Remotox - Aqueous Calcium Polysulfide for Wastewater Treatment - Water and Wastewater - Water Treatment
Remotox for Removing Heavy Metals from Wastewater
Heavy metals, such as copper, zinc, mercury, cadmium, nickel, lead, chromium and arsenic, can be found in many wastewater sources including, printed circuit board manufacturing, electroplating & surface finishing, copper polishing, paint manufacturing, wood preservatives and stormwater runoff.
Remotox is a water-soluble calcium polysulfide liquid that consists of multiple sulfur compounds, which strongly bond to these highly soluble metals. The metal sulfides formed have a very low solubility and persist as stable solids, which allows for a more environmentally sound disposal.
Application Advantages:
- High reactivity with heavy metal ions and extremely low solubility of resulting metal sulfides over a wide pH range. See Sulfide vs. Hydroxide Precipitation.
- Ability to remove metals from chelated metal compounds by ligand exchange process.
- Removes chromates and dichromates without preliminary reduction of the chromium to its trivalent state.
- Selective metal precipitation allowing for recovery of valuable metals.
- Converts cyanide wastes into less toxic thiocyanate ions. See Application of Polysulfide for Pretreatment of Spent Cyanide Liquors.
- Dissolved calcium ions form a coagulant aid (Ca(OH)2).
- Better settling and dewatering aspects of the metal sulfides, resulting in a more compact solid sludge. See abstract on Source Reduction Technology Report in Circuit Board Manufacture.
- Remotox can be adapted to enhance any existing treatment system.
Product Features
- A strong yet relatively inexpensive metal precipitant.
- Not regulated by the US DOT as hazardous material.
- Its residues are inert and non-toxic.
- Dissolved calcium ions form a coagulant aid.
- Unlike carbamate and carbonate salts, it does not contain or release carbon disulfide.
- No need to dissolve prior to use as compared to solid material.
- It has a low salt crystallization temperature and a shelf-life of minimum one year.
- Compared to other sulfides, it provides more stability in acidic medium. It is much safer to handle. See Process for Separating Heavy Metals from Wastewater by Calcium Polysulfide.
When mixed with water, Remotox decomposes to form bisulfide, aqueous hydrogen sulfide and other sulfur compounds. Most heavy metal ions are precipitated as metal sulfides by these breakdown products. Metal sulfides are much less soluble than metal hydroxides. Metal hydroxides change solubility with changes in pH. Metal sulfides remain insoluble within a wide pH range. See Solubility of Metal Hydroxides and Sulfides as a Function of pH.
In the case of chromium, Remotox reduces hexavalent chromium to trivalent state which then precipitates as chromium hydroxide in a one-step reaction; therefore, no need for sodium bisulfite, metabisulfite, sulfur dioxide or sulfuric acid. See Overall Effectiveness of Water Treatment Process for Cr(III) and Cr(VI).
While effective treatment can be achieved over a wide pH range, best results are typically obtained within water system pH 7-10. See pH Guidelines for Treatment of Soluble Metal Streams. Ensuring adequate contact time and thorough mixing is critical to successful treatment. Dewatering the resulting precipitate can be expedited by employing an anionic flocculant.
For technical assistance, product samples or pricing information, please contact us at 1-623-328-5175 or by email at info@grauschemicals.com.
