Translation Series No Recovery method for mercury. by Tomoyasu Ishida, and Kazuo Aiba

Transcription

1 ^ 1ï ï',c?-i}:^%i : FISHERIES RESEARCH BOARD OF CANADA Translation Series No 2506 Recovery method for mercury by Tomoyasu Ishida, and Kazuo Aiba Original tit1e: 'Suigin no kaishu hoho From: Tokkyo Koho ( Patent Gazette), : 1-2, 1971 Trânslatedby the Translation Bureau(II) Foreign Languages Division Department of the Secretary of State of Canada ^Department of the Environment Fisheries Research Board of Canada Vancouver Laboratory Vancouver, B Ç pages typescript

2 $DEP AF2pIT OF THE SECRETARY OF STATE TRANSLATION BUREAU Eetvi FRe564, SECRÉTARIAT DETAT BUREAU DES TRADUCTIONS MULTILINGUAL SERVICES DIVISION CANADA DIVISION DÈS SERVICES MULTILINGUES TRANSLATED FROM - TRADUCTION DE Japanese INTO - EN English "AlITFOR - AUTEUR Tomoyâsu Ishida and Kazuo Aiba TITLE IN ENGLISH - TITRE ANGLAIS Recovery Method for Mercury IIILE IN FOREIGN LANGUAGE (TRANSLITERATE FOREIGN CHARACTERS) TITRE EN LANGUE etrangére (TRANSCRIRE EN CARACTàRES ROMAINS) Suigin no kaishu hoho REFERFNCE IN FOREIGN LANGUAGE (NAME OF BOOK OR PUBLICATION) IN FULL TRANSLITERATE FOREIGN CHARACTERS RÉFÉRENCE EN LANGUE ÉTRANGÉPE (NOM DU LIVRE OU PUBLICATION) AU COMPLET, TRANSCRIRE EN CARACTÉRES ROMAINS Tokkyo Koho REFERENCE IN ENGLISH - RÉFÉRENCE EN ANGLAIS Patent Gazette PUBLISHER PLACE OF PUBLICATION LIEU DE PUBLICATION ÉDITEUR Japan Patent Office Tokyo, Japan YEAR ANNÉE 1971 DATE OF PUBLICATION DATE DE PUBLICATION VOLUME ISSUE NO NUMÉRO PAGE NUMBERS IN ORIGINAL NUMÉROS DES PAGES DANS LORI GINAL NUMBER OF TYPED PAGES NOMBRE,DE PAGES DACTYLOGRAPHIÉES 6 Environment REQUESTING DEPARTMENT TRANSLATION BUREAU NO -Ltil MINISTÈRECLIENT NOTRE DOSSIER N 0 BRANCH OR DIVISION DIRECTION OU DIVISION Fisheries Service TRANSLATOR (INITIA LS) TRADUCTEUR (INITIALES) PEKSON REQUESTIN G DEMANDÉ' PAR Library ApR YOUR NUMBER _ VOTRE DOSSIER N 0 "i Atl SLA'1"10 DATE OF REQUEST DATE DE LA DEMANDE March 6, 1Q73 _ UV'1 _ 4niUffie (FtEv2tee):

3 DEPARTMENT OF THE SECRETARY OF STATE TRANSLATION BUREAU MULTIONOLIAL s,ervizes SECRÉTARIAT D'ÉTAT BUREAU DES TRADUCTIONS DIVISION DES SERVICES MULTILINGUES _ CLIENTS NO DEPARTMENT DI VISION/E3RANCH CITY NO DU CLIENT MINISTERE DI VISION/DIRECTION VILLE " Environment Fisheries Service Ottawa Ont BUREAU NO LANGUAGE TRANSLATOR (INITIALS) NO DU BUREAU LANGUE TRADUCTEUR ( INI TI ALES) Japanese 11 4 P R r J PATENT GAZETTE Patent July 25, 1971 RecoVery Method for Mercury: Patent Application: Date of Application: Inventors: Applicant: Patent Attorney: Junè 17, 1969 ItomoyasuIshida 1008 Nakai, Kokura-ku, Kita-Kyushu City - Kazuo Alba, 2-1-8, Tenen, Tobataku, Kita-Kyushu City Asahi Glass Co Ltd, 1-2, Màrunouchi 2-chome, Chiyoda-ku, - Tokyo Kisami Yamazaki Detailed Explanation of Invention: This process is concerned with recovery of mercury, in particular mercury contained in waste water 'discharged by electrochemical industries, In obtaining chlorine and caustic soda:from a solution of common salt water by use of the old method of mercury UNUDITI:D,TNSI e\tic)1\1 for infolnakm only TRADUCTION NON pelsin )nform3ii9n

4 e:lectrolysis*, a portion of mercury is dissolved into salt water and caustic soda and carried away outsiç3e the electrolytic cells,:or mercury cells Part of the solution is released into waste water discharged by electrochemical plants into rivers, thus creating various pollution problems Up to now the method generally used for recovery of mercury isto bring the waste water to a level of low acidity and add sodium suiphide The solution is then treated with N a precipitating agent iron sulphate, and mercury is collected as mercuric sulphide precipitate However, in this method of forming mercuric sulphide, it is necessary to first neutralize or bring to low acidity the waste water which is à strong alkaline solution because of its caustic soda content And to neutralize a large volume of waste water requires a large amount of acid, such as hydrochloric acid Furthermore, mercuric sulphide is normally very difficult to precipitate, so the addition of a considerable amount of precipitator, such as iron sulphate, is necessary In addition to the various reagents required, other disadvantages of this process are difficulty of operation and high costs As a result of various tests and studies for a process w'nich will eliminate thè above-mentioned drawbacks and yet insure the complete removal and recovery of mercury, it was found that in treating waste water with magnesium sulphiâe or magnesium hydrosulphide as precipitator, it was readily

5 possible to recoverj/ mercury in the form of sulphide This was achieved witnou'l first making compensation for the acidity or b^sicity of waste water and adding the precipitator directly into the alkaline solution and withôut the necessity of adding any other cohesive agent The following formula is an example of the reaction obtained from this process: 2HgC g, (SH)2 + 4:IaOH --^ '2HgS + Mg (OH)2 + 4t1aC1 As stated before, waste water containing mercury is a strong alkaline solution in the phl3 region: because of its caustic soda content In this process the precipitator agent is added directly into the strong alkaline solution to achieve precipitation of mercuric sulphide However, it was found that once the waste water alkaline content was brought to phlo level and precipitator added, the falling speed of mercuric sulphide precipitate was accelerated and consequently the processing time was reduced rurthermore, if the rate of fall of the precipitate is not a consideration, the process may be applied to neutral or low acidity solution to bring about precipitation of mercuric sulphide,but it is not satisfactory for industrial purposes It is not cleary Why in this process it is readily possible to cause the precipitation of mercuric sulphide regardless of the acidity or basicity of the waste water Howaver, it is assumed that in treating the solution with magnesium suiphide or magnesium hydrosulphide to form mercuric

6 sua_phide precipitate, the precipitation reaction is quick, and when the process is carried out in an al;raline solution, as s'nôwn in the above formula, a secondary magnesium hydroxide reaction is formed to which mercuric sulph:ïde is absorbed or combined and the precipitate appears to enlarge, thus improving the precipitation rate The magnesium sulphide or magnesium hydrosulphide for use in this process may be prepared, for example, by combining magnesium hydroxide slurry with hydrogen sulphide gas, or by some other appropriate method Also-i magnesium hydroxide and hydrogen sulphide may be added directly into watte water containing mercury Actually, if the amount of magnesium sulphide or magnesium hydrosulphide is 3-10 male greater than the theoretical proportion necessary to change the entire amount of mercury into mercuric sulphide, the result achieved is the speeding:up of the precipitation rate of mercuric sulphide and secondary precipitate magnesium hydroxide In addition2 complete precipitation of mercury into sulphide precipitate is achieved There is no specially fixed reaction temperature and the process may be carried out under normal temperature -However, by setting the temperature at C, an accelerated rate of fall of precipitate is achieved: Test No l: An electrochemical plant using me-rcury electrolysis

7 process is discharging waste water (temp 40 C, Nan concentra- -5 tion 10g/1, NaOH concentration 04g/1 1 ph=12-13, Hg 5-10ppm) at a rate of 4m3 /hr The drainage is collected in'apond and from there pumped into a treatment tank As the waste water enters the tank, 35 1 solution of hydrochloric acid is added at a rate of 30 l/hr to bring the ph to level Next, magnesium hydroxide slurry and hydrogen sulphide gas are combined to form magnesium hydrosulphide and the solution is added at a ratio of about 3-10 mole to the mercury content in the waste water The overflow from the treatment tank showed a mercury content of ' ppm Test No 2: An electrochemical plant using mercury electrolysis process is discharging waste water (temp 40 C, NaC1 concentration 10g/1 1 NaOH concentration 04g/1 1 ph= Hg 5-10ppm) at a rate of 4m3 /hr The drainage is collected in a pond and from there pumped into a treatment tank As the waste water enters the tank, 35% solution of hydrochloric acid is added at a rate of 36 l/hr to bring the ph to 6-3 level Next, magnesium hydroxide slurry and hydrogen sulphide gas are combined to form magnesium hydrosulphide and the solution is added at a ratio of 3-10 mole to the mercury content in the waste water The overflow from the - treatment tank showed u mercury content of ppm

8 Coverage of patent Application: The special feature of this mercury recovery process is the addition into an alkaline waste water containing mercury ions of magnesium sulphide or magnesium hydrosulphide and the resulting formclon of mercuric sulphide precipitate and secondary magnesium hydroxide precipitate and their joint separation from the drainage