55 Temperature centigrade Hardness Palkal- M alkal- ilica as Temperturentignity as intey as as Ca00, CaCO0 CaCOI S- 88 76 108 16 30.------------------- 72 60 100 8 60 48 92 83 60 o0 ...-------- . It Is, therefore, quite possible that the silica removal is the result of the formation of a compound such as [Mg(OH) 2]X (MgSJO3],.t [HO] 0 Some of the data appears to indicate that the removal of silica from solution by means of magnesium oxide is in accordance with an adsorption reaction. & Terms of Use. After the washing is completed, sn dbescriptio n an d conidein an the fasr Sisnot necessary to dry this precipitate, but in- going description, and considering all of the fac-ally sted m to emain In the slurry s nvolved, is that silica is most et onomscall stead it removed from solution for ind. Thus, natural water and brines, such as are obtained from salt lakes and wells, are uniformly considered as cornm- 15 prising two entirely different raw materials, substances or liquids. ations of 80-120 P. P. M., a ratio of approxiately 7.5 Parts or more of magnesium oxide per Lrt of silica is required with initial relatively w silica concentrations of 5-20 P. P. M. OI Lramount Importance is the fact that, in order obtain effective removal of silica from solution * means of any magnesium salts, it is necessary at the Precipitation of magnesium hydroxide effected In situ. Research on âhigh-pH precipitation treatmentâ for RO concentrate minimization and salt recovery in a municipal groundwater desalination facility, âHigh-pH softening pretreatmentâ for boron removal in inland desalination systems, Optimization of silica removal with magnesium chloride in papermaking effluents: mechanistic and kinetic studies, Selective removal of silicic acid by a gallic-acid modified resin, Wastewater Treatment and Reclamation: A Review of Pulp and Paper Industry Practices and Opportunities, Deinking of different furnishes of recycled MOW, ONP, and OMG pulps in silicate-free conditions using organic complex of PHASS, Silica removal with sparingly soluble magnesium compounds. For the most efficient silica removal, the hydration, or slaking, reaction should not occur in the slurry tank and transfer lines but should occur after the slurry reaches the downstream reactor. This elimination takes place according to the following reactions: COMPARATIVE DATA ON COMMERCIAL FACTORS INVOLVED TABLE VI 50 S55 Test 1-Using U. ing tables to show the relationship between the silica remaining. Privacy Policy It has been found that the addition of magnesium oxide to water in a chemical mixing tank requires approximately one-half hour for the hydrolysis, so that if the magnesium oxide remains in contact with the water in the chemical mixing tank for a period of time greater than one-half hour, and the mixture is then fed to the water to be treated, a proper efficiency for silica removal will not be obtained. 6). This report focuses on the use of MgO for thermal enhanced oil recovery systems in Alberta. Since silica becomes part of the magnesium precipitant, some means of adding already precipitated magnesium (magnesium oxide) or of precipitating magnesium "in situ" (as Mg(OH) 2) is used. Pre-acidification of the magnesium compounds increased the dissolved magnesium content, and, thus, silica removal: a 86% silica removal was obtained with both MgO and Mg(OH) 2 and a 80% with (MgCO 3) 4 â Mg(OH) 2 â 5H 2 O. oxide.) also offers the vantage of effecting a greater and espeae s ofers he va .tha n does agnesm use of magnesium oxide in the form of the reladegree o 5 n m tod simf reemov ddisoaediu dgcarbonate in dr form, as indicated the ac- tively purer and lighter weight forms of commercarona in - f , as cial magnesia; that this process functions best at companying Table Mhigh temperatures as for instance at approxiTABiE VII p. P. M. I mately 95. and 100 P. P. M., and the P alkalinity CaCOS CS0O, Ca(Oa 003 40 being between 15% and 85% of the M alkalinity - - and then separating the precipitate from the p.p.M. The method of removing dissolved silica 0.1------ 7. If the main aim is silica removal, the most efficient coagulants are PAC-HB in DAF1 and PAC-MB in DAF2. 6H2O was selected as magnesium source to analyze the effect of pH, dosage, temperature, and contact time on silica removal. They are magnesium bicarbonate, magnesium chloride, magnesium sulfate, iron sulfate, and iron chloride. By adding first 20 P. p.-M., and then 40 P. P. U. of sodium hydroxide, the hardness was substantially further reduced, but with a sharp increase in alkalinity the efficiency of the silica removal was lessened, which was consistent with the results shown in Table II. However, as Le cost of magnesium oxide is to a large degree controlling factor in the treatment of water for lica removal for industrial purposes, it is not enerally considered commercially feasible to use ie U. S. P. light magnesium oxide because of its elatively high cost, especially when the so-called ommercial and but slightly less pure magnesia is onsiderably less expensive, and operates with alnost exactly the same degree of efficiency. Results confirmed that the coagulant required for silica removal in the process water is 20-50% lower than in the effluent, especially in DAF2, where the amount of suspended solids is higher and their size is smaller. Lime softening. The higher the temperature of operation, the more efficient was the removal of silica and the necessary retention time was 15 minutes at 95°C. The facts illustrated by Table III further indicate very definitely the need for control of the alkalinity of the treated water, as unduly high alkalinity results in retaining a certain proportion of the silica in solution. C., and so is eminently well adapted for use concurrently with the lime-soda water Analysis of original sample: 136 softening process; that the magnesia process is Hardness as CaCO3--- - ....-'- 0 best carried out with the addition of sodium hyp alkalinity as aCOs--- -----------24 droxide or ts equivalent; .and that fairly close Salnity as CaCO3 ----------- 21 25 approximation of the results thus obtained are Silica as Si02 ----------------- ...similarly achieved by thie use of the slightly less economical magnesium corbonate. EFFICIENCY OF VARIOUS FORMS OF MAGNESIUM OXIDE By comparing magnesium oxide from various difference in the physical as well as the chemical characteristics of the magnesia and magnesite, a s shown by the accompanying Table V: TABLE V Turbidity Lbs./cu. As Is typical of adsorpion reactions, a greater Quantity of magnesium xide per unit of initial silica concentration is reuired where the initial silica concentration is w than is necessary where the initial silica conentration is relatively high. sSources E, F and G refer to three different sample of commercial magnesite obtained through the culcininl of mined magnesite. Also, when combining the hot lime-so4a. twh d0. Hot process softening can also provide very good silica reduction. Mere softening of the water by means of the lime-soda process at 950 C. effected the usual characteristic re- 70 duction in silica to 19 P. P. M., and the hardness to 38 P. P. M. during a retention time of 15 minutes. Streated water. water. is s 1 liter samples of water with a silica concen- l ng tration of 42 P. P. M., as SiO2 porl Temperature 95° C. 5 dus 15 minutes retention and stirring time pro 40 P. P. M. sodium hydroxide added tha ess SiO re- s Percentage hig Magnesium oxide added maining n re ed ed 10 e grams solution inm P. P.M. P. P.M. ]I= o0.1 41. . Hardness as CaCO3 ---------------- 36 40 P alkalinity as CaCO3 .--------------- 0 M alkalinity as CaC03' --------------- 26 Silica as S102---------------------Conditions: 45 15 minutes retention and stirring time 45 0.1 gram magnesium oxide added 40 P. P. M. sodium hydroxide added 1 liter samples of water -1P alkalinity is the titratable alkalinity to the phenol- 50 phthalell colorless end point (pH 8.3). Additives are used to control fouling by elevating the melting point of the deposits, by physically diluting deposits, or by providing a shear plane to assist in removal by soot blowing. Magnesium oxide is the preferred chemical because it does not increase the dissolved solids concentration of the water. MgOs were utilized to remove sulfur compounds from municipal gas. Quaternary ammonium theophylline-based ionic liquids and imidazolium-based ionic liquids, magnesium oxide and silica nanoparticles were used in order to investigate the interaction with Gram negative Escherichia coli and Gram positive Bacillus cereus.The changes of bacterial sensitivity to both nanoparticles (NPs) and ionic liquids (ILs) were examined. The low hardness of deinking paper mill ⦠The removal of silica by this process Is further akln to typical adsorption reactions in that the euantity of magnesium oxide that must be emloyed is not In a constant ratio to the amount of iica nitially present. Magnesium is removed from an aluminum alloy containing magnesium by reacting the alloy with silica to form silicon metal which dissolves in the aluminum alloy and magnesium oxide. NYACOL offers magnesium oxide and magnesium hydroxide (MgOH2) in two different dispersions. Helps prevent scale formation in boilers, heat exchangers, and piping. S Test 4-Using magnesium sulfate. MgOs were synthesized by polyol-meditation thermolysis, hydrothermal, and aerogel methods. By adding 0.1 gram magnesium oxide and without the aid of sodium hydroxide, the-silicd was sharply reduced to but 1.0 P. P, M., and the 78 xrently tends to decrease the hardness of the ter and also its alkalinity, with the further deable result of a decrease in the solids content. The residual silica even after the most diligent efforts to date, still forms a degree of impervious scale such as is extremely costly in boiler maintenance Among such efforts are those which comprise the use of salts of cadmium manganese or zinc combined with an alkali; ferrous, ferric and zinc hydroxides; and similar reagents. P.P.M. Silica is generally present in water in the form of silicilic acid polymer. s ste form, as for instance from mgn ri The net results o the research work, repreAor oagneslum sulphate. Since silica becomes part of the magnesium precipitant, some means of adding already precipitated magnesium (magnesium oxide) or of precipitating magnesium in situ is used. per cu. Conditions as in test 1. from the initial 70 p. p. M. to 72 p. P. M. Tests 4 and 5 were based upon the use of 800 P. P. M. of magnesium sulphate with 426 P. P. M. and 200 P. P. M. of sodium hydroxide, but with- 2 out any magnesium oxide. Soil Remediation. The formed magnesium oxide on the surface was carefully dissolved in 17% aqueous hydrochloric acid. Silica scaling is one of the main bottlenecks in the reuse of papermaking effluents by reverse osmosis. P. heavy magnesium oxide.---------- 33.0 206 3 Calcined magnesite (source E) .------- 45.5 3 3 Calcined magnesite (source F)-.------ 46.00 31 i Calcined magnesite (source G)------- 51. Whereas a ratio of PProximately 24 parts or less of magnesium ide perppart of silica will effect efficient silica mov. and also for extraction and removal ⦠75 In each of tests 1, 2, and 3, 300 P. P. M. magneslum oxide and 30 P. p. M. sodium hydroxide were used together, test 1 being with U. S. P. light magnesium oxide, while tests 2 and 3 were made by uing commercial magnesia from sources A and B, respectively. HoweVer, although as 5 3. There is no such delay of one-half hour in the formation of magnesium hydroxide, when the magnesium oxide is added to the water in the presence of an alkali, since the magnesium hydroxide forms im- 2 mediately. and 100 P. P. M., and the P Thus, magnesium carbonate can be used in all alkalinity being between 15% and 85% of the M of the applications in which magnesium oxide Is alkalinity and then separating the precipitate of advantage in conjunction with the hot-process from the water. Threshold limit for RO recovery and required silica removal were firstly determined by a removalâsaturationârecovery curve. Test 5-Using magnesium sulfate. The higher the temperature of operation, the more efficient was the removal of silica and the necessary retention time was 15 minutes at 95°C. Influence of suspended solids on silica removal by coagulation with aluminum salts. In this Article, we demonstrated the synthesis of mesoporous MgO hollow spheres (MgO-HS) and their application as high performance arsenite (As(III)) adsorbent. Magnesium oxide can make it harder for your body to absorb other medicines you take by mouth. Comparative tests show MgO to be superior to silica sand and garnet sand for the filtration of several different particulates. 210-23) devised, but heretofore- with only partial commercial success, due to the introduction of high dissolved solids in the treated water and the excessive quantities of treating materials reSquired. ICH.ANISIM OF RElACTION Lons by means of magnesium oxide is not a straight stoichiometric reaction, and this Is no doubt one of the principal reasons why the present process has not been earlier discovered. The samples were dried at 37 °C in air. M. to 110 P. P. M. In test 2. the removal of silica was from the initial 56 p. . Part I, Silicate-Free Peroxide Bleaching of Mechanical Pulps: Efficiency of Polymeric Stabilizers, Silica removal in industrial effluents with high silica content and low hardness, Silica removal from newsprint mill effluents with aluminum salts, Recent Developments in Controlling Silica and Magnesium Silicate Foulants in Industrial Water Systems, e-EROS Encyclopedia of Reagents for Organic Synthesis, Chemistry of silica scale mitigation for RO desalination with particular reference to remote operations, pH and Particle Structure Effects on Silica Removal by Coagulation, Application of nanocellulose in the paper industry, Anatase to Rutile Transition in Titanium Dioxide Photocatalytic Nanomaterial. lime-soda water softening. To increase silica removal, the slurries of sparingly soluble compounds were pre-acidified with concentrated sulphuric acid and tested at the same conditions. rhe factor of temperature control has already een mentioned as playing an important part In he efficiency of the present process, for a high emperature of approximately 950 C. In arld,. .EMOVAL OF SILICA AS THE RESULT OF VARYING PROPORTIONS OF MAGNESIUM OXIDE In order to illustrate the results obtained by Le use of various proportions of magnesium ide With a fixed quantity of sodium hydroxide treating water at approximately 950 C., refnce is had to the accompanying Table I: TABLE I Conditions: TAL I . 5H2O) were studied in this paper at three pHs (10.5, 11.0 and 11.5) and five dosages (250-1500 mg/L) at ambient temperature (â¼20 °C). Magnesium oxide free mesoporous silica materials have low density mesoporous silica spheres showed no XRD peaks due to complete etching of MgO core. Magnesium oxide... Convening silica into fluosilic acid. The relative values of various forms of magesium oxide for silica removal is also generally ndicated by the degree of turbidity, while this haracteristic also offers a means for comparing nagnesia obtained from similar sources. For ex%mple, the measurement of turbidity, as indicated n Table V, enables one to determine that form of nagnesia best suited for this work from similar as well as from different means of manufacture. P. P.. As the temperature is increased, while all other factors re- 7 main the same, it will be seen that at 950 C., the silica was reduced to a mere 1 P. P. M. It is also interesting to note that with an increase in temperature, other factors being equal, the hardness of the water as calcium carbonate is de- 7. ased from 88 to 28 P. P. M., while the alkalinity milarly reduced, both of which factors relatto hardness and alkalinity are of prime imtance in the conditioning of water for intrial purposes. The aerogel method had the highest surface area and sorption capacity. A brackish water source containing high magnesium concentration (333 mg/L as CaCO 3) for reverse osmosis (RO) was studied for silica scaling. Magnesium oxide being prepared by the dehydration of magnesium hydroxide at 350°C showed the greatest silica removal efficiency. Test 6 was run in order to show the comparison Sof using ferric sulphate (460 P. p. M.) with sodium hydroxide (300 P. P. M.) in lieu of either magnesium oxide or magnesium sulphate. It should also be understood t, when mention is hereinafter made to 95* C., -h expression is intended to represent the ene temperature range at which the process opdtes adjacent to the boiling point and as low as proximately 75* C. Additional tests were made with temperatures 23* C., but at such low temperature, it was und impossible to obtain results in any way apoximatng those obtained with the higher temratures noted in Table II, even when increasg the magnesium oxide to 0.3 gram and the irring and retention time to as much as 180 Inutes (3 hours), as compared with the 15 mmntes retention and stirring time used in each of ie comparative tests shown in Table IL In ct, with a temperature as low as 230 C., and 15 inutes retention and stirring time, the silica ontent is reduced from 22 P. P. M only to 19 . 32 92 8 3 2. .P.M. s anY cheaP magnesium sa.iG Pt . "" - 1. -----------sa sureB)----- 22: ~ O U. . It should be added that by increasing the sodium hydroxide to the neighbor0 hood of 40 P. P. M., and the magnesium oxide to approximately 0.3 gram, this process also serves in lieu of the lime-soda process, while simultaneously operating at high efficiency in the removal of silica. posit In boilers operating at the high tempera. s TABLE I 2 Analysis of original sample: .P.M. In the last two columns of Table IV 0 a 50% increase in magnesium oxide to 0.15 gram, both with 15 minutes and 60 minutes retention times, the silica removal was further increased to a net result of something less than 1.0 P. p. M. The effect of higher alkalinities could have 5 been attained by using either lime or soda ash in the tests represented by Table IV, but sodium hydroxide was employed for convenience in conducting the tests, wherefore and for such purpose the lime and/or soda ash are considered substltutes for the sodium hydroxide and vice vera. The salts are generally salts of magnesium/calcium (as in lime softening process) or those of aluminium/ferrous/ferric etc. ---------- 2M 25 20 88 11 10 50 duce a total M alkalinity of the treated water ~o~~s-.......between 20 P. P. IM. Additionally, the use of Ca(OH)2 instead of NaOH as pH regulator increased the chemical oxygen demand removal from 15% to 25%. As is well known, high alkalinity in treated water is exceedingly undesirable for industrial purposes, and especially in the case of boiler feedwater, which fact further indicates the need for control In the present process of the quantity of magnesium oxide, both alone and when used with other alkalies for silica removal, In order that the most efficient results may be obtained. Pure clay substance is insoluble in dilute hydrochloric acid or nitl'icacidi. Comparative tests show MgO to be superior to silica sand and garnet sand for the filtration of several different particulates. The same tables also show that a proper chemical balance must be maintained in the treated water, as otherwise increased hardness of the treated water will almost invariably result, while on the other hand, if the alkalinity of the ;reated water is permitted to rise too high, a decrease in the efficiency of the silica removal results, In addition to an undesirable degree of ncrease In the solids content and total alkalinity. I) 12 8 I 1oI water, and sufficient sodium hydroxide to pro0. P.P.M. " Plotting the data of Table I and using the logarithm of the silica remaining in solution, as related to the logarithm of the silica removed per unit of magnesium oxide employed, a straight line Is obtained which points to the inescapable conclusion that a portion at least of this process is an adsorption reaction, since the straight line referred to comprises the general form of a Freundlich Adsorption Isotherm. generation. In test 1 the removal of silica was effected down to a residual amount represented by 2.5 P. P. M., while the hardness was increased to 96 P. P. M., and the total alkalinity increased from 70 P. . P. M., while the hardness of the water was decreased from the initial 74 P. P.P M. to 66 p. P. M., which is substantially the same as that of test 2, while the total 2 alkalinity was increased by only 2 P. P. . © 2004-2021 FreePatentsOnline.com. Hierarchical magnesium oxide (MgO) microspheres with high adsorption capacity of heavy metal ions and potent antibacterial activity were synthesized by an aerosol-assisted method. In other words, the chemical reaction involved was unpredictable, especially as It depends upon several fairly critical factors, and does not definitely follow the line of previous experience and disclosures in the existing literature and patents on industrial watertreatient. Silica Removal Processes ⢠Filtration ⢠Chemical Precipitation ... always been co-precipitation with magnesium. 'wlch consists In heating LME AND SODAiEAT[LE 'NT the water to between 650 C. and the boiling point, AGNESI cARBONATE ADDED IN SLURRY FORM and admixing therewith approximately 2.4 parts MAGISIU RBONR s5 to 7.5 parts of light weight magnesium oxide per Anays otratedwater part of initial silica expressed as S1IO2 in the am Adi/ water, and sufficient sodium hydroxide to produce as leas Hard- sic re- a total M alkalinity of the treated water between Mgb Condry I e as Hard- moval 20 P. P. MI. The method of removing dissolved silica soda ash from natural water. Arsenic contamination in natural water has posed a significant threat to global health due to its toxicity and carcinogenity. By way of further comparison, such natural waters as are intended to be sed for idustrial Purposes rarely contain more than 0.1% total solids (equlvalent to 1,000 20 P. P. M.), whereas in brine there is commonly as much as 40.0% to 50.0% or even more of suspended and dissolved solids and other impurities, and at least as much as 0.3% of silica alone (equivalent to 3,000 p. P. M. or more). These materials could be tested for extraction and removal of toxic heavy metal ions as Hg 2+ [ 47 ]. by fluxing. 0 200 SCommercial magnesia (source A)-.------ 17.7 s Commercial magnesia (source B)....----- 21.2 210 24.7 100 Technical magnesium oxide-------- 247 144 2 Comme rcial magnesia (source C) ----- 2 134 U. More specifically, the Preferred form of the process comprises the use of magnesium oxide either alone, or in combination with sodium hydroxide, or concurrently instead with the common oda-lime Process, while within certain limits nagnesium carbonate can be substituted for the nagnesium oxide underPractically the same contitions. Since silica becomes part of the magnesium precipitant, some means of adding already precipitated magnesium (magnesium oxide) or of precipitating magnesium in situ is used. Concentrated sulfuric acid decompoEle's it at 2500 to' 3000 C. with the separatiO'n of sand and silica. It can be utilized as a magnesium oxide powder or granule, or converted to a magnesium hydroxide slurry for additional uses in waste water treatment. al with Initial relatively high silica concen. This short movie shows a Fresnel lens being used to focus light from the sun on a mixture of magnesium powder and silicon (IV) oxide in a boiling tube. Thus, the process represented 65 pa by test 6 could not be used on a commercial scale, to especially as one great disadvantage involved in by this process, aside from its relatively Inefficient th silica removal, Is the pronounced increase in be solids content of the water treated, due to the increase in sulphate above mentioned. wth sodium 1 36 sented by the accompaning aes ad th forethe reciitant. The method of removing dissolved silica before stated, magnesium carbonate serves In from natural water while in the hot lime-soda general as uite a satisfactory substitute for mag- softening process, which consists in admixing nesium oxide In the removal of silica from solu- therewith approxlmately 2. parts to 7.5 parts tion, magnesium oxide in the forms shown in I ht weight magnesium oxide per part of initial tonem magnesium oxide in the forms shown in light wpre as SiO2 in the water and then tests 2 and 3 of Table VI is somewhat more ORf- 60 separatingessed cipitates from the water. Test 6--Using ferric sulfate. EFFECT OF VARYING PROPORTIONS OF SODIUM HYDROXIDE From the accompanying Table III, the results will be apparent when using various proportions of sodium hydroxide with a substantially fixed proportion of magnesium oxide, while this table also indicates the definite need for controlling the alkalinity of the water. Therefore, as illustrated in Figure 2, the magnesium oxide feed system should be designed with low retention times and low makeup water temperatures. The reaction between the alloy and the silica preferably is initiated as a suspension. There is provided a process for replacing the magnesium oxide portion of a nature magnesium silicate with sodium oxide thereby to form sodium silicate which comprises melting a natural magnesium silicate and sodium carbonate at a temperature of from 1100° to 1350° C. until a clear melt is obtained, the molar ratio of sodium oxide derived from the sodium carbonate per mole of silica ⦠Magnesium oxide can not be mixed into water with an alkali such as calcium oxide, sodium hydroxide, or sodium carbonate, without the immediate precipitation of magnesium hydroxide, and magnesium hydroxide which is formed externally to the water to be treated is, as herein noted, in- 2 efficient for thfe removal of silica.
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