1. Introduction

Traditionally, the removal of heavy metals from wastewaters has relied on the precipitation of classic hydroxides using caustic, lime, or, in special cases, sodium carbonate. This method is based on changes in solubility values of metal hydroxides, metallic carbonates, or other alkaline salts. In Germany, recent discharge specifications for heavy metals have become more stringent, as outlined in 40. Abw.VwV. Compliance with these values poses challenges in standard hydroxide precipitation operations, especially when dealing with weak complexing agents, surfactants, or standard salts.

There are technologies available to meet the new discharge requirements:

  1. Physical-chemical “exchange” technologies: Ion exchange, ultrafiltration, electrodialysis, etc.
  2. Use of a new generation of precipitants: Forming reaction products with heavy metals of lower solubility compared to hydroxides.

Physical-chemical processes may require investments, and existing precipitation installations may lack space for expansion. However, modern precipitants, particularly those based on sulfur compounds, offer adaptability to existing installations, often in combination with traditional hydroxide precipitation.

  1. Disadvantages in the use of organic products

Organosulfide compounds exhibit significant drawbacks compared to inorganic sulfur products:

  • Applicability limited to neutral or alkaline conditions due to the formation of inefficient free acids in acidic media.
  • Heat instability of reaction products when dealing with heavy metals.
  • Difficulty in application due to strong complexing compounds, requiring complex displacement steps in alkaline pH ranges.
  • Some organic sulfides are suspected to be carcinogenic, mutagenic, and teratogenic to mammals.

The use of inorganic thio compounds in wastewater treatment was historically limited due to the risk of toxic hydrogen sulfide emissions. However, NETfloc SMF-3, based on inorganic thio sulfuric compounds, addresses these concerns.

  1. Advantages of NETfloc SMF-3

NETfloc SMF-3, a product based on sulfur, addresses the drawbacks associated with hydrogen sulfide evolvement. Its efficiency in precipitating heavy metals has been proven through scientific research, offering advantages such as:

  • Applicability in acidic and neutral pH ranges.
  • Excellent sedimentation characteristics of precipitated solids.
  • Capability to process and recycle heavy metal compounds formed.
  • Residual concentrations of dissolved heavy metals below required discharge permit values.

The in-situ interaction mechanism of bonding hydrogen sulfide makes NETfloc SMF-3 more effective than standard sulfur-based products.

  1. Application Areas

NETfloc SMF-3 is used in wastewater treatment for challenging scenarios where low discharge values are difficult to achieve or extreme low residual concentrations are required. Additionally, it finds application in new wastewater treatment technologies and various industries producing liquids containing heavy metals.

Examples include leachate from landfills, gas scrubber systems in power plants, gas scrubber systems of waste incineration plants, galvanizing industry, and automobile industry.

In addition to wastewater purification, NETfloc SMF-3 can be employed for in-situ and onsite soil treatment and general immobilization of heavy metals in sludges.

  1. Handling

NETfloc SMF-3 is typically used in a somewhat acidic pH range (pH 3.0 – 4.5). The required dosage depends on the heavy metal concentration in the wastewater. The treatment sequence includes pH adjustment, dosing of Fe(II)Cl2, dosing of NETfloc SMF-3, neutralization, and potential addition of a flocculant for separation of reaction products.

  1. Technical Data
  • Appearance: Orange-red, clear alkaline liquid
  • pH: 12.0 – 13.5
  • Density, 20 °C: 1.150-1.250 g/cm³
  • Solubility in water: Unlimited
  • Boiling point: > 100 °C
  • Crystallization point: < -5 °C
  • Viscosity: < 50 mPaS (20 °C)
  • Shelf life at 6 °C – 50 °C: Minimum 1 year
  1. Delivery

NETfloc SMF-3 is delivered in PE 30l/220l containers or 1,000l IBC containers. Bulk deliveries can also be discussed.

  1. Comments

If mixed with concentrated mineral or organic acids, the product may release harmful gases, particularly hydrogen sulfide. Consultation for storage, handling, and detailed information is available, and the information in the document is based on current knowledge and not a guarantee of properties and shelf life.

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