Effect of surfactant on urease-producing flora from waste activated sludge using microbially induced calcite precipitation technology to suppress coal dust

Evaluation of dust fixation effect of urease-based biological dust suppressant and its field application

Widespread mining of open-pit coal mines has led to severe dust pollution, which degrades air quality and affects human health. Due to the drawbacks of existing dust suppression methods, there is an urgent need to develop a biological dust suppressant, which is based on urease-induced carbonate precipitation and has excellent potential for application in the field of dust management. The research developed a biological dust suppressant based on urease-induced carbonate precipitation technology. By using biological dust suppressant with different ureases, the dust suppression effect was determined and field applications were conducted. The optimal formulation of the dust suppressant was identified through experiments, and the evaluation of erosion resistance, calcium carbonate yield, hardness, permeability resistance, and crust thickness was conducted, elucidating the consolidation mechanism. After synthesizing the economic benefits and treatment effects of field use, it was found that the optimal ratios of the dust suppressant were 1.0 mol/L for urea and calcium chloride, 100 g/L for soybean flour, and the ratio of urease solution and cementing solution was 1:1 when used; the calcium carbonate yield of the specimen treated by EICP (SCU) was as high as 7.49 %. In an alternative phrasing, after undergoing tests for resistance to wind and rain erosion, the mass loss rates were recorded at 0.24 g m-2·min-1 and 156.51 g m-2·min-1. When compared to the treatment with pure urease, there was a significant improvement in wind erosion resistance by 90 % and in rain erosion resistance by 25.53 %. Field applications have revealed that the distribution of calcium carbonate is uneven and exhibits a positive correlation with hardness, penetration resistance, and the thickness of the crusts formed. This is due to the macromolecular organic matter in crude urease, which not only can form a spatial mesh structure and play a bonding role, but also can provide nucleation sites for urease-induced production of calcium carbonate, promoting the precipitation and aggregation of calcium carbonate, so that the strength is improved.

Biotechnological potentials of surfactants in coal utilization: a review

The quest for scientifically advanced and sustainable solutions is driven by growing environmental and economic issues associated with coal mining, processing, and utilization. Consequently, within the coal industry, there is a growing recognition of the potential of microbial applications in fostering innovative technologies. Microbial-based coal solubilization, coal beneficiation, and coal dust suppression are green alternatives to traditional thermochemical and leaching technologies and better meet the need for ecologically sound and economically viable choices. Surfactant-mediated approaches have emerged as powerful tools for modeling, simulation, and optimization of coal-microbial systems and continue to gain prominence in clean coal fuel production, particularly in microbiological co-processing, conversion, and beneficiation. Surfactants (surface-active agents) are amphiphilic compounds that can reduce surface tension and enhance the solubility of hydrophobic molecules. A wide range of surfactant properties can be achieved by either directly influencing microbial growth factors, stimulants, and substrates or indirectly serving as frothers, collectors, and modifiers in the processing and utilization of coal. This review highlights the significant biotechnological potential of surfactants by providing a thorough overview of their involvement in coal biodegradation, bioprocessing, and biobeneficiation, acknowledging their importance as crucial steps in coal consumption.

Effectiveness and mechanism of microbial dust suppressant on coal dust with different metamorphosis degree

The extraction of coal from open-pit mines significantly contributes to environmental degradation, posing grave risks to human health and the operational stability of machinery. In this milieu, microbial dust suppressants leveraging microbially induced carbonate precipitation (MICP) demonstrate substantial potential for application. This manuscript undertakes an exploration of the dust mitigation efficiency, consolidation attributes, and the fundamental mechanisms of microbial dust suppressants across coal dust samples with varying metamorphic gradations. Empirical observations indicate that, in resistance tests against wind and rain, lignite coal underwent mass losses of 7.43 g·m-2·min-1 and 98.62 g·m-2·min-1, respectively. The production of consolidating agents within the lignite dust, attributable to the microbial suppressants, was measured at 0.15 g per unit mass, a value of 1.25 and 1.07 times greater than that observed in bituminous coal and anthracite, respectively. Scanning electron microscopy coupled with X-ray energy-dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD) analyses illuminated that the consolidating products within the coal dust predominantly constituted calcite and vaterite forms of calcium carbonate. The consolidation mechanism of coal dust via microbial suppressants is articulated as follows: Subsequent to the application on coal dust, the suppressants induce the formation of carbonate precipitates with inherent adhesive properties. These carbonates affix to the surfaces of coal dust particles, progressively encapsulating them. Furthermore, they play a pivotal role in bridging and filling the interstices between adjacent dust particles, thereby culminating in the genesis of a dense, cohesive mass capable of withstanding erosive forces.

Microscopic deposition-property relationships in microbial-induced consolidation of coal dusts

In recent years, the preparation of new microbial dust suppressants based on microbial induced carbonate precipitation (MICP) technology through enriched urease-producing microbial communities has become a new topic in the field of coal dust control. The deposition of CaCO3 was the key to suppress coal dust. However, deposition characteristics in the field is not sufficient and the relationship between deposition characteristics and erosion resistance is not clear, which hinders the development of engineering application of new microbial dust suppressant. Therefore, based on X-CT technology, this paper observed and quantified micro-deposition of bio-consolidated coal dust with different calcium sources. Furthermore, a conceptual framework for deposition was proposed and its correlation with erosion resistance was revealed. The results showed that CaCO3 induced by calcium chloride and calcium lactate was aggregate deposited. Aggregate deposited CaCO3 was small in volume, showed the distribution of aggregation in the central area and loose outside, and mosaiced pores. CaCO3 induced by calcium nitrate was surface deposition due to attached biomass. Surface deposition was mostly large volume CaCO3 expanding from the inside out, which could cover coal dust to a high degree and completely cemented pores. In addition, the threshold detachment velocity of coal dust cemented by surface deposition was increased by 17.6-19.1% compared to aggregate deposition. This depended on the abundance and strength of CaCO3 bonding between coal dust particles under different deposition. The two-factor model based on porosity and CaCO3 coverage can well express relationship between erosion resistance and depositional characteristics. Those results will help the engineering application of MICP technology in coal dust suppression.