Preparation of Mn/Mg/Ce Ternary Ozone Catalyst and Its Mechanism for the Degradation of Printing and Dyeing Wastewater

The printing and dyeing wastewater produced by different dyes, as well as different printing and dyeing processes, have different components. These wastewater have high toxicity, high organic concentration, and deep chromaticity. Ozone catalytic oxidation is a very promising technical method for wastewater treatment. In this paper, Mn/Mg/Ce ternary catalyst was prepared, and the ozone catalytic oxidation treatment of actual and simulated printing and dyeing wastewater was performed to study the performance of four different carrier catalysts, namely, molecular sieve (MS), silica gel (SG), attapulgite (ATP), and nano alumina (Al2O3), by simulated dynamic test. The effects of reaction time, pH, and catalyst dosage on methyl orange degradation were studied. The results showed that under the optimum treatment conditions (120 min, pH 11, and 12.5 g/L catalyst dosage), the degradation rate of methyl orange reached 96% and the removal rate of the chemical oxygen demand of printing and dyeing wastewater reached 48.7%. This study shows that the treatment effect of ozone catalytic oxidation on printing and dyeing wastewater is remarkably improved after catalyst addition. This study provides a new choice of ozone catalyst for the degradation of printing and dyeing wastewaters in the future.

Biotribological performance of medical-grade UHMW polyethylene-based hybrid composite for joint replacement

Ultra high molecular weight polyethylene (UHMWPE) is widely used for articulating surfaces in total hip and knee replacements. In the present work, the tribological properties of UHMWPE-based nano composites were studied in order to meet the demands of current bearing applications. UHMWPE matrix reinforced with 0.5, 1, and 2 weight percentage of alumina nano powder were fabricated by hot pressing. The dispersion and microstructure of composite material was established by X-ray diffraction (XRD) and scanning electron microscope (SEM) micrograph. The tests were carried out on a reciprocating sliding pin-on-disc tribometer at human body temperature (37±1°C) under dry and human serum lubricating environments for a normal load of 46 N and 52 N, a constant sliding speed of 4 mm. Under these testing conditions, it has been observed that the wear behavior of the developed composites improved with increase in weight percentage of alumina nano powder. The results show that at 52 N load, the maximum value of wear rate was 7.9x10−7 mm3/Nm and the minimum value 1.6x10−7 mm3/Nm was obtained. SEM was used to examine the worn surface and it was observed that human serum adheres to the surface of the composite pins upon sliding, resulting in the formation of a film which results in better wear resistance of the composite pins under human serum lubrication than dry sliding. This study implies that the use of nano alumina power will reduce the wear of UHMWPE based composite under human serum lubrication.

Effect of Nano-Additives on the Strength and Durability Characteristics of Marl

Low bearing capacity soils may pose serious construction concerns such as reduced bearing capacity and excessive hydro-associated volume changes. Proper soil remediation techniques must be planned and implemented before commencing any construction on low bearing capacity soils. Environmentally friendly soil stabilizers are gradually replacing traditional soil stabilizers with high carbon dioxide emissions such as lime and cement. This study investigated the use of an alternative pozzolanic mix of nano-additives (i.e., nano-silica and nano-alumina) and cement to reduce the usage of cement for achieving competent soil stabilization outcomes. A series of unconfined compressive strength (UCS), direct shear, and durability tests were conducted on marl specimens cured for 1, 7, and 28 days stabilized with nano-additives (0.1~1.5%), 3% cement, and combined 3% cement and nano-additives. The UCS and shear strength of stabilized marl increased with nano-additives up to a threshold nano-additive content of 1% which was further intensified with curing time. Nano-additive treated cemented marl specimens showed long durability under the water, while the cemented marl decomposed early. The microfabric inspection of stabilized marl specimens showed significant growth of calcium silicate hydrate (CSH) products within the micro fabric of nano-silica treated marl with reduced pore-spaces within aggregated particles. The results confirmed that nano-additives can replace cement partially to achieve multi-fold improvement in the strength characteristics of the marl.