Surface and Colloid Chemistry Flotation Chemistry PDF

SURFACE and COLLOID CHEMISTRY Prof. Dr. Orhan OZDEMIR December 2024 ▪ Flotation is a process based on separation of hydrophobic (water-repellent) particles from hydrophilic (water-wetted) particles by bubbles, and used in many industries such as waste water treatment...

SURFACE and COLLOID CHEMISTRY Prof. Dr. Orhan OZDEMIR December 2024 ▪ Flotation is a process based on separation of hydrophobic (water-repellent) particles from hydrophilic (water-wetted) particles by bubbles, and used in many industries such as waste water treatment, mineral processing and construction. ▪ Today, at least 100 different minerals (copper, lead, zinc, nickel, silver, manganese, chrome, cobalt, titanium, quartz, feldspar, and coal, etc.) are enriched using the flotation method.  Flotation Process Underground Mining Open Pit Mining Stock Area Crushing FLOAT FLOAT Transfer to Grinding FLOAT CONCENTRATE Grinding Flotation Plant Flotation Cells SINK TAILING  Introduction ▪ Flotation is a physico-chemical process exploiting differences in surface properties of minerals which depend on wettability or hydrophobicity of particle. ▪ A lot of parameters affect the success of these processes. Shape factor Roughness  Introduction Flotation In order for the flotation event to be continuous: a) In order to separate one mineral from another, the ore must be adequately ground (separation supply), b) Ensuring the continuity of the froth: In order for the flotation event to be continuous and uniform, frother is added to the medium and froth formation is achieved by mixing it mechanically. By adding flotation reagents to the medium, it is ensured that mineral particles are captured by air bubbles and brought to the surface. In order for the flotation event to be continuous: c) The medium where mineral particles attach onto air bubbles must be continuous. The particles that can easily float in flotation are those that have hydrophobic properties. In order to float the mineral particle that does not float, if the particle is not naturally hydrophobic, its surface is changed (Collector). Otherwise, it is necessary to make hydrophilic if the particle is to be sinked.  Washing Column Flotation Air Typical Denver water Concentrate Fr Flotation System Froth Froth ot h Fro th Feed Concentrate Pulp Pulp Air or Impeller air/water in Tailing Microcel Flotation Column Jameson Cell  Hydrophobic particles Air bubbles Hydrophilic particles Small particles Bubbles  Flotation Chemistry ▪ In general, minerals do not have surface properties to attach to bubble if they are hydrophilic (zero or close to zero contact angle). ▪ The enrichment of minerals with the flotation method depends on making mineral surfaces the hydrophobic selectively, the pH of the environment, and the appropriate size of air bubbles. ▪ As a result, chemicals added to the flotation medium to perform the flotation process are called flotation reagents.  Flotation Reagents ▪ The reagents used in flotation are collected in three main groups: ▪ Collectors ▪ Frothers ▪ Control reagents: ▪ Activators ▪ Depressants ▪ pH regulators ▪ others  Flotation Reagents ▪ The substances used to make the minerals attach to the bubble are called collectors. ▪ Since foam formation in a single phase liquid is not possible, frother the reagents which are called frothers are used for foam formation and increase the durability of the foam. The main rules of the operation Air Air Bubble-particle Number of Air attachment efficiency bubbles Air Liquid film Air Bubble Mineral Surface Repulsion Air Air  Flotation Reagents ▪ Various reagents are used in flotation systems called activators and depressants, which facilitate the reaction of the collecting reagents with the desired minerals and makes it difficult to react with others, respectively. ▪ Dispensers are another class of reagents used in flotation to prevent mineral particles from being covered with slam in pulp. ▪ The buoyancy of the bubble must be greater than the gravity force. ▪ The large contact angle makes mineral float easier. ▪ Thus, the flotation recovery increases. ▪ By increasing the contact angle with the collectors, it becomes stronger to hold the air bubble to the mineral. ▪ In this respect, the contact angle is a measure of the suitability of a mineral for flotation. ▪ For a good flotation, the contact angle should be 50o < θ < 75o. ▪ Flotation reagents include polar and / or non-polar groups. ▪ The non-polar group (hydrocarbon chain) is expressed as a hydrophobic group since it interacts very low with water molecules. ▪ The polar group is expressed as a hydrophilic group since it interacts strongly with water water molecules. Molecular structure of sodium oleate  Hydrophobic part Hydrophobic part Hydrophobic part Anionic part Cationic part Anionic part Mineral Surface Mineral Surface Mineral Surface (a) (b) (c) (a) Adsorption of anionic collector on positive charged mineral surface (Physical adsorption) (b) Adsorption of cationic collector on negative charged mineral surface (Physical adsorption) (c) Adsorption of anionic collector on negative charged mineral surface (Chemical adsorption) Bubble-Particle Attachment Time Experiments Bubble-Particle Attachment Time Experiments Bubble Particle Attachment Experiments  Results for Bubble-Particle Attachment Time Measurements 1.10-5 M 5.10-5 M 1.10-4 M (100 ms) (100 ms) (100 ms) ▪ As seen from the pictures, the amount of particles attached on the bubble surfaces increases with the increasing SDS concentration.  Results for Bubble-Particle Attachment Time Measurements and Flotation Experiments 100 3000 Flotation Recovery Flotation Recovery Bubble-Particle Attachment Time (ms) Bubble-Particle Attachment Time 2500 80 Flotation Recovery (% ) 2000 60 1500 40 1000 20 500 ~2-4.10-5 M SDS 0 0 1.E-05 1.10-5 1.E-04 1.10-4 SDS Concentration (M) ▪ As seen from the figure, there is a strong correlation between flotation recovery and bubble-particle atachment time.  Effect of Bubble Size on Bubble-Particle Attachment Time Measurements 2 mm 1 mm 0.5 mm 1.10-5 M SDS (100 ms) 1.10-5 M SDS 1.10-5 M SDS (100 ms) (100 ms) ▪ As seen from the videos, the amount of particles attached on the bubble surfaces increases with the decreasing bubble size.  Quartz (38×20 µm)-DAH (1.10-5 M) Bubble-Particle Attachment Time Measurements 2 mm 1 mm 0.5 mm 2 mm 1 mm 0.5 mm 1 ms Contact Time 10 ms Contact Time 2 mm 1 mm 0.5 mm 2 mm 1 mm 0.5 mm 100 ms Contact Time 1000 ms Contact Time  Quartz (38×20 µm and 20×10 µm)-DAH (1.10-3 M) Bubble-Particle Attachment Time Measurements at 0.5 mm Capillary size at 10 ms Contact Time Quartz (38×20 µm) + DAH Quartz (20×10 µm) + DAH  Quartz (38×20 µm) Bubble-Particle Attachment Measurements Quartz-DAH (1.10-3 M)  Flotation Technic ▪ Before carrying out the flotation experiments, some parameters such as; Q K: Q: Quartz (SiO ) 2 ▪ Mineralogical analysis of ore, KuvaO ) 3 Ma: Magnetite (Fe O ) H: Hematite (Fe O ) 2 3 3 4 ▪ Liberation degree, Ma ▪ What reagents to use, Q Q H ▪ To determine the required time, for adsorption of reagents on mineral surfaces (conditioning) ▪ and, pulp solids ratio ▪ are determined in the laboratory. ▪ Hallimond tube which is a micro-flotation unit made of glass is used to observe the behavior of mineral praticles in dynamic environment. Hallimond Flowmeter Tube Water Level Floating Particles pH Meter Float Sink Sinking Particles Magnetic Air Mixer Matos et al, 2019.  Micro-flotation Cell Experiments 40 mm 220 mm Air 20 mm Mikro-f lotasyon Micro-flotation cell Manometre Flowmeter hücresi Köpük Float particles toplama kabı Hava Air Tankı Source Sink Magnet Manyetik balık Flowmeter Debimetre Magnetic Manyetik Mixer karıştırıcı  Denver Flotation Experiments ▪ Denver flotation equipment is the most commonly used flotation device in laboratory trials having the flotation cells with a volume of 1, 2 or 4 liters. ▪ Conditioning is performed inside the cell and then air is supplied.  Denver Flotation Experiments ▪ Minerals floating and collected in the froth zone (at the top of the cell) are scraped off the top of the cell along with the froth. ▪ Generally, 4 or 5 concentrates are collected at different time periods. ▪ 0-1 min., ▪ 1-2 min., ▪ 2-4 min., ▪ 4-8 min., ▪ 8-16 min. ▪ The float and sink products are dried, weighed, and the chemical analyses for these products are performed.  Denver Flotation Experiments 100 100 ∑ Recovery (%) ∑ Recovery (%) 0 0 Flotation Time (min.) Tenör Feed Grade Concentrate Grade Collector Cum. Flotation Dosage Recovery (g/ton) (%) 100 50 16.40 Cumulative Flotation Recovery (%) 100 58.66 80 200 78.99 300 84.37 60 40 20 pH=8 0 0 100 200 300 400 Collector Dosage (g/ton)  Batch Scale Flotation Experiments Chemical analysis of water used in flotation processs pH Ca2+ K+ Mg2+ Na+ SO42- Cl- mg/L mg/L mg/L mg/L mg/L mg/L 7.5 554 1370 2650 25600 11300 38500 Batch Scale Flotation Experiments Concentrate I Concentrate II Sink Pilot Scale Flotation Experiments  Flotation Kinetics Chalcopyrite CuFeS2 Bornite Cu2S(Fe,Cu)S Concentrate 1 Concentrate 2 Concentrate 3 Tailings  Next Week DATE LESSON / LAB 03 January, 2025 Lesson 7: Coagulation / Flocculation 10 January, 2025 Lesson 8: Rheology / Summary 10 January, 2025 Lab Compensations