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A variety of methods for removing heavy metal ions from wastewater have been developed but because of their low efficiency, further production of toxic sludge or other waste materials, high expense, and lengthy procedures, limited progress has been achieved to date. Polymeric hydrogel has been attracting particular attention for the effective removal of heavy metal ions from wastewater. Here, ionogenic polymeric hydrogels were prepared by free-radical copolymerization of a neutral acrylamide (AAm) monomer with an ionic comonomer in the presence of a suitable initiator and a cross-linker. Different types of ionic comonomers such as strongly acidic: 2-acrylamido-2-methylpropane sulfonic acid, weakly acidic: acrylic acid (AAc), and zwitterionic: 2-methacryloyloxy ethyl dimethyl-3-sulfopropyl ammonium hydroxide with varying amounts were incorporated into the poly(AAm) networks to fabricate the hydrogels. The heavy metal ions (Fe3+, Cr3+, and Hg2+) removal capacity of the fabricated hydrogels from an aqueous solution via electrostatic interactions, coordination bond formation, and a diffusion process was compared and contrasted. The poly(AAm) hydrogel containing weakly acidic AAc groups shows excellent removal capacity of heavy metal ions. The release and recovery of heavy metal ions from the hydrogel samples are also impressive. The compressive strength of hydrogels was found to be significantly high after incorporating heavy metal ions that will increase their potential applications in different sectors.
RESUMO
BACKGROUND: Penetrating nonmissile injuries to the head are far less common than missile penetrating injuries. Here we describe our experience in managing 17 cases of nonmissile injury to the head, likely the largest such series reported to date. We also highlight the surgical steps and techniques used to remove in situ objects (including weapons) in the penetrating wounds that have not been described previously. METHODS: We conducted a retrospective study of cases of nonmissile, low-velocity penetrating injuries of the head managed in our department. The recorded data of patients with penetrating head injuries were studied for the cause of the injury, type of object, type and extent of penetration, Glasgow Coma Scale score on admission, other clinical issues, evaluation and assessment, interval from penetration to operation, surgical steps and notes, difficulty during the operation, major and minor complications, follow-up, and ultimate outcome. RESULTS: Our 17 cases included 6 cases of accidental penetration and 11 cases of penetration as the result of violence. Weapons and other foreign objects causing injury included a teta (a pointed metal weapon with a wooden handle and a barb near the tip, used for hunting and fishing) in 4 cases, a dao (a sharp metal cutting instrument with a wooden handle used for cutting vegetables, fish, meat, bamboo, wood, etc.) in 3 cases, a bamboo stick in 3 cases, a metal rod in 2 cases, a knife in 2 cases, a sharp stone in 1 case, a metal steam chamber cover in 1 case, and a long peg in 1 case. GCS on admission was between 13 and 15 in 15 cases. Only 1 patient exhibited limb weakness. Four patients with an orbitocranial penetrating injury had 1-sided vision loss; 2 of these patients had orbital evisceration, and 1 of these patients died. In 14 patients, the foreign object was in situ at presentation and was removed surgically. Computed tomography scan and plain X-ray of the head were obtained in all patients. Postoperatively, 2 patients (11.7%) needed support in the intensive care unit but died early after surgery. One patient developed late osteomyelitis. The remaining patients were doing well at the most recent follow-up. CONCLUSIONS: The presenting picture of nonmissile penetrating injury to head may be daunting, but these cases can be managed with very good results with proper (clinical and radiologic) evaluation and simple neurosurgical techniques.
