Recovery of Spent Sulphuric Acid by Diffusion Dialysis Using a Spiral Wound Module

In this study, we assess the effects of volumetric flow and feed temperature on the performance of a spiral-wound module for the recovery of free acid using diffusion dialysis. Performance was evaluated using a set of equations based on mass balance under steady-state conditions that describe the free acid yield, rejection factors of metal ions and stream purity, along with chemical analysis of the outlet streams. The results indicated that an increase in the volumetric flow rate of water increased free acid yield from 88% to 93%, but decreased Cu2+ and Fe2+ ion rejection from 95% to 90% and 91% to 86%, respectively. Increasing feed temperature up to 40 °C resulted in an increase in acid flux of 9%, and a reduction in Cu2+ and Fe2+ ion rejection by 2–3%. Following diffusion dialysis, the only evidence of membrane degradation was a slight drop in permselectivity and an increase in diffusion acid and salt permeability. Results obtained from the laboratory tests used in a basic economic study showed that the payback time of the membrane-based regeneration unit is approximately one year.

Cross-Linked Hyaluronic Acid Slows Down Collagen Membrane Resorption in Diabetic Rats through Reducing the Number of Macrophages

Accelerated degradation of collagen membranes (CMs) in diabetic rats is associated with increased infiltration of macrophages and blood vessels. Since pre-implantation immersion of CMs in cross-linked high molecular weight hyaluronic acid (CLHA) delays membrane degradation, we evaluated its effect on the number of macrophages and endothelial cells (ECs) within the CM. Diabetes was induced with streptozotocin in 16 rats, while 16 healthy rats served as control. CM discs were labeled with biotin, soaked in CLHA or PBS and implanted under the scalp. Fourteen days later, CMs were embedded in paraffin and the number of macrophages and ECs within the CMs was determined using antibodies against CD68 and Transglutaminase II, respectively. Diabetes increased the number of macrophages and ECs within the CMs (∼2.5-fold and 4-fold, respectively). Immersion of CMs in CLHA statistically significantly reduced the number of macrophages (p<0.0001) in diabetic rats, but not that of ECs. In the healthy group, CLHA had no significant effect on the number of either cells. Higher residual collagen area and membrane thickness in CLHA-treated CMs in diabetic animals were significantly correlated with reduced number of macrophages but not ECs. Immersion of CM in CLHA inhibits macrophage infiltration and reduces CM degradation in diabetic animals.