Solidification/stabilization of ash from medical waste incineration into geopolymers.

In the present work, bottom and fly ash, generated from incinerated medical waste, was used as a raw material for the production of geopolymers. The stabilization (S/S) process studied in this paper has been evaluated by means of the leaching and mechanical properties of the S/S solids obtained. Hospital waste ash, sodium hydroxide, sodium silicate solution and metakaolin were mixed. Geopolymers were cured at 50°C for 24h. After a certain aging time of 7 and 28 days, the strength of the geopolymer specimens, the leachability of heavy metals and the mineralogical phase of the produced geopolymers were studied. The effects of the additions of fly ash and calcium compounds were also investigated. The results showed that hospital waste ash can be utilized as source material for the production of geopolymers. The addition of fly ash and calcium compounds considerably improves the strength of the geopolymer specimens (2-8 MPa). Finally, the solidified matrices indicated that geopolymerization process is able to reduce the amount of the heavy metals found in the leachate of the hospital waste ash.

Adsorption of Cu(II) ions from aqueous solutions on biochars prepared from agricultural by-products.

In this study, the adsorption of Cu(II) from aqueous solutions by agricultural by-products, such as rice husks, olive pomace and orange waste, as well as compost, was evaluated. The aim was to obtain sorbent materials (biochars) through hydrothermal treatment (300 °C) and pyrolysis (300 °C and 600 °C). The effect of adsorbent dose, pH, contact time and initial Cu(II) concentration in batch-mode experiments was investigated. The optimum Cu(II) adsorption conditions was found to occur at 5-12 g/L adsorbent dose, initial pH 5-6, and reaction time 2-4 h. Furthermore, the adsorption kinetics were best described by the pseudo-second order model for all the tested materials, while the adsorption equilibrium best fitted by the linear and Freundlich isotherms. Comparing rice husks and olive pomace, the higher adsorption capacity resulted after pyrolysis at 300 °C. With respect to the orange waste and compost, the highest adsorption capacity was observed using biochars obtained after hydrothermal treatment and pyrolysis at 300 °C.

Solidification/stabilization of fly and bottom ash from medical waste incineration facility.

In the present work, the stabilization/solidification of fly and bottom ash generated from incinerated hospital waste was studied. The objectives of the solidification/stabilization treatment were therefore to reduce the leachability of the heavy metals present in these materials so as to permit their disposal in a sanitary landfill requiring only a lower degree of environmental protection. Another objective of the applied treatment was to increase the mechanical characteristics of the bottom ash using different amounts of Ordinary Portland Cement (OPC) as a binder. The solidified matrix showed that the cement is able to immobilize the heavy metals found in fly and bottom ash. The TCLP leachates of the untreated fly ash contain high concentrations of Zn (13.2 mg/l) and Pb (5.21 mg/l), and lesser amounts of Cr, Fe, Ni, Cu, Cd and Ba. Cement-based solidification exhibited a compressive strength of 0.55-16.12 MPa. The strength decreased as the percentage of cement loading was reduced; the compressive strength was 2.52-12.7 MPa for 60% cement mixed with 40% fly ash and 6.62-16.12 MPa for a mixture of 60% cement and 40% bottom ash. The compressive strength reduced to 0.55-1.30 MPa when 30% cement was mixed with 70% fly ash, and to 0.90-7.95 MPa when 30% cement was mixed with 70% bottom ash, respectively.

Hydrothermal conversion of chrysotile asbestos using near supercritical conditions.

The present research investigates, develops and evaluates the transformation of chrysotile asbestos into a non-hazardous material, such as forsterite, using an economically viable and safe method. The aim of this study is to convert fibrous chrysotile asbestos into an anhydrous magnesium silicate with a non-hazardous lamellar morphology using supercritical steam. The treatment method is characterized as hydrothermal in a temperature and pressure range of 300-700 degrees C and 1.75-5.80 MPa, respectively. Small amounts of asbestos (2.5 g) were treated in each experiment. Deionised water was used as the treatment solution. The treatment duration varied from approximately 1-5 h. Additional experiments took place using solutions of distilled water and small amounts of acetic acid, with the aim of attaining optimal treatment conditions. Crystal phases of the samples were determined by X-ray diffraction (XRD). The main phases present in the treated samples were forsterite, enstatite, and chrysotile asbestos. Lizardite and periclase were also found. The morphology of the treated chrysotile asbestos fibers was identified by scanning electron microscope (SEM). The fibrous form of chrysotile asbestos was converted into non-fibrous form of forsterite. In fact, none of the fibrous-needle-like morphology, with length equal to or greater than 5 microm and diameter less than 3 microm, which was responsible for the toxicity of the original material, was visible in the solid phase. The dissolution of magnesium from chrysotile asbestos was measured using volumetric determination by titration with EDTA. Leaching of magnesium into the liquid phase was observed. Clearly, the highest concentrations of dissolved magnesium are observed after hydrothermal treatment of chrysotile asbestos using acetic acid 1% (8.4-14.6%). Lowest concentrations of dissolved magnesium are obtained after hydrothermal treatment of chrysotile asbestos without using additives. Observing the results of the hydrothermal treatment using additives, the mineralogical conversion does not depend on the presence of a small quantity of weak organic acid (<1%). The addition of acetic acid 1% during hydrothermal treatment did not involve changes in the conditions of the chrysotile asbestos' mineral conversion.

Characterization and hazard evaluation of bottom ash produced from incinerated hospital waste.

The uncontrolled disposal of bottom ash from incineration units of hazardous and infected wastes in many countries causes significant scale damage, since it contaminates the soil as well as surface and underground waters, putting both the environment and the public health at risk. In view of the above, a study of bottom ash produced at a hospital medical waste incinerator (HMWI) in Greece was conducted, in order to detect the presence of heavy metals and therefore assess its toxicity; this led to conclusions on the possible contamination of the soil as well as surface and underground waters as a result of its disposal in landfills. The study was conducted at a typical general hospital with 500-bed capacity. About 880 kg of infectious waste coming from a general hospital with all medical departments are pyrolyticly incinerated at the HMWI every day. International literature contains many references to research that characterizes bottom ash as either dangerous, not dangerous, or inert, in an effort to diagnose its proper management and disposal. For this reason, this study focuses on the characterization of bottom ash. Samples were collected from a combustion chamber, over a period of 1 year, and a series of tests were conducted, including an analysis of particle size distribution, morphology, mineralogical and chemical composition, heavy metal leaching behavior and PCDD/F.

Investigative studies for the use of an inactive asbestos mine as a disposal site for asbestos wastes.

Although, according to European legislation the use of Asbestos Containing Materials is forbidden, many buildings in Greece still contain asbestos products, which must be removed at some point in the near future. Therefore, suitable disposal sites must be found within Greece, so that the unverified disposal of asbestos waste in municipal waste Landfills is brought to an end. In the present work, an innovative approach to the disposal problem of asbestos wastes in Greece has been examined, through a risk assessment analysis of the inactive asbestos mine of Northern Greece and an evaluation of its suitability as a disposal site for asbestos wastes in the future. According to the research carried out, two areas (Site 1 and Site 2) inside the mine area are suitable for the construction of a disposal site for asbestos wastes. The geological investigations showed that in Site 1 and Site 2 ultrabasic rocks of ophiolite complex were prevalent, which have been intensely serpentinized and converted into the fibrous shape of serpentine (asbestos). Concentrations of hazardous substances such as heavy metals in the soil of Site 1 and Site 2 oscillate at low levels, with the exception of the concentrations of nickel and chrome which are high. The investigative work also included the collection of meteorological data and the monitoring of the water level of the artificial lake, which has developed inside the open mine. The main aim is to safely dispose asbestos wastes inside the mine, to minimize any pollution of the wider vicinity of the mine, as well as to engage in restoration activities.

Toxicity evaluation for the broad area of the asbestos mine of northern Greece.

The existing data regarding the quality of the environment in the asbestos mine of northern Greece (MABE) region related to the presence of asbestos are insufficient to determine the current pollution problem. In the present work, a first approach to this problem has been taken through a toxicity risk assessment. The environmental quality of an open air asbestos mine was evaluated over a long period of time by measuring and monitoring the concentration of asbestos fibres in air, soil and water. Air measurements were made to determine the concentration of asbestos fibres in the atmospheric air of the mine, the depositions and the nearby villages. The asbestos fibre concentration was also specified inside the building facilities of MABE. Analyses of soil, dust and water samples were carried out showing the presence of enormous quantities of chrysotile asbestos. The concentration of asbestos fibres in the atmospheric air was compared to older measurements that were taken at the same sampling points during the operation of the mine. The results of this work, in conjunction with individual researches that have been carried out in the past and with the evaluation of international standards of scientific and experience-based findings, provide a reliable framework with which to estimate the threat of MABE to its surrounding environment, and help to determine a basic criterion for the remediation and rehabilitation of the region. In addition, mathematical models based on human and animal studies were used to estimate the probability of a person developing cancer from breathing air containing asbestos fibres in the wider vicinity of the mine in order to define appropriate procedures for evaluating asbestos-related risk.