Release Of Fine Particles Research Articles

The impact of mining on the environment in Morocco

The mining sector is one of the pillars of economic growth, although it still has a negative impact on the environment. Mines have a significant impact on the environment in Morocco, both ecologically and socially. Mining as a source of income and economic development also has crucial consequences. In environmental terms. The opening of mines often leads to the destruction of local ecosystems. From this, deforestation, biodiversity loss and habitat fragmentation are frequent consequences of mining. In addition, mineral extraction can result in air, water and soil pollution due to the use of toxic chemicals and the release of fine particles. This has disastrous effects on water quality, the health of local populations and aquatic ecosystems. Mines also have significant social impacts. Local communities may be displaced from their ancestral lands, losing their livelihoods and their connection to their natural environment. Mine workers may be exposed to hazardous working conditions and high health risks. The Moroccan government has taken measures to mitigate the environmental impacts of mines, such as adopting stricter environmental regulations and promoting more sustainable mining practices.

Health and environmental impact assessment of landfill mining activities: A case study in Norfolk, UK

The release of fine particles during mechanical landfill mining (LFM) operations is a potential environmental pollution and human health risk. Previous studies demonstrate that a significant proportion (40–80% wt) of the content of fine soil-like materials within the size range <10 mm to <4 mm recovered from such operations originate from municipal solid waste (MSW) landfills. This study evaluates the potential health risks caused by emissions from LFM activities. MSW samples recovered from the drilling of four different wells of a closed UK landfill were analysed for physical, chemical, and biological properties to determine the extent of potential contaminant emissions during LFM activities. The results show that fine particles (approximately ≤1.5 mm) accounted for more than 50% of the total mass of excavated waste and contained predominantly soil-like materials. The concentrations of Zn, Cu, Pb, Cd, As, and Cr exceed the permissible limits set by the current UK Soil Guideline Values. The highest geoaccumulation index and contamination factor values for Cu were 2.51 and 12.51, respectively, indicating a moderate to very high degree of contamination. Unsurprisingly, the pollution load index was >1, indicating the extent of pollution within the study area. The hazard quotient values indicated high exposure-related risks for Pb (16.95), Zn (3.56), Cd (1.47), and As (1.46) for allotment land use and As (1.96) for residential land use. The cancer-related risk values were higher than the acceptable range of 1.0 × 10−6 to 1.0 × 10−4. The cancer risk factor indicated that Cr and As were the major human health risk hazards.

Sulfide reduction can significantly enhance transport of biochar fine particles in saturated porous medium

The release of fine particles from biochar materials applied in the environment may have important environmental implications, such as mobilization of environmental contaminants. In natural environments biochar fine particles can undergo various transformation processes, which may change their surface chemistry and consequently, the mobility of the particles. Here, we show that sulfide reduction can significantly alter the transport of wheat-straw- and pine-wood-derived biochar fine particles in saturated porous media. Counterintuitively, the sulfide-reduced biochar particles exhibited greater mobility in artificial groundwater than their non-reduced counterparts, even though reduction led to decrease of surface charge negativity and increase of hydrophobicity (from the removal of surface O-functional groups), both should favor particle deposition, as predicted based on extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory. Using transport experiments conducted in single-cation background solutions containing K+, Mg2+ or Ca2+ under different pH conditions, we show that the surprisingly greater mobility of sulfide-reduced biochar particles was attributable to the removal of surface carboxyl groups during reduction, as this markedly alleviated particle deposition through cation bridging, wherein Ca2+ acted as the bridging agent in linking the surface O-functional groups of biochar particles and quartz sand. These findings show the critical roles of surface properties in dictating the mobility of biochar fine particles and call for further understanding of their transport properties, which apparently cannot be simply extrapolated based on the findings of other (engineered) carbonaceous nanomaterials.

A review on clogging mechanisms and managements in aquifer storage and recovery (ASR) applications

Clogging, the major obstacle in aquifer storage and recovery (ASR) applications, causes declines in recharge rates and ultimately the failure of artificial recharge systems. Clogging is generally triggered by physical processes, which involve the accumulation of suspended solids from recharge water, the release of fine particles from soils and aquifers and their migration, and the formation of gas barriers from the entrapped air in recharge water and biogenic gases. Physical clogging is then followed by biological processes (e.g., the growth of microorganisms and the accumulation of biomass). It can be further aggravated by chemical reactions leading to mineral precipitation. Prior to artificial recharge, source water can be pretreated via sedimentation, coagulation, filtration, advanced oxidation, and disinfection to lessen the clogging potential. Although such preventive measures are useful, clogging will eventually occur in recharge systems, thus necessitating the rehabilitation. The rehabilitation methods include backwashing, scrubbing, surging, jetting, under-reaming, acidification, and biociding. Notably, the methods applied vary with the type of recharge systems: surface infiltration systems, vadose zone infiltration systems, and aquifer injection wells. Among them, surface infiltration systems are most cost-effective and easiest to install and maintain. Even if field conditions are not adequate for their implementation, surface infiltration systems can be used in conjunction with the other recharge systems.

Compression dewatering of municipal activated sludge: Effects of salt and pH

Even after mechanical dewatering, activated sludge contains a large amount of water. Due to its composition and biological nature this material is usually highly compressible and known to be difficult to dewater. In the present work, two treatments (salt addition and pH modification) are proposed to highlight some aspects which could explain the poor dewaterability of activated sludge. Dewatering tests are carried out in a pressure-driven device in order to well examine both, filtration and compression stages. Physico-chemical parameters, such as surface charge, hydrophobicity, extracellular polymeric substances (EPS) content and filtrate turbidity are measured on the tested sludge, for a better analysis of dewatering results.The dewatering ability of the sludge is widely linked to the cohesion of the flocculated matrix and the presence of fine particles. Both treatments alter the flocculated matrix and release fine particles. The release of fine particles tends to clog both, the filter cake and the filter medium. Consequently, the filtration rate decreases due to higher resistances to the flow. On another hand, the polymeric matrix breakdown enables to release some water trapped within the floc to the bulk liquid phase and thus facilitates its removal, which tends to decrease the moisture content of the filter-cake. It also impacts the compression dewatering step. The more destroyed structures lead to less elastic cakes and thus a slower primary consolidation stage. At the opposite, the mobility of the broken aggregates within the filter-cake does not seem to be improved by size reduction (the kinetics of the secondary consolidation stage are not significantly modified).

Deposition and aggregation of Brownian particles in trickle‐bed reactors

AbstractWhen dilute liquid suspensions contaminated with Brownian fine solids are treated in catalytic trickle‐bed reactors, bed plugging develops and increases the resistance to two‐phase flow until ultimate unit shutdown for bed substitution with pristine catalyst is imposed. One of the important aspects during plugging with Brownian particles is the aggregation of fines and the release of the fine particles and aggregates from pore bodies within the porous bed as a result of the hydrodynamic or colloidal forces. Current physical models linking gas–liquid flow to the filtration process in high‐pressure/temperature trickle beds neglect the possible colloidal particle aggregation and the release of aggregates. This work attempts to fill this gap by developing a Euler–Euler fluid dynamic model based on the volume average mass, momentum, and species balance equations, filtration equations for the Brownian particles and the aggregates, and the discrete population balance equations for the agglomeration of particles. Both monolayer and multilayer depositions were considered for Brownian particles and only the monolayer deposition in the case of the detaching aggregates. The release of fine particles and aggregates from the collector surface was assumed to be induced by the colloidal forces in the case of Brownian particles/aggregates or by the hydrodynamic forces in the case of non‐Brownian aggregates. Brownian particle aggregation was described by the rate at which a certain size aggregate is being formed by smaller aggregates less the rate at which the aggregate combines to form a larger aggregate. © 2006 American Institute of Chemical Engineers AIChE J 2006

Use of genetic algorithms as an aid in modeling deep bed filtration

Deep bed filtration (DBF) is a very dynamic, complex process involving the capture and release of fine particles within a porous medium, dependent upon the chemistry state of the liquid phase. This paper presents a general model for permeability loss within a DBF process and then applies the model to the specific system of secondary oil recovery. The use of a genetic algorithm (GA) allows for the determination of the model parameters based on an efficient set of experimental data. GAs are optimization algorithms, based on the mechanism of natural selection. The explanation, benefits and development of the GA coding are included. The results found model the process with >97% accuracy for permeability loss up to 90%. The GA format allows for easy adaptation of this model to represent other filtration systems and further illustrates the usefulness of GAs in transport phenomena.

Coating charcoal with polyacrylate-polymethacrylate copolymer for haemoperfusion. I: Fabrication and evaluation.

A potential haemoperfusion system has been developed using activated charcoal encapsulated with a polyacrylate-polymethacrylate copolymer. The film forms a coating of great mechanical strength around the charcoal particles, which is readily permeable to water and certain dissolved substances. The charcoal granules were coated with various membrane thicknesses consisting of a 2-10 per cent (by weight) film coat, using the modified method of non-solvent addition of Benita et al. (1985). The effect of various encapsulation variables such as stirring rate, rate of addition of non-solvent, percentage of coating polymer and concentration of a non-wall-forming polymer (PIB) in the non-solvent phase on adsorptivity, as well as the release of fine particles, were determined. The effect of coating thickness on the adsorption rate of the coated charcoal was investigated by constructing Higuchi diffusion model plots using methylene blue as a model adsorbate. It was found that the membrane permeability can be adjusted by changing experimental conditions to obtain high adsorption capacity along with a low level of released particles. Further, the effect of presoaking of the coated charcoal in purified water, normal saline, and 0.067 M phosphate buffer pH 7.4 (for 24 h at 37 degrees C) on the rate of adsorption of methylene blue was also evaluated.

Polymer coating for hemoperfusion over activated charcoal.

Plasma polymerization (glow discharge) was used to make a polymeric coat with hexamethyldisiloxane on the surface of activated charcoal granules. These samples were examined with ESCA and SEM for surface chemical analysis, coat thickness, and uniformity, and for changes in surface topography. The effects of the coat on absorptive capacity and release of fine particles were examined.