scholarly journals Heavy Metals as Impurities in the Bayer Production Cycle of the Aluminum Hydroxide from Sierra Leone Bauxite. Preliminary Study

2021 ◽  
pp. 151-165
Author(s):  
Gheorghe Dobra ◽  
Sorin Iliev ◽  
Lucian Cotet ◽  
Alina Boiangiu ◽  
Iosif Hulka ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Sierra Leone ◽  
Alkaline Solution ◽  
Aluminium Hydroxide ◽  
Fine Particles ◽  
Bauxite Residue ◽  
Production Cycle ◽  
Preliminary Study ◽  
Solid Phases ◽  
Mineralogical Phases

This paper is reporting the data of a preliminary study on heavy metals distribution in the fluid and solid phases involved in dry and classified aluminium hydroxide production through Bayer process. For heavy metals released in the fluid phases, the main source of contamination is the bauxite through its mineralogical phases soluble or insoluble in alkaline solution. It was shown that predominant way to transfer contaminating elements in aluminium hydroxide particles is the occlusion of very fine particles coming from mineralogical phases of bauxite residue. New born mineralogical phases from bauxite residue, like poor crystallized sodalite and cancrinite, are the most active occlusion contaminants

Understanding the factors influencing the removal of heavy metals in urban stormwater runoff

2016 ◽  
Vol 73 (12) ◽  
pp. 2921-2928 ◽  
Author(s):  
Marla C. Maniquiz-Redillas ◽  
Lee-Hyung Kim
Keyword(s):  
Heavy Metals ◽  
Fine Particles ◽  
Metal Removal ◽  
Low Impact Development ◽  
Heavy Metal Removal ◽  
Stormwater Runoff ◽  
Winter Season ◽  
Filter Media ◽  
Factors Influencing ◽  
Removal Of Heavy Metals

Abstract In this research, an infiltration trench equipped with an extensive pretreatment and filter bed consisting of woodchip, sand and gravel was utilized as a low impact development technique to manage stormwater runoff from a highly impervious road with particular emphasis on heavy metal removal. Findings revealed that the major factors influencing the removal of heavy metals were the concentration of the particulate matters and heavy metals in runoff, runoff volume and flow rates. The reduction of heavy metals was enhanced by sedimentation of particulates through pretreatment. Fine particles (<2 mm) had the most significant amount of heavy metals, thus, enhanced adsorption and filtration using various filter media were important design considerations. Sediment was most highly attached on the surface area of woodchip than to other filter media like sand, gravel and geotextile. It is suggested that maintenance must be performed after the end of the winter season wherein high sediment rate was observed to maintain the efficiency of the treatment system.

Uptake of heavy metals by some edible vegetables irrigated using wastewater: a preliminary study in Accra, Ghana

2013 ◽  
Vol 186 (1) ◽  
pp. 621-634 ◽  
Author(s):  
Michael Ackah ◽  
Alfred Kwablah Anim ◽  
Eva Tabuaa Gyamfi ◽  
Nafisatu Zakaria ◽  
John Hanson ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Preliminary Study

scholarly journals Identifying the potential of some heavy metals toxicity in urban and peri-urban cropping systems in Sierra Leone

2017 ◽  
Vol 2 (5) ◽  
pp. 74-85 ◽  
Author(s):  
Abdul Rahman Conteh ◽  
◽  
Alusaine Edward Samura ◽  
Emmanuel Hinckley ◽  
Osman Nabay ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Sierra Leone ◽  
Cropping Systems ◽  
Heavy Metals Toxicity

A Preliminary Study on the Soil Heavy Metals of Spatial Variability and Sampling Model in Field Scale

2012 ◽  
Author(s):  
Shengwei Wang ◽  
Juan Feng ◽  
Yulin Guo ◽  
Gang Liu ◽  
Juan Feng ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Spatial Variability ◽  
Field Scale ◽  
Soil Heavy Metals ◽  
Preliminary Study

A CFD Study of Existing Drag Models for Geldart A Particles in Bubbling Fluidized Beds

2014 ◽  
Author(s):  
Bahareh Estejab ◽  
Francine Battaglia
Keyword(s):  
Experimental Data ◽  
Fluidized Beds ◽  
Fine Particles ◽  
The Other ◽  
Particle Interactions ◽  
Model Group ◽  
Drag Model ◽  
Numerical Studies ◽  
Solid Phases ◽  
Drag Models

In this study, seven drag models are examined to determine how they affect fluidization behavior of Geldart A particles of biomass and coal. Notwithstanding the notable number of numerical studies to find the best drag model for larger particles, there is a dearth of information related to drag models for finer Geldart A particles. Additionally, to our knowledge, these drag models have not been tested with a binary mixture of Geldart A particles. Computational fluid dynamics was used to model the gas and solid phases in an Eulerian-Eulerain approach to simulate the particle-particle interactions of coal-biomass mixtures and compare the predictions with experimental data. In spite of the previous findings that bode badly for using predominately Geldart B drag models for fine particles, the results of our study reveal that if static regions of mass in the fluidized beds are considered, these drag models work well with Geldart A particles. It was found that the seven drag models could be divided into two categories based on their performance. One category included the Gidaspow family of drag models (Gidaspow, Gidaspow-Blend, and Wen-Yu) and the Syamlal-O’Brien drag model; these models closely predicted the experiments for single solids phase fluidization. For binary mixtures, however, the other drag model group (BVK, HYS, Koch and Hill) yielded better predictions.

Assessment of Drag Models for Geldart A Particles in Bubbling Fluidized Beds

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Bahareh Estejab ◽  
Francine Battaglia
Keyword(s):  
Binary Mixtures ◽  
Fluidized Beds ◽  
Fine Particles ◽  
Poplar Wood ◽  
Hydrodynamic Behavior ◽  
Empirical Relationships ◽  
Drag Model ◽  
Model Predictions ◽  
Solid Phases ◽  
Drag Models

In order to accurately predict the hydrodynamic behavior of gas and solid phases using an Eulerian–Eulerian approach, it is crucial to use appropriate drag models to capture the correct physics. In this study, the performance of seven drag models for fluidization of Geldart A particles of coal, poplar wood, and their mixtures was assessed. In spite of the previous findings that bode badly for using predominately Geldart B drag models for fine particles, the results of our study revealed that if static regions of mass in the fluidized beds are considered, these drag models work well with Geldart A particles. It was found that drag models derived from empirical relationships adopt better with Geldart A particles compared to drag models that were numerically developed. Overall, the Huilin–Gidaspow drag model showed the best performance for both single solid phases and binary mixtures, however, for binary mixtures, Wen–Yu model predictions were also accurate.

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