The content of heavy metal ions in ash from waste incinerated in domestic furnaces

The article presents the results of preliminary tests obtained from the analysis of ash coming from the combustion of various types of waste in household furnaces. The aim of this work was to examine the infl uence of various types of waste burned in household furnaces on the elemental composition of the generated ash. As part of the research, analyses of ash generated from the incineration of mixed waste, plastics, wood, textiles, rubber waste and paper were made. The content of selected metal ions: Mn, Cu, Mo, Zn, Cd, Tl, Cr, Co, Ni, As, Sn, Sb, Pb, V was determined in the tested samples, according to PN-EN ISO 17294-2: 2016-11 standard. The highest concentrations of zinc were found in the large-sized waste, rubber and textile ash samples and highest concentrations of copper were found in the plastic and paper ash samples. The highest concentrations for elements such as copper, lead, cobalt and chromium were recorded for samples of rubber and large-sized waste containing e.g. varnished furniture boards. The obtained results showed that depending on the waste incinerated, the content of selected metals was signifi cantly diff erent, and the highest concentrations were noted for samples of large-sized waste, waste from segregated plastics and waste from rubbers. The content of heavy metal ions in ash from waste incinerated in domestic furnaces 69 2013, item 21) (Waste Management Act 2012). According to the provisions of art. 155. “thermal waste treatment is carried out only in waste incineration plants or waste co-incineration plants (.)”, which explicitly prohibits the incineration of waste in uncontrolled conditions, e.g. in household furnaces (Sobolewski A. at al. 2019, Waste Management Act 2012, Zając A. 2016). In Poland, storage of ash in landfi lls is still the basic form of managing them. However, ash from domestic furnaces is often dumped into fi elds and gardens, due to the belief in their benefi cial fertilizing properties. This is the case with the combustion of pure biomass, while in the case of ash from conventional fuels or mainly from waste, large amounts of toxic elements get into the soil along with the ash, causing its permanent pollution (Kajda-Szcześniak M. 2014). All these aspects have recently led to an increase in the interest of authorities controlling the emission of pollutants over the possibility of identifying incineration in waste furnaces basing on the chemical composition of furnace waste (ash). Material and methods The research material consisted of ash coming from the incineration of waste such as plastics, textiles, rubber, paper and large-sized waste. From the collected waste, ash was prepared in laboratory conditions by burning each of the waste samples at the temperature of 550oC ± 25oC in such a way as to obtain samples of ash from total combustion and from combustion with limited oxygen access. The analytical samples prepared in this way were then mineralized by mixture of nitric acid and hydrogen peroxide in an Anton Paar microwave oven. Microwave mineralization was carried out at programmed boundary conditions: maximum temperature measured with IR sensor – 210oC, maximum internal temperature – 230oC, maximum microwave power 650 W, maximum pressure 50 bar, maximum pressure increase 0.3 bar/s. After mineralization, the samples were subjected to multi-elemental analysis by ICP-MS technique, according to PN-EN ISO 17294-2: 2016-11 standard. The analysis of the content of such elements as: Mn, Cu, Mo, Zn, Cd, Tl, Cr, Co, Ni, As, Sn, Sb, Pb, V was conducted in the samples. Results and discussion The test results of metals content in ash samples from waste are presented in Table 1. The content of individual elements in various types of ash from waste was very diverse. The highest concentrations were recorded for metal ions such as zinc in samples of waste from rubber, plastics and large-sized waste, in which the content reached even 24738 mg/kg d.m. in rubber waste (Table 1). High concentrations were also noted for copper, whose content in one of the ash sample from plastic waste was 23203 mg/kg d.m. Another element characterized by a high concentration in the tested samples is lead, whose concentration in ash samples from waste plastics was 10883 mg/kg d.m. High Large-sized waste Plastic waste Rubber waste Textiles waste Paper waste Fig. 1. Ash from waste