MnO4(-) was activated by HSO3(-), resulting in a process that oxidizes organic contaminants at extraordinarily high rates. The permanganate/bisulfite (PM/BS) process oxidized phenol, ciprofloxacin, and methyl blue at pHini 5.0 with rates (kobs ≈ 60-150 s(-1)) that were 5-6 orders of magnitude faster than those measured for permanganate alone, and ∼5 to 7 orders of magnitude faster than conventional advanced oxidation processes for water treatment. Oxidation of phenol was fastest at pH 4.0, but still effective at pH 7.0, and only slightly slower when performed in tap water. A smaller, but still considerable (∼3 orders of magnitude) increase in oxidation rates of methyl blue was observed with MnO2 activated by HSO3(-) (MO/BS). The above results, time-resolved spectroscopy of manganese species under various conditions, stoichiometric analysis of pH changes, and the effect of pyrophosphate on UV absorbance spectra suggest that the reactive intermediate(s) responsible for the extremely rapid oxidation of organic contaminants in the PM/BS process involve manganese(III) species with minimal stabilization by complexation. The PM/BS process may lead to a new category of advanced oxidation technologies based on contaminant oxidation by reactive manganese(III) species, rather than hydroxyl and sulfate radicals.

Activation of Manganese Oxidants with Bisulfite for Enhanced Oxidation of Organic Contaminants: The Involvement of Mn(III)

Increasing demands for environmental accountability and energy efficiency in industrial practice necessitates significant modification(s) of existing technologies and development of new ones to meet the stringent sustainability demands of the future. Generally, development of required new technologies and appropriate modifications of existing ones need to be premised on in-depth appreciation of existing technologies, their limitations, and desired ideal products or processes. In the light of these, published literature mostly in the past 30 years on the sealing process; the second highest energy consuming step in aluminum anodization and a step with significant environmental impacts has been critical reviewed in this systematic review. Emphasis have been placed on the need to reduce both the energy input in the anodization process and environmental implications. The implications of the nano-porous structure of the anodic oxide on mass transport and chemical reactivity of relevant species during the sealing process is highlighted with a focus on exploiting these peculiarities, in improving the quality of sealed products. In addition, perspective is provided on plausible approaches and important factors to be considered in developing sealing procedures that can minimize the energy input and environmental impact of the sealing step, and ensure a more sustainable aluminum anodization process/industry.

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The Sealing Step in Aluminum Anodizing: A Focus on Sustainable Strategies for Enhancing Both Energy Efficiency and Corrosion Resistance

Applying advanced oxidation processes (AOPs) in sludge dewatering to improve sludge treatment, disposal and environmental protection has attracted much interest due to the difficulties arising in extracellular polymeric substances (EPS) degradation during the sludge dewatering process. Oxidants can produce different types of free radicals and exert specific oxidation effects through different action mechanisms on water saturated sludge. This plays an important role in sludge dewatering, sludge minimization and removal of different types of micropollutants and/or their transformation. The current review critically evaluates the role of AOP in improving the efficiency of sludge dewatering. Characteristics of advanced oxidation methods applied to sludge dewatering are systematically illustrated through different mechanisms using free radical reactions and various sludge dewatering conditions. Factors which impact on influencing the minimization of sludge and removals of typical micropollutants during the sludge conditioning process are also analyzed. Finally, applications of advanced oxidation methods in the future are proposed based on a technoeconomic analyses of dewatering efficiency and operation cost. This review provides theoretical support regarding the application of advanced oxidation processes in sludge dewatering and avenues for practical engineering. In the current review, it is determined that the efficiency of AOP for the improvement of sludge dewatering, micropollutants removal and sludge minimization in the treatment and disposal of sludge have been fully investigated. Unfortunately, there is still lack of comparing the ability of different free radicals on published review. 

Advanced oxidation processes (AOPs)-based sludge conditioning for enhanced sludge dewatering and micropollutants removal: A critical review

Emerging organic contaminants and odorous compounds in secondary effluent wastewater: Identification and advanced treatment.

Synchronous sequestration of cadmium and fulvic acid by secondary minerals from Fe(II)-catalyzed ferrihydrite transformation

Microbial metabolism changes molecular compositions of riverine dissolved organic matter as regulated by temperature.

Metabolites of algae such as geosmin, 2-methylisoborneol etc. are reported to induce pungent odors into drinking water and attract additional scientific attention. Recently, in China, taste and odor outbreaks in drinking water supply have become increasingly common. In source water affected by eutrophication, dimethyl trisulfide, speculated to be produced by decayed algae, was found to be the source of taste and odor issues and can be removed effectively by usual oxidation agents. In this experimental study, batch scale tests were carried out focusing on the removal of dimethyl trisulfide. Reaction kinetics of dimethyl trisulfide oxidized by potassium permanganate in water had been studied; influence factors such as pH, organic substrate, other existed taste, and odor contaminant in equivalent concentration were also discussed. Results showed that dimethyl trisulfide can be removed by potassium permanganate efficiently; the ratio can reach more than 70% with oxidant dosage of 4 mg·L−1 and contact time prolonged to 120 min. The dimethyl trisulfide decomposition followed a second-order kinetics pattern with a rate constant k = 0.00213 L·(min·mg)−1. Typically, the degradation rate of dimethyl trisulfide was increased with the increasing KMnO4 dosage, but dramatically dropped with the increasing levels of humic acid (1.8–4.5 mg·L−1) and other odor-causing compounds (e.g. β-cyclocitral, 0−1886.0 μg·L−1). Solution pH (5.2–9.0) and initial dimethyl trisulfide concentration did not significantly affected the degradation. This study demonstrates that KMnO4 oxidation is an effective option to remove dimethyl trisulfide from water.

Kinetics of oxidation of dimethyl trisulfide by potassium permanganate in drinking water

Iron (Fe) oxides and fulvic acid (FA) are the key components affecting the fate of cadmium (Cd) in soil. The presence of FA influences Fe mineral transformation, and FA may complicate phase transformation and dynamic behavior of Cd. How varying Fe minerals and FA affect Cd immobilization during the ferrihydrite transformation induced by various Fe(II) concentrations, however, is still lack of quantitative understanding. In this study, we built a model for Cd species quantification during phase transformation based on mechanistic insights obtained from batch experiments. Spectroscopic analysis showed that Fe(II) concentrations affected secondary Fe minerals formation under the condition of co-existence of Cd and FA, and ultimately changed the distribution of Cd and FA. Microscopic analysis revealed that besides surface adsorption, part of Cd was sequestrated by magnetite, whereas FA was able to diffuse into lepidocrocite defects. The model revealed that adsorbed Cd was mainly controlled by FA and ferrihydrite, and direct complexation of Cd by FA had a strong impact on the continuous change in Cd at lower Fe(II) concentration. The results contribute to an in-depth understanding of the mobility of Cd in the environment and provide a method for quantifying the dynamic behavior of heavy metals in multi-reactant systems.

Mechanistic and modeling insights into the immobilization of Cd and organic carbon during abiotic transformation of ferrihydrite induced by Fe(II).

The removal of algae and odorous metabolite dimethyl trisulfide (DMTS) in water using potassium ferrate (K2FeO4) was investigated. The treatment effect was compared with polyferric chloride (PFC) and potassium permanganate (KMnO4) pre-oxidation followed by PFC. Factors such as pH, oxidation contact time, and turbidity were also analyzed. The results show that K2FeO4 is more effective in algae elimination than PFC, with a higher removal ratio of 92.4% when dosage is equivalently measured by Fe. Removal of DMTS by K2FeO4 is better than pre-oxidized KMnO4, with decreased oxidation contact time. The removal ratio of DMTS by K2FeO4 was 92.5% with contact time set to 1 min; in comparison, KMnO4 had a removal ratio of only 74.6% after 10 min of contact.

Shi-fei Hu

Papers

Synchronous sequestration of cadmium and fulvic acid by secondary minerals from Fe(II)-catalyzed ferrihydrite transformation

Microbial metabolism changes molecular compositions of riverine dissolved organic matter as regulated by temperature.

Kinetics of oxidation of dimethyl trisulfide by potassium permanganate in drinking water

Mechanistic and modeling insights into the immobilization of Cd and organic carbon during abiotic transformation of ferrihydrite induced by Fe(II).

Simultaneous removal of algae and its odor metabolites in raw water by potassium ferrate