Enhanced fired-clay bricks incorporating cigarette butts
Creators: name: KURMUS, Hale Nur
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400505
subject: Construction materials

description: Cigarette butts (CBs) are the world's most prevalent source of waste litter. In the year 2016, 5.7 trillion cigarettes were consumed worldwide, and about 97% of the cigarette filters were composed of cellulose acetate, a modified natural polymer. In Australia, it is estimated that over 20 billion filtered cigarettes are consumed each year, of which an estimated 7 billion are littered into the environment. The littering of CBs is a growing waste management issue and requires specific planning. When CBs are littered, harmful chemicals are leached into the environment, posing major concerns for the global environment and the quality of urban and aquatic life. In cigarette smoke, it is possible to classify more than 4,000 chemical components that are generated during burning or that are distilled from tobacco, of which 69 are carcinogenic. Cigarettes are made of cellulose acetate filters, which are designed to fully or partially retain particulate smoke components. Cellulose acetate filters have poor biodegradability and can take up to 18 months to decompose under normal environmental conditions, hence, posing a serious dilemma in terms of toxic waste and litter disposal. Based on several years of research, Mohajerani et al. (2016) proposed that the CB conundrum can potentially be eliminated by incorporating 1% CBs into 2.5% of the world's total fired clay brick (FCB) production. This research is a continuation and extensive expansion of the parent research on recycling CBs in FCBs. The initial stage of the research involved a comprehensive laboratory investigation to develop techniques to recycle CB waste in FCBs without compromising the physical and mechanical properties. FCB samples were prepared incorporating 0%, 0.5%, 1%, 1.5%, and 2% CBs and were tested for shrinkage, water absorption, initial rate of absorption, density, compressive strength, and efflorescence. The results from this investigation met the Australian Standards for masonry building blocks. The second part of the research investigated the thermal conductivity and energy savings of FCBs incorporating CBs, whereby the results from the calculation and measurement method were compared. For the energy savings study, a novel method was developed to monitor the energy consumption of the furnace during the firing process of the FCB samples incorporating CBs. An increase in CB content positively resulted in a decrease in density and thermal conductivity and an increase in energy savings. X-ray micro-Computed Tomography (micro-CT) imaging was utilized to characterize the quantity, distribution, size, and shape of the micro- and macro-scale pores generated from the combustion of the CBs during the firing process. The 3D models demonstrated a homogenous distribution of pores within the brick structure. The third part of the investigation involved a comprehensive leachate analysis of heavy metals for used, unused, and shredded used CBs, paraffin wax and bitumen encapsulated CBs, and unfired and fired clay bricks incorporating CBs. The leachate analysis was conducted according to the Australian Bottle Leaching Procedure (ABLP) for pH values 2.9, 5.0, and 9.2 using the Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The leaching behavior of fired bricks incorporating CBs was considerably lower than that for the unfired bricks due to the immobilization of heavy metals during the firing process. Moreover, it was found the bitumen and wax encapsulation process successfully trapped the heavy metals present in the CBs. The leachate results for all samples were found to be below the regulatory limits set by the EPA Victoria solid industrial waste guidelines. To investigate the potential residual remaining in FCBs incorporating CBs a comprehensive polycyclic aromatic hydrocarbon (PAH) extraction analysis was conducted in the fourth part of the investigation using the Soxhlet extractor and rotary evaporator. The samples were analysed using gas chromatography-mass spectrometry (GC-MS). The PAH concentrations for all five FCB-CB mixes were well below the EPA Victoria solid waste hazard categorization threshold for industrial waste. Moreover, the samples were studied for their carbon content using the carbon, hydrogen, nitrogen, and sulfur (CHNS) analyzer and thermogravimetric analysis (TGA). The results confirm an almost 100% combustion process of CBs during the firing process. The following part of the research involved the implementation of recycling CBs in bricks on an industrial scale. A bacteriological study was conducted, which involved the investigation of the presence of ten common bacteria in two pilot studies, various sterilisation methods for CBs were examined, and three processing methods were suggested for the implementation of recycling CBs in FCBs on an industrial scale. Contact of naphthalene balls with CBs had a significant disinfecting effect on Bacillus spp. The final part of the research involved investigating the issues relative to the strong odor of CBs and the potential release of volatile organic compounds (VOCs) during the storage and manufacturing process of CBs in FCBs. The aim was to determine techniques to detect and analyze the emission of VOCs generated from CBs, along with investigating methods to minimize or eradicate the odors generated from CBs. Charcoal sorbent tubes were used to collect the gas components, and gas chromatography-mass spectrometry (GC-MS) was used to identify and quantify the VOCs generated. Ultraviolet-C (UVC) light was implemented to determine its effect on odor reduction and mitigation. The results confirm the pollutant gas production in UVC light treated CB samples is significantly less than that of untreated CB samples. This research has discussed the world CB pollution issue, potential solutions, and the scope of expansion and further development.