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Research On The Adsorption Of Lignite Humic Acid Onto Natural Iron, Titanium And Silica Oxide Ores

Posted on:2013-01-25Degree:MasterType:Thesis
Country:ChinaCandidate:P LiFull Text:PDF
GTID:2230330374989305Subject:Mineral processing engineering
Abstract/Summary:PDF Full Text Request
Lignite humic acid pellet binder has promising development prospects for its many advantages including low addition amount, a small residual content, significantly increase effect on the iron grade of pellets, as well as the broad raw material source---lignite as a kind of poor quality coal, comparetively lower cost than other organic binders. Humic acid accounting for70to90percent of organic ingredients in this sort of pellet binder is one of the main ingredients.In this investigation, high grade humic acid was extracted and purified from lignite, and then the structure charaterization and properties of this humic acid was studied through comprehensive means including chemical analysis, Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), thermogravimetry-infrared spectroscopy (TG-FTIR) technologies. And then the adsorption behaviors as well as the adsorption mechanism of lignite humic acid onto magnetite, hematite, quartz and anatase were investigated by potentiodynamic tests and Fourier transform infrared spectroscopy (FTIR).Humic acid is a complicated organic matter with high aromatic degree mainly composed of carbon, hydrogen, oxygen, nitrogen, sulfur and other elements. The aromatic rings and various miscellaneous rings, as well as some aliphatic chains and esters, constitute the main structure of the humic acid. The bulk organic groups are carboxyl (-COOH) and phenolic hydroxyl group (-OHph), but small amounts of amino (-NH2), sulfonic (-SO3H) are also found in humic acid.350℃-650℃is the main decomposition and oxidation stage of humic acid, and the decomposition and volatile progress has basically stopped by650℃with carbon dioxide and water vapor as the main decomposition products.Solution pH has vital impact on adsorption of humic acid onto natural iron, titanium and silica oxide ores particle surfaces, and the adsorption is enhanced as pH decreasing. The adsorption degree of humic acid onto mineral particles in the alkaline system (pH=10,11), should be in the order of anatase> magnetite> hematite, while the quartz has alomost non-adsorption for humic acid. Increasing specific surfaces of mineral particles promotes the adsorption of humic acid.Micro-adsorption behavior studies have shown that the adsorption of humic acid on mineral surface forms a colloid film enveloped fine mineral particles, which therefore improves the viscosity and friction between the particles. Under certain humic acid concentration, humic acid colloids adsorbed on mineral particle surfaces adhere and unit mutually to form a net structure between fine mineral particles, and therefore fine mineral particles are coagulated.Humic acid is negatively charged under the experimental solution pH conditions (2-11) for its amounts of negatively charged functional groups, the point of zero charge (PZC) of magnetite, hematite and quartz is4.7,6.7and2.4, respectively. Under higher pH conditions (pH higher than the mineral’s PZC), humic acid adsorbs to the surface of magnetite, hematite, and anatase particle surfaces mainly by chemical reaction. While at lower pH values, hydrophobic interaction, electrostatic attraction and chemical reaction (ligand exchange and complexation) all occur and contribute to the adsorption. Specificially, hydrophobic interaction contributes more than the other two.
Keywords/Search Tags:iron ore, binder, humic acid, adsorption
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