair site, were confirmed on the surface of 19 menisci (35%) among the healed and incompletely healed menisci. Thirty menisci (48%) displayed successful and complete healing of the original tear site without newly formed tears. CONCLUSION: Meniscal repair with the FasT-Fix in conjunction with anterior cruciate ligament reconstruction resulted in complete healing in 74% of cases. Eighty-three percent of menisci were symptom-free regardless of meniscal integrity. Even when the menisci repaired are asymptomatic and considered to be a clinical success, however, there may be newly formed injuries.

Intra-articular ganglia arising from the posterior joint capsule of the knee.

Magnetic resonance imaging (MRI) is an effective method to evaluate cystic lesions of the knee. Intra-articular ganglia of the knee joint was considered to be rare before the advent of MRI. However, because an MRI is often used to diagnose knee pathology, the reported prevalence of intra-articular ganglia has increased. We describe two cases of an intra-articular ganglion arising from the posterior joint capsule. Both cysts appeared to be arising from the posterior cruciate ligament by both MRI as well as arthroscopy through a lateral infrapatellar portal. However, arthroscopy through a posteromedial portal revealed the cysts to originate from the posterior joint capsule. It suggests that some of the ganglion arising from the posterior cruciate ligament reported in the literature might actually be from the posterior joint capsule. To prevent recurrence of a ganglion cyst, when preoperative MRI shows the mass to be located posterior to the cruciate ligaments, we recommend that the relationship of the ganglion cyst to the posterior joint capsule be evaluated at arthroscopy through the posteromedial or posterolateral portal.