Perbandingan Proses Penurunan Kromium Heksavalen oleh Ferus Sulfat dalam Medium Berasid dan Beralkali

Lau, Ming Ngo, and Siti Rozaimah Sheikh Abdullah, and Saleha Atan, (2004) Perbandingan Proses Penurunan Kromium Heksavalen oleh Ferus Sulfat dalam Medium Berasid dan Beralkali. Jurnal Kejuruteraan, 16 . pp. 17-26. ISSN 0128-0198

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Affiliations

Universiti Kebangsaan Malaysia.. Faculty of Engineering. Dept. of Chemical Engineering and Processes
Universiti Kebangsaan Malaysia.. Faculty of Engineering. Dept. of Chemical Engineering and Processes
Universiti Kebangsaan Malaysia.. Faculty of Engineering. Dept. of Chemical Engineering and Processes

Abstract

Reduction process followed by precipitation is the most common method used in treating wastewater containing chromium ions. In this study, hexavalent chromium reduction process was carried out in both acidic and alkaline mediums. Ferrous sulphate solution was used as a reducing agent to reduce hexavalent chromium (Cr6+) to trivalent chromium (Cr3+). The reaction in alkaline medium at pH 9.0 was achieved by adding sodium hydroxide solution (NaOH) since chromium wastewater was acidic. During the reaction, the addition of ferrous sulphate solution into reaction medium was monitored through oxidation-reduction potential (ORP) parameter. The results showed that the ORP profiles for the reduction process were different in both acidic and alkaline mediums. When the reduction process was completed in the acidic medium, the absolute ORP value was recorded as 380 mV. The absolute ORP value when the reduction process completed in the alkaline medium was in the range of 0 to –300 mV. The total precipitation in the alkaline medium was 1.6 times higher than acidic medium. For the reduction process in both acidic and alkaline mediums, the rate of reduction process was faster for the higher concentration of Cr6+ion. However, the rate of reduction process in the acidic medium was faster than the alkaline medium because the reduction of Cr6+ concentration was greater in the acidic medium.

Proses penurunan yang diikuti dengan pemendakan merupakan satu kaedah perawatan air sisa berkromium yang paling lazim digunakan. Dalam kajian ini, proses penurunan kromium heksavalen dilakukan dalam kedua-dua medium berasid dan beralkali. Larutan ferus sulfat digunakan sebagai agen penurunan bagi menurunkan kromium heksavalen $Cr^{6+}$ kepada kromium trivalen $Cr^{3+}$ . Rawatan dalam medium beralkali pada pH 9.0 perlu ditambahkan dengan larutan natrium hidroksida (NaOH) bagi meningkatkan larutan kerana air sisa berkromium adalah berasid. Ketika tindak balas berlaku, penambahan larutan ferus sulfat ke dalam medium tindak balas dikawal dengan memerhatikan potensi penurunan-pengoksidaan (ORP). Susuk ORP bagi proses penurunan yang berlaku dalam medium berasid dan beralkali mempunyai bentuk yang berbeza. Takat penghabisan ion $Cr^{6+}$ dalam medium berasid adalah sekitar 380 mV. Takat penghabisan ion $Cr^{6+}$ dalam medium beralkali pula berlaku dalam julat nilai mutlak dar 0 ke -300 mV. Jumlah enapcemar yang terbentuk dalam medium beralkali adalah 1.6 kali lebih banyak berbanding dalam medium berasid. Bagi proses penurunan dalam kedua-dua medium tindak balas, kadar penurunan adalah lebih cepat bagi kepekatan ion $Cr^{6+}$ yang lebih tinggi. Namun begitu, kadar penurunan adalah lebih cepat bagi proses penurunan yang berlaku dalam medium berasid kerana kepekatan ion $Cr^{6+}$ menurun dengan lebih cepatnya dalam medium berasid.

Item Type:

Journal

Keywords:

kromium heksavalen, penurunan kromium, ferus sulfat,potensi pengoksidaan-penurunan (ORP).

Subjects:

Q Science, Computer Science
T Technology, Engineering

ID Code:

4170