Effective degradation of Direct Red 81 using FeS-activated persulfate process.

As a burgeoning advanced oxidation process (AOP), heterogeneous activation of persulfate (PS) for synthetic refractory contaminants decontamination has recently received much attention. In this study, FeS was selected as a heterogeneous PS activator to facilitate the degradation of a typical recalcitrant contaminant of diazo dye Direct Red 81 (DR 81). The results showed that approximately 95% of 0.03 mM DR 81 was removed within 60 min with FeS and PS doses of 1.5 × 10-3 M. The efficient decomposition of DR 81 by the FeS/PS system was assumed to be mainly attributed to the highly reactive SO4-• and •OH, which was related to PS cleavage by both dissolved Fe2+ leached from FeS and Fe2+ bound on the FeS surface. Except for strongly alkaline conditions, DR 81 decolorations by FeS/PS were insignificantly affected by operational parameters such as temperature, initial solution pH, and rotate speed. Meanwhile, the presence of five inorganic anions being studied had distinct impacts on DR 81 degradation and followed a strict order of NO3- < Cl- < SO42- < CO32- < PO43-. However, FeS/PS system was highly adaptable, and FeS, which is used as a PS activator was more stable. GC/MS and TOC data revealed that thorough mineralization of DR 81 by PS/FeS in an initial fast reaction phase to transform DR 81 to aromatic intermediates, followed by a slow reaction phase that mineralized these organic intermediates into carboxylic acids and carbon dioxide through further oxidation.

Decolorization of azo dyes in a heterogeneous persulfate system using FeS as the activator.

Textile effluents containing synthetic refractory azo dyes are one of the most important sources of water pollution. However, these kinds of refractory organic pollutants did not resist a persulfate (PS) oxidation process which was correctly activated. In this study, PS was activated by ferrous sulfide (FeS) in a heterogeneous system to break down azo dyes wastewater. The results showed that all five selected azo dyes were efficiently broken down using the PS/FeS system, except for DY 12, and more than 95% of azo dyes were decolored within 60 minutes. The decolorization efficiency of DR 81 in the PS/FeS system was comparable to PS activated with heat (60 °C) or Fe2+, and was slightly superior to Fe0 powders under the same conditions. Quenching studies indicated that both SO4-• and •OH were formed in the FeS surface and diffused into the solution to facilitate the successive transformation of DR 81, the •OH reaction with DR 81 might the crucial reaction. The coexisting chelating agents in real azo dye effluents at high concentrations had a negative influence on azo dye decolorization by PS/FeS. However, the superior factor of the PS/FeS system was the regenerability and reusability of the heterogeneous catalyst.

Characterization of Magnetic Biochar Modified Using the One-Step and Electrochemical Methods and Its Impact on Phosphate Adsorption.

The properties and phosphate adsorption capability of the one-step method and electrochemical method in modifying peanut shell biochar have been determined. The one-step method deposits MgO and Fe3O4 onto biochar through chemical impregnation and regularly affects the functional groups and magnetic separation of biochar, thereby enhancing its ability to adsorb phosphate. In contrast, the electrochemical method is not favorable for modifying functional groups of biochar but can promote phosphate adsorption because of the formation of MgFe2O4 and Fe3O4 using electrolysis. The adsorption isotherm and kinetics data suggest that adsorption is monolayer onto a homogeneous surface and phosphate adsorption could be controlled by chemical processes. Biochar with the addition of both Fe2+ and Mg2+ shows better phosphate adsorption capability than those with barely any Fe2+ additions. It was concluded that the one-step method is a better modification method than the electrochemical method for enhancing the phosphate adsorption capability of biochars.

The application of surfactant colloidal gas aphrons to remediate contaminated soil: A review.

Surfactant solutions have been frequently studied for soil remediation. However, since they are expensive, massive consumption of surfactant solution can constrain their application. Surfactant microbubbles, or colloidal gas aphrons (CGAs), can serve as cost effective alternatives of surfactant solution because the use of CGAs reduce the amount of surfactant consumption. Moreover, CGAs can also improve the contact with the contaminated environment due to their unique surface properties, e.g. containing 40-70% of gas, small size, large interfacial areas, water-like flow properties and buoyant rise velocities. In this review paper, the properties and flow character of CGAs in soil matrix reviewed due to their relevance to soil remediation process. A comprehensive overview of the application of CGAs in flushing off organic pollutants and heavy metals, and carrying oxygen, bacteria and dissolved materials for soil remediation were provided. This paper also highlighted the limitation of CGAs application and important future research scopes.

Cellulose/vaterite nanocomposites: Sonochemical synthesis, characterization, and their application in protein adsorption.

Vaterite is recognized as an important biomedical material owing to its features such as high specific surface area, high solubility, high dispersion, and small specific gravity. Herein, we report a facile and green sonochemical route to prepare vaterite nanospheres (assembled from rice-shaped nanoparticles) with average diameter of 206-246 nm by using cellulose as substrate. The important role of cellulose concentration on the phase of the products was systematically investigated, and the formation mechanism of vaterite was proposed. Moreover, the as-prepared cellulose/vaterite nanocomposites have a good cytocompatibility and a relatively high protein adsorption ability using hemoglobin as a model protein. These results indicate that the as-prepared cellulose/vaterite nanocomposites are promising for applications in biomedical fields, such as protein adsorption.

Performance of green waste biocovers for enhancing methane oxidation.

Green waste aged 2 and 24months, labeled "fresh" and "aged" green waste, respectively, were placed in biocover test cells and evaluated for their ability to oxidize methane (CH4) under high landfill gas loading over a 15-month testing period. These materials are less costly to produce than green waste compost, yet satisfied recommended respiration requirements for landfill compost covers. In field tests employing a novel gas tracer to correct for leakage, both green wastes oxidized CH4 at high rates during the first few months of operation - 140 and 200g/m(2)/day for aged and fresh green waste, respectively. Biocover performance degraded during the winter and spring, with significant CH4 generated from anaerobic regions in the 60-80cm thick biocovers. Concurrently, CH4 oxidation rates decreased. Two previously developed empirical models for moisture and temperature dependency of CH4 oxidation in soils were used to test their applicability to green waste. Models accounted for 68% and 79% of the observed seasonal variations in CH4 oxidation rates for aged green waste. Neither model could describe similar seasonal changes for the less stable fresh green waste. This is the first field application and evaluation of these empirical models using media with high organic matter. Given the difficulty of preventing undesired CH4 generation, green waste may not be a viable biocover material for many climates and landfill conditions.