Microencapsulation of zinc plating waste using silicone polymers.

This paper deals with the treatment of hazardous zinc-bearing waste using hydraulic binders and silicone polymers, with the aim to allow its safe disposal into landfill. The waste was solidified using hydraulic binders in the first step and then encapsulated using silicone polymers. Samples were characterised using x-ray fluorescence, x-ray diffraction, and scanning electron microscopy. The effectiveness of the process was evaluated by leaching tests in distilled water and in an acidic environment according to Toxicity Characteristic Leaching Procedure. The effect of porosity and pH on the release of pollutants was also studied. Zinc and chloride were identified as the most significant pollutants in the waste. Portland cement did not stabilize them efficiently. The two-step treatment with Portland cement and silicone binders decreased, in the best case, the concentration of zinc and chloride in acidic extracts from 12,400 mg/L and 38,300 mg/L to 21.9 mg/L and 74 mg/L, respectively, and the treated waste complied with regulatory requirements for hazardous waste disposal into landfills. The two-step treatment was also found as a more effective method than microencapsulation using a silicone binder alone. The factor that most affects leachability appears to be the porosity of the encapsulated waste.

Stabilization/solidification of hot dip galvanizing ash using different binders.

This study focuses on solidification of hot dip-galvanizing ash with a high content of zinc and soluble substances. The main purpose of this paper is to immobilize these pollutants into a matrix and allow a safer way for landfill disposal of that waste. Three different binders (Portland cement, fly ash and coal fluidized-bed combustion ash) were used for the waste solidification. Effectiveness of the process was evaluated using leaching test according to EN 12457-4 and by using the variance analysis and the categorical multifactorial test. In the leaching test, four parameters were observed: pH, zinc concentration in leachate, and concentration of chlorides and dissolved substances in leachate. The acquired data was then processed using statistical software to find an optimal solidifying ratio of the addition of binder, water, and waste to the mixture, with the aim to fulfil the requirement for landfill disposal set by the Council Decision 2003/33/EC. The influence on the main observed parameters (relative amount of water and a binder) on the effectiveness of the used method and their influence of measured parameters was also studied.

Disposal of waste liquor from 2,5-dichlorodisulfanilic acid production.

Three alternative procedures were worked out for disposal of waste liquor from production of 2,5-dichlorodisultanilic acid [CAS No. 88-50-6]. This liquor is a hazardous liquid waste which, if discharged into a wastewater treatment plant without any treatment, inhibits processes of biological treatment. The first alternative utilizes stabilization/solidification technology by using fluidized-bed combustion ash. The second alternative consists in treating the liquor in a flow-through column packed with active carbon black as an adsorbent and discharging of the treated liquor, which already displays an acceptable chemical oxygen demand level after removal of organic pollutants by adsorption, into a wastewater treatment plant. The third alternative comprises of passing the waste liquor through the column with active carbon black and stabilization/solidification of the treated liquor by fluidized bed combustion ash. Efficiency of the liquor disposal in cases of stabilization/solidification was evaluated by determining dissolved organic carbon content, conductivity, pH, and ecotoxicity of test specimens' leachates. From results it follows that the proposed procedures represent efficient disposal of given liquid waste.

Stabilization/solidification of waste ferrous sulphate from titanium dioxide production by fluidized bed combustion product.

A treatment procedure to allow the disposal of waste ferrous sulphate was developed. This waste contains sulphuric acid and originates from titanium dioxide production. The process is based on simultaneous neutralization and stabilization/solidification (S/S) of the waste by means of fluidized bed combustion product (FBC-P). The prepared stabilized waste specimens have a solid matrix and their batch leachates display practically neutral pH and also satisfactory conductivity values. The leachate composition is notable in its absence of toxic metals and even iron.

Characterization of products from fluidized-bed combustion of coal.

The technology of fluidized-bed combustion (FBC) of coal generates byproducts that have a series of unique characteristics and potential uses in technological practice. In this study, the products of fluidized-bed combustion (FBC-P) of coal derived from Moravian heat stations, a.s. Zlin, Cinergy Global Resources, Czech Republic, were characterized. Particular attention was paid to determining the chemical composition of FBC-P, the content of polycyclic aromatic hydrocarbons (PAHs) and toxic metals in the water leachates of these FBC-P, the content of unburned carbon, the capability of FBC-P to solidify with water and form a solid matrix, and the method for discovering optimum mixing water content for FBC-P solidification. The results suggest that one of the qualitatively more important means of utilizing FBC-P could be their application during solidification/stabilization (S/S) of wastes, particularly wastewater treatment sludges.

Stabilization/solidification of salt from a waste incinerator.

A laboratory procedure was developed and verified for stabilizing salt produced by an industrial waste incinerator. This procedure is based on salt stabilization by means of an asphalt binder. Conductivity values and relevant anion contents in leachates of stabilized waste with an asphalt coating were near zero. The pH value of these leachates equaled the pH value of the water used, so that the stabilized waste salt represented inert material, posing no environmental hazard. An unusually significant reduction in the volume of processed salt occurred during stabilization. After compacting under 10.4 MPa pressure, the volume of test specimens was almost 55% smaller than the initial salt volume. In practice, this would mean more than a doubling of landfill waste capacity. Volume reduction was successfully explained by means of a mathematical model.