An Eco-Friendly Acid Leaching Strategy for Dealkalization of Red Mud by Controlling Phase Transformation

The alkaline components in red mud represent one of the crucial factors restricting its application, especially for the construction and building industry. The phase state of alkaline components has a significant influence on the dealkalization of red mud. In this work, an environmentally friendly acid leaching strategy is proposed by controlling the phase transformation of red mud during active roasting pretreatment. With a moderate roasting temperature, the alkaline component is prevented from converting into insoluble phases. After acid leaching with a low concentration of 0.1 M, a high dealkalization rate of 92.8% is obtained. Besides, the leachate is neutral (pH = 7) and the valuable metals in red mud are well preserved, manifesting a high selectivity and efficiency of diluted acid leaching. The calcination experiment further confirms the practicability of the strategy in the construction field, where the cementitious minerals can be formed in large quantities. Compared with the traditional acid leaching routes, the diluted acid leaching strategy in this work is acid saving with low valuable element consumption. Meanwhile, the secondary pollution issue can be alleviated. Hence, the findings in this work provide a feasible approach for the separation and recovery of alkali and resource utilization of red mud.

Solidification performances of contaminants by red mud-based cementitious paste filling material and leaching behavior of contaminants in different pH and redox potential environments

Considering the urgent need for disposal of red mud and the comprehensive treatment of coal mined-out areas, this paper presented red mud-based cementitious paste filling material (RMFM) to achieve the purpose of green filling treatment. However, the solidification performance of alkaline RMFM for contaminants can be affected when in contact with acid goaf water in practice, which may in turn causes secondary pollution to the surroundings. The leaching tests of RMFM under different pH and redox potential (Eh) conditions were designed to investigate the effects of environmental elements on the solidification performance of RMFM, and primarily investigated the treatment effectiveness of RMFM on goaf water. The test results manifest that the acidic and oxidizing environments could damage the hydration products generated by alkali and sulfate activation, thus affecting the solidification performance, while the alkaline and reducing environments could effectively prevent the release of the contaminants by enhancing the degree of alkali activation and inhibiting oxidation acid forming process. In the possible exposure environment, RMFM could effectively stabilize its own pollutants without secondary pollution. In addition, the powder RMFM samples had significant removal effects on heavy metals, the values of Cu, Pb, and As removal efficiency all reached more than 96.15%.

Research on New Cleaning Method of Automobile Air Conditioner

on the car air conditioning cleaning market at present there are some problem of cleaning method has been widely criticized, simple and convenient cleaning method, in particular, the so-called clean air conditioning is “only spray cleaner, no water washing”, this will cause the pipeline internal dirt clean is not complete, easy to internal damage other parts of automobile air conditioning, affect the normal operation of the air conditioning, the remaining part of the chemical substances will also produce secondary pollution to the air inside the car, seriously affects people’s health and safety.

A critical review on surface modified nano-catalysts application for photocatalytic degradation of volatile organic compounds

Surface modification of nano-catalyst got significant attention due its outstanding photocatalytic performance with minimum secondary pollution. Photocatalytic oxidation (PCO) is a promising technology for removing volatile organic compounds (VOCs) due...

Phytoremediation of PAHs in Contaminated Soils: A Review

Polycyclic aromatic hydrocarbons (PAHs), which are also part of persistent organic pollutants (POPs), are considered to be especially toxic to humans (carcinogenic), likewise to plants, microorganisms and other living organisms. PAHs soil contamination occurs by storage leaking, transport loss, the land disposal of petroleum waste, and accidental or intentional spills. Due to their ubiquitous occurrence, recalcitrance, bioaccumulation potential and carcinogenic activity, PAHs are a significant environmental concern. The methods of controlling and repairing PAH-contaminated soils mainly include physical remediation, chemical remediation and phytoremediation. However, there was an increasing focus on phytoremediation technologies as a result of their unique advantages, including low cost, lack of secondary pollution and large-area application. Phytoremediation is therefore one of the soil remediation technologies with the greatest potential.

Reduction of Environmental Chemicals, Toxicity and Particulate Matter in Wet Scrubber Device to Achieve Zero Emissions

When fine particles generated by the foundry industry are present in the atmosphere, they have an impact on the climate because of their influence on atmospheric radioactive phenomena. As a result of this scenario, there is a rising amount of legislation restricting the emission of pollutants from foundry industries and related businesses. In response to this situation, many researchers have concentrated on end-of-pipe technologies, one of which is the wet scrubber, which is a device that is primarily used in foundries to control pollution and is one of the devices that has been incorporated. The disadvantage of using this wet scrubber, on the other hand, is that it contributes to secondary pollution when it is used. In order to combat secondary pollution, a model of an enhanced wet scrubber system that incorporates a multi-sand filtering technology was developed. The performance of this redesigned wet scrubber system was evaluated with the use of computational fluid dynamics software. Because of the introduction of the filtration tank's computation, it was discovered that successful filtration was accomplished using sand filters, meaning that environmental chemicals and particles were totally filtered from 0.17 kg at the entrance to zero kg of particles at the outflow.

Proposing a new solution for marine debris by utilizing on-board low-temperature eco-friendly pulverization system

Developing an effective and efficient recycling process for marine debris (MD) is one of the most urgent issues to maintain environmental sustainability on Earth. However, restricted storage capacities and secondary pollution (e.g., microbial adhesion, putrefaction) limit the proper MD recycling. Here, we proposed a complete eco-friendly low-temperature MD pulverizing system that utilizes excessive liquefied natural gas (LNG) cold energy (LCE) in an LNG propulsion ship to improve the efficiency and effectiveness of MD recycling. The prototype design of the low-temperature pulverization (LTP) system showed that consumable refrigerant (liquid nitrogen) up to 2831 kg per hour could be substituted. Furthermore, with a 20% ship output, 1250 kg of MD could be treated with 363 kg of additional refrigerant. In addition, LTP systems utilizing LCE could increase the storage capacity by more than 10 times compared to bulk MD while minimizing the required energy consumption. To determine the feasibility of LTP for MD recycling, four types of plastics obtained from actual MD from a coastal area in Busan, Korea were classified and tested.

Treatment of poultry slaughterhouse wastewater using electrocoagulation: a review

Poultry slaughterhouses are generally large consumers of fresh water, which is exhausted as wastewater characterized by a high concentration of biological oxygen demand (BOD), chemical oxygen demand COD, and fats, oil, and grease (FOG). Cost-effective methods are required for the treatment of poultry slaughterhouse wastewater, with the aim of attaining a high quality effluent that can be reused in industrial processes to promote sustainability. As compared to conventional treatment methods, electrocoagulation is an efficient and low-cost system. Electrocoagulation is environmentally friendly, treating wastewater without the need of chemicals, thus limiting secondary pollution. The metal anodes initiate electrochemical reactions for coagulation and flocculation. Its distinct advantages include compact installation, and simple operation. This paper offers a comprehensive review of recent literature that has been dedicated to utilizing electrocoagulation for poultry slaughterhouse wastewater treatment. This paper also examines aspects such as theory, potential applications, current applications, as well as economical assessment of the technique.