Synthesis of Atmospherically Stable Zero-Valent Iron Nanoparticles (nZVI) for the Efficient Catalytic Treatment of High-Strength Domestic Wastewater

Here, we report the fabrication of nZVI by the wet chemical technique in the presence of ethanol using ferric iron and sodium borohydride as the reducing agents under ambient conditions. The obtained nZVI particles are mainly in a zero-valent oxidation state and do not undergo significant oxidation for several weeks. The structural and morphological parameters of nZVI were investigated by using UV, XRD, SEM, EDX, TEM, and DLS analysis. The optical nature, bandgap energy, and absorption edge were all revealed by the UV–visible spectrum. The phase development and crystallinity of nZVI particles were shown by the XRD pattern. The morphological investigation revealed that the nanoparticles were spherical with an average size of 34–110 nm by using ImageJ software, and the elemental analysis was analyzed using EDX. Furthermore, the catalytic treatment performance of domestic wastewater was evaluated in terms of pH, COD (chemical oxygen demand) solubilization, total solids (TS), volatile solids (VS), phosphorous, and total nitrogen (TN) reduction under aerobic and anaerobic operating conditions. The effluent was subjected to a process evaluation with a different range (100–500 mg/L) of nZVI dosages. The COD solubilization and suspended solids reduction were significantly improved in the anaerobic condition in comparison to the aerobic condition. Furthermore, the effect of nZVI on phosphorous (PO43−) reduction was enhanced by the electrons of iron ions. The high concentration of nZVI dosing has a positive impact on COD solubilization and phosphorous removal regardless of the aeration condition with 400 mg/L of nZVI dosage.

Kinetics of catalytic treatment of coking wastewater (COD, phenol and cyanide) using wet air oxidation

Coking wastewater (CWW) is known as a highly polluting effluent. This study deals with the degradation of pollutants in terms of COD, phenol and cyanide present in CWW using catalytic wet air oxidation (CWAO) process. CWAO was carried out in batch mode using various catalysts. The investigated operating parameters are initial pH (pH i ) 3–11, temperature (T) 100–160 °C, air partial pressure (p air) 2–6 MPa, catalyst mass loading (C w ) 2–5 g/L and treatment time (t R ) of 0–6 h. Among various catalysts, the copper chloride was proved to be best for degradation of pollutants. The optimum conditions were evaluated for the degradation of organic compounds as T 130 °C, p air 8.8 MPa, C w 3 g/L and t R = 6 h. The maximum percentage reduction of COD, phenol, and cyanide was achieved through experiment at T 160 °C, p air 12.2 MPa, C w 5 g/L and t R 6 h as 97.32%, 97.94% and 99.87%, respectively. The kinetics studies were also performed to evaluate the rate constant (k), and reaction order with respect to COD, phenol, CN, CW and p air.

Recent Advances in the Catalytic Treatment of Volatile Organic Compounds: A Review Based on the Mixture Effect

Catalytic total oxidation is an efficient technique for treating VOCs, which are mainly emitted by solvent-based industrial processes. However, studies of the catalytic oxidation of VOCs in combination with other pollutants are very limited, despite the fact that this is a key step of knowledge before industrial application. During the oxidation reaction, the behavior of a molecule may change depending on the reaction mixture. For the treatment of an effluent loaded with VOCs, it is necessary to carefully select not only the catalytic material to be used but also the reaction conditions. Indeed, the catalytic oxidation of a component in a VOCs mixture is not predicted solely from the behavior of individual component. Thus, the objective of this small review is to carry out a study on the effect observed in the case of the oxidation of a VOCs mixture or in the presence of water, NOX or sulfur compounds.

Application of Pd-Sn Modified Ru-Ir Electrode For Treating High Chlorine Ammonia-Nitrogen Wastewater

Electro-catalytic technology has attracted increasing attention as a promising approach for wastewater treatment, owing to its easy operation, minimal generation of secondary pollution, small foot-print and rapid start-up. In this work, the chlorine evolution potential of the Pd-Sn modified ruthenium(Ru)-iridium(Ir) electrode was investigated for electro-catalytic treatment of high chlorine ammonia-nitrogen wastewater. The effect of reaction conditions on the removal of ammonia-nitrogen, kinetics and apparent activation energy of the electro-catalytic treatment of ammonia-nitrogen were studied. The possible denitrification process of high chlorine ammonia-nitrogen wastewater treated by electrocatalysis was discussed. The results indicated that the chlorine evolution potential of the Pd-Sn modified Ru-Ir electrode was 1.0956 V(vs. SCE). The rule of electro-catalytic treatment of high chlorine ammonia-nitrogen conformed to zero-order kinetics, and the removal process was endothermic reaction with the apparent activation energy of 14.089 kJ/mol. With the current is 0.5 A, the removal efficiency of ammonia-nitrogen could achieve 100% at the reaction time of 40 min. Indirect oxidation played an essential role in the electro-catalytic ammonia-nitrogen removal using the Pd-Sn modified Ru-Ir electrode. This paper demonstrated that the electro-catalytic technology was a promising approach for efficiently treating the high chlorine ammonia-nitrogen wastewater.

CATALYTIC TREATMENT OF SALINE EFFLUENTS

Процессы окисления органических и неорганических веществ занимают важное место в современной химии и технологии. Представляется естественным, что подобные процессы должны быть полифункциональными и высокоэффективными. Кроме того, весьма желательно, чтобы они происходили в достаточно мягких условиях – идеальными условиями (пока в большинстве случаев труднодостижимыми) являются атмосферное давление и комнатная температура. В настоящее время большинство процессов, используемых в промышленности, идут с достаточно высокой селективностью, и требуют для своего осуществления соответственно жестких условий (температура выше 100°С и повышенное давление). Более селективными и менее энергоемкими во многих случаях оказываются процессы, использующие в качестве окислителей связанный кислород (перманганаты, бихроматы, гипохлориты, различные пероксиды). Однако такие окислители находят применение только для малотоннажных продуктов, поскольку, как правило, достаточно дороги и дефицитны. Кроме того, их использование часто приводит к образованию не утилизируемых отходов. Поэтому реально в качестве окислителя для обезвреживания НДМГ, ДМА, метанола мы можем рассматривать только молекулярный кислород. Этот окислитель дешев, а единственными отходами процесса являются продукты окисления это вода, азот и СО2. Поэтому, поиск новых каталитических систем в этой области представляет собой важную и интересную задачу. Перспективным классом соединений, среди которых уже найдены подобные катализаторы, являются соединения переходных металлов, в частности, кобальта, никеля, меди, палладия и др. The processes of oxidation of organic and inorganic substances occupy an important place in modern chemistry and technology. It seems natural that such processes should be multifunctional and highly efficient. In addition, it is highly desirable that they occur in fairly mild conditions – the ideal conditions (while in most cases difficult to achieve) are atmospheric pressure and room temperature. Currently, most of the processes used in industry are carried out with a sufficiently high selectivity, and require correspondingly harsh conditions for their implementation (temperature above 100°C and increased pressure). In many cases, processes using bound oxygen as oxidants (permanganates, bichromates, hypochlorites, various peroxides) are more selective and less energy-intensive. However, such oxidizing agents are used only for low-tonnage products, since, as a rule, they are quite expensive and scarce. In addition, their use often leads to the formation of non-recyclable waste. Therefore, we can really consider only molecular oxygen as an oxidizer for the neutralization of NDMG, DMA, and methanol. This oxidizer is cheap, and the only waste products of the process are the oxidation products of water, nitrogen and CO2. Therefore, the search for new catalytic systems in this area is an important and interesting task. A promising class of compounds, among which similar catalysts have already been found, are compounds of transition metals, in particular, cobalt, nickel, copper, palladium, etc.

Transformation of Resinous Components of the Ashalcha Field Oil during Catalytic Aquathermolysis in the Presence of a Cobalt-Containing Catalyst Precursor

The aim of this work was to study the fractional composition of super-viscous oil resins from the Ashalcha field, as well as the catalytic aquathermolysis product in the presence of a cobalt-containing catalyst precursor and a hydrogen donor. The study was conducted at various durations of thermal steam exposure. In this regard, the work enabled the identification of the distribution of resin fractions. These fractions, obtained by liquid adsorption chromatography, were extracted with individual solvents and their binary mixtures in various ratios. The results of MALDI spectroscopy revealed a decrease in the molecular mass of all resin fractions after catalytic treatment, mainly with a hydrogen donor. However, the elemental analysis data indicated a decrease in the H/C ratio for resin fractions as a result of removing alkyl substituents in resins and asphaltenes. Moreover, the data of 1H NMR spectroscopy of resin fractions indicated an increase in the aliphatic hydrogen index during catalytic aquathermolysis at the high molecular parts of the resins R3 and R4. Finally, a structural group analysis was carried out in this study, and hypothetical structures of the initial oil resin molecules and aquathermolysis products were constructed as well.

Polymeric waste valorization at a crossroads: Ten ways to bridge research on model and complex/real feedstock

The valorization of polymeric waste, such as biomass, tires, and plastics, via thermal depolymerization (i.e., pyrolysis and liquefaction) and simultaneous or subsequent catalytic treatment has gained enormous momentum. The inherent...