Depressant Type Research Articles

Pyrite–Coal Depressants Interactions During Coal Reverse Flotation

This work investigates coal desulfurization by using reverse flotation. In this method, pyrite (the only source of sulfur in the studied coal) was separated from the meta-bituminous coal by using three different coal depressants (starch, dextrin and humic acid). A novel variable elimination approach was used to determine the contribution of the depressant type and the depressant concentration on the desulfurization performance. The results showed that the pyrite recoveries are influenced by the depressant type while the highest pyrite recovery was achieved in the presence of humic acid. Therefore, humic acid should be used in flotation rougher and scavenger cells in which the aim is to achieve high pyrite recovery. By contrast, the pyrite grades are affected significantly by the depressant concentration. Considering that the aim in flotation cleaner cells is to achieve high pyrite grade, any of the studied coal depressants can be successfully used but at high concentrations. This work demonstrated that the selection of flotation depressants depends on the type of flotation cells used in coal desulfurization.

A Study on the Effect of Ultrasound Irradiation as Pretreatment Method on Flotation of Sedimentary Phosphate Rock with Carbonate–Silicate Gangue

This research aims to explore the effect of ultrasound irradiation as a pretreatment method on the reverse flotation of phosphates. Ultrasonic treatment was used prior to flotation at various ultrasound intensities. The feed sample containing 10.34% P2O5 and 48.01% CaO was obtained from Lar mountain located in southwest of Iran. Flotation experiments were performed using two approaches: (1) a 2-level fractional factorial design with six variables and (2) try and error method. The results of experimental design showed that depressant type and pH were the effective parameters. The collected data from try and error experiments indicated that the conditioning time was the most effective parameter on the recovery. (By reducing the conditioning time from 11 to 6 min, the recovery was increased from 65.93 to 87.88%.) Furthermore, surface cleaning of phosphate minerals treated by ultrasound waves was proved by kinetic analysis, semiquantitative analysis by XRD and SEM–EDX. It was concluded that efficiency of phosphate flotation using ultrasound irradiation due to the cavitation bubbles that led to clean surface of particles is higher compared to the conventional flotation. After a cleaner step, the final grade and recovery of P2O5 reached 21.31% and 77.18%, respectively.

Optimization of Reverse Cationic Flotation of Low-Grade Iron Oxide from Fluorspar Tails Using Taguchi Method

Due to gradual depletion of high-grade iron ores, there is a need to investigate the treatment of low-grade iron ores. Current procedures are time and cost intensive. Batch laboratory scale reverse cationic flotation was employed to concentrate low-grade Fe ore, found in fluorspar tails in the form of hematite. This study used two types of depressants (soluble starch and dextrin) and two types of amines (primary mono-amine and tertiary mono-amine). Optimisation of the process investigated parameters such as pH, collector type and dosage, depressant type and dosage, conditioning time, solids content, agitation speed and air flow rate. Owing to the high number of experiments when all possible combinations are investigated, Taguchi design of experiment method was utilised to streamline the number of experiments and optimize parameters using orthogonal array and signal–noise ratio (SN). The SN was used to determine the optimum conditions and analyse the relative significance of parameters studied. The results showed that both depressants were efficient for hematite depression; however, soluble starch produced better results when compared to Betachem 30D. Both Betacol 373 and Dodecylamine collectors were efficient as quartz collectors; however, Dodecylamine produced better results when compared to Betacol 373. Ranking of parameter using SN ratio showed that pH was the most critical parameter in obtaining higher Fe grade concentrate and the optimum pH is 10. De-slimming leads to low recoveries during reverse flotation of iron ores. The main conclusion is that Taguchi method can be used to optimise a reverse cationic flotation process of a low-grade iron ore.

Optimization of Operating Parameters for Flotation of Fine Coal Using a Box-Behnken Design

In this study, experiments were carried out to examine flotation characteristics of fine coal and to determine the effect of various reagents on the coal flotation and the most optimum flotation conditions. The aim of the study was to obtain low-ash content of froth products from a high-ash-containing feed. The flotation experiments were carried out in two steps. First the optimum flotation condition parameters, such as optimal particle size, frother type, conditioning time, solid-liquid ratio, depressant type, and effect of flocculants, were determined. In the second step, keeping the optimum conditions obtained from the first step constant, a Box- Behnken design was applied for modeling and optimization of some operating variables. Three independent variables are categorized as follows: collector dosage (0–2 kg/t), frother dosage (0.1–0.3 kg/t), froth collecting time (120–180 sec). The results obtained from the experiments were subjected to multiple regression analysis by using SPSSP19. A LOQO/AMPL optimization algorithm was used for the solution of the quadratic regression models. The R2 values of the second-order regression equation for ash content of clean coal and yield were calculated as 0.905 and 0.959, respectively. This showed a good relationship between observed and calculated values. Three-dimensional graphics were created to demonstrate the dependent and independent variables behaviors.

The Aggloflotation of a Bituminous Coal-feldspar Mixture and a Bituminous Coal-quartz Mixture

The aim of this study was to investigate aggloflotation of bituminous coal-feldspar mixture and bituminous coal-quartz mixture. Experimental studies were conducted on four mixture samples. The study was performed in two groups. Conventional aggloflotation tests were made and the effects of pH and depressant type and amount on the aggloflotation were investigated in the first group experiments. The samples were first treated with sodium oleate in the second group experiments. The effects of pH and sodium oleate amount on the aggloflotation of gangue minerals were studied in order to enhance their response to aggloflotation and then the effect of different depressants on aggloflotation were investigated. The effectiveness of conventional aggloflotation on the removal of gangue minerals containing major elements from the samples were found to be important according to the performed experiments by making selective sodium oleate adsorption.

An investigation into the effect of various ions and their ionic strength on the flotation performance of a platinum bearing ore from the Merensky reef

The presence of ions in plant water is believed to be having an effect on the flotation process as ions are able to modify the chemistry of the system. This study investigated the interactive effects of ionic strength, depressant dosage and depressant type on the recovery of copper and nickel sulphides, water, floatable and entrained gangue as well as grade of the valuable sulphides in the flotation of a Pt bearing ore from the Merensky reef. Batch flotation results showed no change in Cu recovery, but Ni recovery decreased dramatically when a polysaccharide depressant was charged at 500g/t. Water recovery increased with increasing ionic strength, indicating that there exist ions in the water system which have a froth stabilising effect.

The effect of frother type and dosage on flotation performance in the presence of high depressant concentrations

The use of high dosages of polysaccharide depressants in order to depress the undesired naturally floatable gangue (NFG) present in ores beneficiated from the Bushveld Complex, South Africa, results in a significant decrease in the stability of flotation froths. These unstable froths can result in restricted mass pull and decreased valuable mineral recovery. Previous work using a single polyglycol ether type frother, DOW 200, has shown that an increase in frother dosage could be used to overcome the destabilisation of the froth to a certain extent and improve valuable mineral recovery. This resulted in an increase in water recovery and dilution of the concentrate by entrained material. This work extends this study to examine the effect of using a stronger frother, DOW 250, on the recovery of sulphide minerals and floatable gangue from a Merensky ore at different dosages of guar gum and CMC, which are typically used as depressants in the processing of Merensky ore. Results indicate that an increase in the strength of the frother resulted in a more robust froth. Depressant type also had an influence on results obtained.

The effect of the reagent suite on froth stability in laboratory scale batch flotation tests

In batch flotation tests conducted on ores from the Merensky reef, changes in froth stability invariably occur with variations in the reagent suite. The main reagents are collectors (primary and secondary), activators, depressants and frothers. Since the particles entering and leaving the froth in a batch flotation system are continuously changing, the stability of the froth can vary. Under these conditions the simplest measure of froth stability is the measure of water recovery at a fixed froth height. The batch flotation system developed at UCT allows for the separation of gangue which is entrained relative to gangue which is floated. It has been found that the presence of naturally floatable gangue (NFG) leads to froth stabilisation, whereas the presence of hydrophobic sulfide minerals may lead to destabilisation of the froth depending on the hydrophobicity (contact angle) of the sulfide minerals. This can vary with ore type since particle shape and amount of particles present can influence the extent of destabilisation. At low depressant dosages sodium isobutyl xanthate (SIBX) always results in lower froth stability than sodium ethyl xanthate (SEX). The frothing nature of dithiophosphate leads to increased froth stability and the addition of copper sulfate results in destabilised froths. Increasing depressant dosage reduces the stabilising influence of NFG and the depressant type (guar gum or CMC) also affects froth stability. Frother can be used in an attempt to overcome the destabilising effects of high depressant dosage. This work examines the effect of variations in the reagent suite and uses water recovered at a fixed froth height as an indication of froth stability in order to analyse these effects on the recovery of sulfide minerals, floatable gangue and entrained gangue.

Desulfurization and Deashing of Adiyaman-Gölbaşi Lignite by Flotation

In this study, desulfurization and deashing of Adiyaman-Gölbaşi lignite by the flotation method were studied. For this purpose, the study was performed in three groups. The effects of solid concentration, NaOH, and HCI on the desliming before flotation were investigated in the first group of experiments. The effects of some parameters that markedly influence the effectiveness of flotation, such as grinding time, solid concentration, pH, collector type and amount, depressant type and amount, and frother type and amount on the flotation were investigated in the second group of experiments. The effects of lake water and sea water on the flotation were investigated in the third group of experiments. The influences of the Aegean Sea water and soda lake water on the removal of total sulfur were found to be important.

Desulfurization and de-ashing of a mixture of subbituminous coal and gangue minerals by selective oil agglomeration

The aim of this study was to investigate desulfurization and de-ashing of a mixture of subbituminous coal and gangue minerals by the agglomeration method. For this purpose, experimental studies were conducted on a mixture containing subbituminous coal, pyrite, quartz and calcite. The effects of some parameters that markedly influence the effectiveness of selective oil agglomeration, such as solid concentration, pH, bridging liquid type and concentration, and depressant type and amount, were investigated. Agglomeration results showed that the usage of various depressants (Na{sub 2}SiO{sub 3}, FeCl3, corn starch, wheat starch) in the agglomeration medium has a positive effect on the reduction of ash and total sulfur content of agglomerates. It was found that an agglomerate product containing 3.03% total sulfur and 25.01% ash with a total sulfur reduction of 56.71% was obtained from a feed that contained 7% total sulfur and 43.58% ash when FeCl{sub 3} was used in the agglomeration medium.

The role of the reagent suite in optimising pentlandite recoveries from the Merensky reef

The Platinum group elements (PGEs) in the Merensky Reef in the Bushveld Complex are strongly associated with the sulphide minerals, particularly pentlandite which contains significant amounts of PGEs such as palladium and rhodium in solid solution. The various operations use different reagent combinations in the flotation process to recover PGEs from the Merensky Reef which include primary and secondary collectors, copper sulphate (CuSO 4) as an activator and depressants, either carboxymethylcellulose (CMC) or modified guar gum (guar). This study examines the effect on two different ores, A and B, using dibutyl dithiophosphate (DTP) as a secondary collector in combination with sodium isobutyl xanthate (SIBX) as primary collector, the point of collector addition (mill or cell), the use of CuSO 4 addition, sequence of CuSO 4 addition and the effect of depressant type on the floatability of pentlandite, and shows that pentlandite floatability in contrast to that of chalcopyrite is reduced when reagents were added to the cell rather than the mill together with CMC. This effect was not observed with the use of guar gum as the depressant.

Preclinical abuse potential assessment of the anticonvulsant zonisamide

AbstractZonisamide (Zonegran®) is a broad‐spectrum antiepileptic agent that shares some pharmacological properties with other anticonvulsants, including phenytoin, carbamazepine, and valproic acid, but is differentiated from these agents by the ability to significantly block T‐type calcium channels. Zonisamide interacts with the γ‐amino‐butyric acid (GABA) receptor in an allosteric manner, and thus does not modulate GABA receptor effects. However, given the potential of drugs within the latter class for drug abuse in humans, an evaluation of zonisamide for abuse potential is an important component of its potential side‐effect profile. In the present study, zonisamide was tested in animal models of the subjective and reinforcing effects of central nervous system (CNS) depressant drugs, e.g., diazepam discrimination in rats and intravenous self‐administration in rhesus monkeys, respectively. In addition, zonisamide was evaluated for physical dependence liability in a chronic infusion model using rats. Zonisamide did not substitute for diazepam in rats trained to discriminate 2.5‐mg/kg diazepam from vehicle nor was it self‐administered by rhesus monkeys experienced in methohexital‐reinforced responding. Continuous infusion of zonisamide (400 or 600 mg/kg/day) did not prevent the loss of body weight associated with discontinued pentobarbital infusion. These doses of zonisamide did produce some incomplete attenuation of observable signs of pentobarbital withdrawal, likely due to direct sedative or depressant effects of these high doses. These results suggest that zonisamide would not produce diazepam‐like intoxication in humans nor would it likely be subject to abuse when made more widely available. Further, when administered chronically, zonisamide would not be expected to produce physical dependence of the CNS depressant type. Taken together, these results support the prediction that zonisamide would have low abuse liability. Drug Dev. Res. 54:66–74, 2001. © 2001 Wiley‐Liss, Inc.

99/03507 Mechanisms operating in flotation froths: Ross, V. E. Recent Adv. Coal Process., 1998, 2, (II), 109–144

The use of high dosages of polysaccharide depressants in order to depress the undesired naturally floatable gangue (NFG) present in ores beneficiated from the Bushveld Complex, South Africa, results in a significant decrease in the stability of flotation froths. These unstable froths can result in restricted mass pull and decreased valuable mineral recovery. Previous work using a single polyglycol ether type frother, DOW 200, has shown that an increase in frother dosage could be used to overcome the destabilisation of the froth to a certain extent and improve valuable mineral recovery. This resulted in an increase in water recovery and dilution of the concentrate by entrained material. This work extends this study to examine the effect of using a stronger frother, DOW 250, on the recovery of sulphide minerals and floatable gangue from a Merensky ore at different dosages of guar gum and CMC, which are typically used as depressants in the processing of Merensky ore. Results indicate that an increase in the strength of the frother resulted in a more robust froth. Depressant type also had an influence on results obtained.

Joint use of metal ion hydroxy complexes and organic polymers to depress pyrite and ash during coal flotation

A novel system for the depression of pyrite and the ash-forming minerals has been developed. A metal ion, including but not restricted to Fe+2, is added to form a hydroxide coating on the pyrite or ash-forming minerals. A polymeric depressant is then added to attach to these resurfaced minerals. Nearly 200 flotation tests with 11 different coals indicate the effectiveness of this system. Many of the important process variables such as the coal source, frother-collector system, grind size and procedure, pH, metal ion, and depressant type and concentration have been studied.

Synthesis and Neurotropic Activity of 5-Substituted Furfural Thiosemicarbazones

Abstract 5-Substituted-2-furaldehyde thiosemicarbazones were prepared from furfurals and thiosemicarbazide using the condensation method. The neurotropic activity of the synthesized thiosemicarbazones has been evaluated. The majority of the compounds examined has been shown to possess high or medium neurotropic activity of the depressant type. Structure-activity relationships of the titled compounds have been studied as well.

Synthesis and neurotropic activity of silyl‐substituted fufural thiosemicarbazones

Abstract5‐Silyl‐substituted‐2‐furaldehyde thiosemicarbazones were prepared by the condensation of the corresponding furfurals or furfural diethylace‐tals with thiosemicarbazide. The neurotropic activity of the synthesized thiosemicarbazones has been studied. The majority of the compounds examined possess high or medium neurotropic activity of the depressant type. They also show antihypoxic activity and decrease the duration of phenamine stereotype behaviour. Structure‐activity correlation has been found.

Discriminative stimulus properties of toluene in the rat

Rats were trained to discriminate toluene (100 mg/kg, IP) from vehicle in a two-lever operant task. Acquisition of the discrimination required a range of 85–219 training days. Injections of either methohexital (0.5–10 mg/kg) or oxazepam (0.5–20 mg/kg) produced toluene-lever responding in a dose-dependent fashion in most animals. The discriminative stimulus properties of toluene were not found to generalize to chlorpromazine (0.3–10 mg/kg). These results are consistent with those obtained in the mouse and provide further evidence that toluene has stimulus properties similar to those of CNS depressant drugs. These results further suggest that toluene may have drug abuse potential of the CNS depressant type.

Basic amides of 2,4,5-trichlorophenoxyacetic, 2,4,6-trimethylphenoxyacetic and 4-bromo-3,5-dimethylphenoxyacetic acid and some related compounds; Synthesis and pharmacological screening

Reactions of methyl esters II of 2,4,5-trichlorophenoxyacetic (Ia), 2,4,6-trimethylphenoxyacetic (Ib) and 4-bromo-3,5-dimethylphenoxyacetic acid (Ic) with 2-diethylaminoethylamine, 2-morpholinoethylamine, 3-morpholinopropylamine, 1-methylpiperazine, 3-(4-methylpiperazino)propylamine, 3-[4-(2-tolyl)piperazino]propylamine and 1,4-bis(3-aminopropyl)piperazine in boiling ethanol gave the basic amides Va-XIc which were isolated as hydrochlorides. Reactions of the acid chlorides IVa and IVb with 1,4-bis(2-hydroxyethyl)piperazine and 1,4-bis(3-hydroxypropyl)piperazine in dimethylformamide resulted directly in dihydrochlorides of diesters XIIab and XIIIab. The compounds prepared have only weak CNS effects (mostly of the depressant type); they have local anaesthetic, mild hypotensive (some of them adrenolytic), antiarrhythmic and peripheral vasodilating activities.

PILOCARPINE-INDUCED CONVULSIONS AND DELAYED PSYCHOTIC-LIKE REACTION

The subcutaneous injection into albino rats of pilocarpine hydrochloride at doses in the range of the median lethal dose produced two types of acute toxicity syndromes, an immediate muscarinic convulsive reaction and a delayed psychotic-like reaction. The LD50±S.E. of the immediate reaction was estimated at 642 ± 90 mg per kg and that of the delayed reaction at 430 ± 126 mg per kg. The mean ± standard deviation time to death in the immediate reaction was 34 ± 20 minutes and in the delayed reaction 4.4 ± 2.5 days. The cause of death in the immediate reaction was postconvulsive respiratory paralysis following marked muscarinic activity and accompanied by hypothermia and by vascular congestion of the brain, heart, lungs, and kidneys. The muscarinic and convulsive signs disappeared in survivors by the second day and were replaced by either a depressant or excitant type of neuropsychosis characterized by disorientation and cataleptiform trances. Animals with the depressant type tended to die in hypothermic stupor with capillary vasodilatation and (or) hemorrhage and (or) other toxemic changes in many organs. Animals with the excitant type of reaction tended to survive with degrees of psychotic-like behavior persisting for a month.

Some Aspects of the Central Nervous System Activity of Urazole Derivatives II

The neurotoxicity, antielectroshock, anti-Metrazol, and antistrychnine activities of another series of urazole compounds have been determined in mice. Depending upon the nature of the substituted nitrogen groups, the members of this series, as with the previous compounds, were found to possess antielectroshock, anti-Metrazol, antistrychnine, convulsant, and depressant type actions. In general, the urazole compounds are most effective against maximal Metrazol seizures.