Mechanistic Study of Arsenate Adsorption onto Different Amorphous Grades of Titanium (Hydr)Oxides Impregnated into a Point-of-Use Activated Carbon Block.

Millions of households still rely on drinking water from private wells or municipal systems with arsenic levels approaching or exceeding regulatory limits. Arsenic is a potent carcinogen, and there is no safe level of it in drinking water. Point-of-use (POU) treatment systems are a promising option to mitigate arsenic exposure. However, the most commonly used POU technology, an activated carbon block filter, is ineffective at removing arsenic. Our study aimed to explore the potential of impregnating carbon blocks with amorphous titanium (hydr)oxide (THO) to improve arsenic removal without introducing titanium (Ti) into the treated water. Four synthesis methods achieved 8-16 wt.% Ti loading within the carbon block with 58-97% amorphous THO content. The THO-modified carbon block could adsorb both oxidation states of arsenic (arsenate and arsenite) in batch or column tests. Modified carbon block with higher Ti and amorphous content always led to better arsenate removal, achieving arsenic loadings up to 31 mg As/mg Ti after 70,000 bed volumes in continuous flow tests. Impregnating carbon block with amorphous THO consistently outperformed impregnation using crystalline TiO2. The best-performing system (TTIP-EtOH carbon block) was an amorphous THO derived using titanium isopropoxide, ethanol, and acetic acid via sol-gel technique, aged at 80° for 18 hours and dried overnight at 60°. Comparable pore size distribution and surface area of the impregnated carbon blocks suggested that chemical properties play a more crucial role than physical and textural properties in removing arsenate via amorphous Ti-impregnated carbon block. Freundlich isotherms indicated energetically favorable adsorption for amorphous chemically synthesized adsorbents. The mass transport coefficients for the amorphous TTIP-EtOH carbon block were fitted using a pore surface diffusion model, resulting in Dsurface = 3.1×10-12 cm2/s and Dpore = 3.2×10-6 cm2/s. Impregnating the carbon block with THO enabled effective arsenic removal from water without adversely affecting the pressure drop across the unit or the carbon block's ability to remove polar organic chemical pollutants efficiently.

Adult intussusception due to lymphangioma of the colon.

We present herein a case report of adult intussusception due to lymphangioma of the colon. On May 27, 2000, a 39-year-old woman with right lower abdominal pain was admitted to our hospital. Preoperative imaging studies, by ultrasonography, computed tomography (CT), and barium enema examination, showed right colon intussusception with a multilocular cystic tumor as a leading point. Emergency operation was performed. During the operation, normograde ileocecal intussusception with a 9 x 6-cm soft submucosal tumor of the cecum was recognized. Ileocecal resection was performed, and the patient's postoperative course was uneventful. Pathological diagnosis of the resected specimen was a cystic type lymphangioma of the cecum. Recently, lymphangioma of the colon has been diagnosed more frequently by colonoscopy and endoscopic ultrasonography. However, only a few cases of colon intussusception due to lymphangioma have been reported in the literature to date. Large lymphangioma of the colon is rare, but it should be taken into consideration that it is one of the organic lesions that causes adult intussusception.