Impact of distilled water dealkalization on the geotechnical behavior of red mud

A shift in particle size distribution toward smaller particle sizes has been observed in batches of Compound A Triethanolate, an isolated intermediate of a commercially available active pharmaceutical ingredient, leading to poor deliquoring of the filter cake and longer filtration times, which compromised the overall process cycle time. In the most extreme case, product breakthrough during filtration was observed, leading to significant yield loss. Compound A Triethanolate is crystallized through antisolvent addition/distillation/cooling crystallization in ethyl acetate/water/ethanol. Laboratory experiments were carried out using representative product streams in order to identify the cause for the shift in particle size distribution, which could be attributed to excessive secondary nucleation at an early stage of the process caused by the use of seed particles that have been previously dried under agitation. While statically dried particles exhibit a smooth surface, the surface of particles dried under a...

Particle grouping, a new method for reducing emission of submicron particles from diesel engines

The effect of CMP process parameters (pressure and pad hardness) on the ceria and silica abrasive particle-size distribution (PSD), morphology, and surface composition when polishing oxide and nitride surfaces was investigated in detail. The PSD was observed to shift post-CMP, with ceria and silica exhibiting a decrease and increase, respectively, in the number of particles towards the tail end of the distribution. The shift in ceria PSD was observed to increase as pad hardness increased. An increase in polish pressure and work surface hardness resulted in an equivalent shift in the PSD when polished on a soft pad. The inclusion of an additive reduced the oxide removal rate, and the abrasive particles exhibited the presence of a thin organic coating on the surface. The difference in material removal mechanisms and selectivity when polishing oxide and nitride with ceria and silica-based slurries was also investigated in detail.

Abstract. Nanoparticles emitted from road traffic are the largest source of respiratory exposure for the general public living in urban areas. It has been suggested that adverse health effects of airborne particles may scale with airborne particle number, which if correct, focuses attention on the nanoparticle (less than 100 nm) size range which dominates the number count in urban areas. Urban measurements of particle size distributions have tended to show a broadly similar pattern dominated by a mode centred on 20–30 nm diameter emitted by diesel engine exhaust. In this paper we report the results of measurements of particle number concentration and size distribution made in a major London park as well as on the BT Tower, 160 m aloft. These measurements taken during the REPARTEE project (Regents Park and BT Tower experiment) show a remarkable shift in particle size distributions with major losses of the smallest particle class as particles are advected away from the traffic source. In the Park, the traffic related mode at 20–30 nm diameter is much reduced with a new mode at <10 nm. Size distribution measurements also revealed higher number concentrations of sub-50 nm particles at the BT Tower during days affected by higher turbulence as determined by Doppler Lidar measurements and are indicative of loss of nanoparticles from air aged during less turbulent conditions. These results are suggestive of nanoparticle loss by evaporation, rather than coagulation processes. The results have major implications for understanding the impacts of traffic-generated particulate matter on human health.

Almost three decades on, the negative environmental impacts arising from the burning of over 600 oil wells in Kuwait following the 1991 Gulf War are still evident. At the time of the incident, the Kuwaiti desert region became polluted with hydrocarbon, with a number of ‘oil lakes’ forming, causing critical harm to local land. This paper discusses the shifts in particle size distribution (PSD) found in soil taken from Kuwait’s Al-Ahmadi oil field, caused by aging sandy soil polluted with hydrocarbon. The analysis of changes in PSD was achieved using 16 contaminated and uncontaminated soil samples, with the samples undergoing PSD analysis along with Unified Classification Soil System (UCSS), Scanning Electronic Microscopy (SEM) and Gas Chromatograph Mass Spectrometer (GC-MS) analyses.The analyses revealed a significant reduction in the mean values of both sand and silty/clay particles, which fell from 44.6% to 9.0% and 7.8% to 3.4%, respectively. The analyses also showed a significant increase in the mean values of gravel particles, rising to 44.6% from 6.1%. These results obviously clarify that the overall outcome of the alteration in soil gradation was a poorer one, which may be due to bigger particles forming out of fine particles as a result of oil contamination. The results presented in this paper are intended to support the treatment (soil washing and cement stabilisation) of contaminated sandy soil based on the insights gained into how soil grain size distribution is impacted by oil contamination.

Applying slurry to arable land as fertilizer increases the risk of phosphorus (P) runoff and thereby increases the risk of eutrophication. Solid-liquid separation can reduce the excess application of P, and this study focused on the use of ozonation as an alternative chemical pretreatment for separation to improve P separation efficiency. Sow and cattle slurries were separated by screw press and flocculation+filtration. The screw press and flocculation liquid fractions and raw slurries were treated with no ozone or with low-, medium-, or high-ozone doses and then separated by centrifugation. The pH, particle size distribution, dry matter, and dissolved phosphate (PO) concentrations were measured. For separations without ozonation, pH increased by 0.15 to 0.87 pH units, and correlation analysis showed that the dissolved PO concentration decreased with increasing pH and particle removal efficiency. During ozonation, pH increased, and a shift in particle size distribution in the liquid fraction combined with an improved dry matter separation indicated particle aggregation. Ozonation thus affected the parameters found to affect dissolved PO separation, and at the highest ozone dose, dissolved PO separation efficiency increased by 7 to 81%. An ozonation pretreatment may therefore promote removal of dissolved PO from the liquid fraction during separation.

Benthic trawling has a recognised impact on sediment whole organism communities, yet little is known about its impact on sediment biogeochemistry. On 2 cruises in October 2001 and July 2002, we measured sediment characteristics (particle size distribution, porosity and organic matter (OM)) and sediment metabolism (oxygen uptake, denitrification, sulphate reduction and sediment- water nutrient exchange) along gradients of trawling activity at 14 sites in 2 regions of the southern North Sea: one with low tidal disturbance but high trawling disturbance (Outer Silver Pit, OSP), the other with high tidal disturbance but lower trawling disturbance (Thames). There was no measurable impact of trawling activity on oxygen uptake, denitrification or nutrient exchange in either region. In contrast, at the high trawling disturbance sites in the OSP only, there was both a shift in particle size distribution (towards fines) and a greater rate of sulphate reduction (volume specific rates 0.83 and 0.49 nmol SO4 2- cm -3 h -1 at high and low impact sites, respectively), but not in the Thames. In addi- tion, areal rates of sulphate reduction were positively correlated with both silt content (i.e. associated with organics) and long-term trawling in the OSP but not in the Thames. Biogeochemical processes in the upper layers of sediment, both oxic and suboxic, seemed unaffected by trawling in the long- term. In deeper anoxic sediment, however, mineralisation via sulphate reduction may be stimulated by the extra disturbance, at least in areas where tidal energy is slight.

The present study aims to address the effect of the uniformity of particle size distribution on Pt stability. A theoretical model based on the chemical reactions of Pt oxidation and precipitation in the membrane is presented. The incorporation of a particle size distribution function and a population balance allows the investigation of different initial particle size distributions. Initial results demonstrate the change of platinum ions concentration across the electrode and membrane and reveal the shift of particle size distribution towards larger diameters under potential hold and potential cycling simulations.

Binder jetting additive manufacturing (AM) can print complex structures in economical and scalable manner. Binder jetting AM comprises of deposition and weak binding of particles, known as green part, at room temperature and subsequent binder removal and sintering densification at high temperatures. However, during the densification (i.e., sintering), the part significantly deforms due to volume shrinkage. The deformation during sintering is difficult to predict, which prevents the widespread application of this technology. In this research, powder spreading simulation using discrete element method (DEM) was performed first to capture local variations in powder bed configuration. Second, finite element method (FEM) with a phenomenological continuum constitutive model was used to predict part shrinkage during the sintering process. DEM simulation showed variations in packing density, particle segregation, formation of uneven powder bed surface, and shift in particle size distribution (PSD). The sintering simulation modeled part deformation with a reasonable accuracy of 3% for solid-state sintering and intermediate liquid phase sintering. A demonstration case with non-uniform initial packing density showed that inhomogeneous green part density and PSD should be accounted for prediction of part deformation in binder jetting AM.

These days the construction industry is fully developed due to a massive increase within a short period of time in the use of cement and concrete for multiple construction activities. The same rate is expected to continue in the next decade and this may cause global environmental impacts. The raw materials needed to manufacture cement and produce concrete provide less and require more energy for production. This increasing demand is causing a rapid depletion of resources. To overcome this situation, it is very important to use industrial waste and by-products for the manufacture of cement and concrete construction. Red mud is the extensive amount of industrial waste generated during the production of alumina. It has been found that for every 1 ton of alumina 1.2 to 1.3 tons of red mud waste is generated. As red mud has complex properties, the disposal process becomes quite challenging Disposal of this waste was the first prime problem encountered by the alumina industry after the adoption of the Bayer process. The conventional method of disposal of the red mud in ponds has often adverse environmental impacts as during monsoons the waste may be carried by run off to the surface water courses and as a result of percolating may cause contamination of ground water. Further disposal of large quantities of red mud dumped, poses increasing problems off storage occupying a lot space over the years many attempts have been made to find a use for red mud but nobody have proven to be economically satisfactory. Red mud or red sludge is a waste product generated in the industrial production of Aluminum via Bayer’s process of refining bauxite enrooted to alumina. With about 150 million tons (Globally) & 9 million tons in India of this hazardous material produced annually, red mud is one of the most important disposal problems in the mining industry. In this study, Mix was designed for M25 grade of conversational concrete. 6 mix were made in which Red mud were substituted by weight of cement in varying proportion 0%, 5%, 10% ,15%,20% and 25%. We evaluated the strength of concrete by performing tests which are compressive strength, flexural strength at the age of 7days and 28day. Study results revealed that 15% cement can be the optimally replaced by red mud beyond which compressive strength, Flexural strength deceasing. We find out that Compressive strength increase by 3.80 %, Flexural strength increase by 9.42% and replacing cement with red mud at 15%. However, the optimum level was observed as 15% without deceasing in strength. Study results revealed that 15% cement can be the optimally replaced by red mud beyond which compressive strength, Flexural strength deceasing. We find out that Compressive strength increase by 3.80 %, Flexural strength increase by 9.42% and replacing cement with red mud at 15%. However, the optimum level was observed as 15% without deceasing in strength.

Current management for red mud is insufficient and a new method is needed. A series of experiments have been carried out to develop a new approach for effective management of red mud. Mortars without or with 3%, 6% and 9% red mud were prepared and their fresh and hardened properties were measured to access the possibility of recycling the red mud in the production of red cement-based mortar. The mechanisms corresponding to their mechanical performance variations were explored by X-ray powder diffraction and scanning electron microscopy. The results show that the fresh mortars with red mud present an increase of viscosity as compared with the control. However, little difference is found when the content of red mud is altered. It also can be seen that red mud increases flow time and reduces the slump flow of the mortar. Meanwhile, it is found that mortar with red mud is provided with higher air content. Red mud is eligible to adjust the decorative mortar colour. Compressive strength of mortar is improved when less than 6% red mud is added. However, overall it has a slightly negative effect on tensile bond strength. It decreases the Ca(OH)2 content and densifies the microstructure of hardened paste. The heavy metal concentrations in leachates of mortars with red mud are much lower than the values required in the standard, and it will not do harm to people's health and the environment. These results are important to recycle and effectively manage red mud via the production of red cement-based mortar.

Red mud is a type of solid waste generated during alumina production from bauxite, and how to dispose and utilize red mud in a large scale is yet a question with no satisfied answer. This paper attempts to use red mud as a kind of additive to modify the limestone. The enhancement of the sulfation reaction of limestone by red mud (two kinds of Bayer process red mud and one kind of sintering process red mud) are studied by a tube furnace reactor. The calcination and sulfation process and kinetics are investigated in a thermogravimetric (TG) analyzer. The results show that red mud can effectively improve the desulfurization performance of limestone in the whole temperature range (1,073–1,373K). Sulfur capacity of limestone (means quality of SO2 which can be retained by 100mg of limestone) can be increased by 25.73, 7.17 and 15.31% while the utilization of calcium can be increased from 39.68 to 64.13%, 60.61 and 61.16% after modified by three kinds of red mud under calcium/metallic element (metallic element described here means all metallic elements which can play a catalytic effect on the sulfation process, including the Na, K, Fe, Ti) ratio being 15, at the temperature of 1,173K. The structure of limestone modified by red mud is interlaced and tridimensional which is conducive to the sulfation reaction. The phase composition analysis measured by XRD of modified limestone sulfated at high temperature shows that there are correspondingly more sulphates for silicate and aluminate complexes of calcium existing in the products. Temperature, calcium/metallic element ratio and particle diameter are important factors as for the sulfation reaction. The optimum results can be obtained as calcium/metallic element ratio being 15. Calcination characteristic of limestone modified by red mud shows a migration to lower temperature direction. The enhancement of sulfation by doping red mud is more pronounced once the product layer has been formed and consequently the promoting effect of red mud becomes greater once the sulfation reaction becomes diffusion controlled. This study indicates that red mud from alumina plant is a favorable additive for improving the desulfurization performance of limestone, and the effect of red mud on limestone’s desulfurization activity is due to superposition of improvement in solid-state ionic diffusion and surface chemical reaction.

Bauxite residue or red mud is the iron-oxide rich waste produced when bauxite ore is processed by the Bayer’s process to extract aluminum. Red mud characteristics and production depend on origin, quality and composition of bauxite. Storage and disposal of red mud is the biggest problem faced by the aluminum industries. Red mud residue is associated with being chemically basic, high in heavy metals and low level of naturally occurring radioactive materials. The objective of this study was to characterize red mud which is collected from Hindalco, Belgaum, on the basis of traditional geotechnical methods that may contribute to the behavior of the material and to analyze the chemical constituents of its leachate which helps to understand the leachate characteristics. The characterization of the material included index properties like moisture content, specific gravity, grain size distribution, liquid limit, plastic limit and their indices, engineering properties like shear strength by cohesion intercept and angle of internal friction, compaction characteristics by OMC and MDD and chemical properties by SEM, XRD and TCLP. The findings, in terms of leachate characteristics, showed that red mud has undergone reactions during the leaching process giving leachate with sodium, silica and calcium in highest concentration. Red mud shows acceptable characteristics for potential reuse as a civil engineering material.

Evaluation of red mud as a polymetallic source – A review

Large amount of industrial wastes are generated from various factories in India and are simply being disposed without any major applications. Alternative materials are to be adopted as a construction material so as to minimize the use of natural resources. Red mud (RM) is generated as a waste material during the production of alumina from bauxite, and it comes to around 40% of the bauxite used for the production. The paper presents the possibility of using red mud as a stabilizing material. The study examines the effect of red mud on behavior of clays by carrying out compaction test, CBR tests, and UCC tests for different percentages of red mud. The red mud soil mix is further treated with lime to understand whether more soil can be replaced by red mud on lime treatment. It was seen that the highest maximum dry density (MDD), UCS, and CBR values were obtained for 15% red mud in soil. On further treatment with 2% of lime, 20% red mud in soil showed more strength compared to 15% red mud in soil ensuring that more soil can be replaced by red mud on treating with lime.