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ABSTRACT
As a traditional method of waste treatment, municipal solid waste incineration (MSWI) has become one of the main methods of urban waste treatment. However, as a byproduct of MSWI, a large amount of MSWI bottom ash is not reused in current practice. This study innovatively posits MSWI bottom ash as an eco-friendly adsorbent rather than a pollutant, exploring its potential application as a permeable subgrade material. The results reveal that MSWI bottom ash exhibits promising properties to serve as a permeable subgrade material to achieve the permeability and improve the sustainability for subgrade. Due to the arrangement of its particles, it shows excellent performance in shear strength and permeability, which are comparable to or surpass those of sandy soils. The average pore width of 14.200 nm allows heavy metal substances to be encapsulated within the matrix, significantly reducing their leachability, thereby aligning with environmental friendliness standards. Its adsorption capacity is about 6.60 mg/g, and the adsorption capacity per volume is 3.66 times and 2.04 times that of fly ash and clay, respectively. The mechanism analysis shows that the adsorption process is monolayer heterogeneous adsorption. This paper presents a novel perspective on reusing MSWI bottom ash and provides evidence supporting its effective utilization as a permeable subgrade material, offering substantial environmental benefits through enhanced adsorption ability.
Implications: Municipal solid waste incineration (MSWI) is a common method for municipal solid waste treatment, while the MSWI bottom ash is often not reused. This paper explored the explores the feasibility of using MSWI bottom ash as a permeable road base material. The results show that the particle arrangement enables excellent shear strength and permeability, comparable to sandy soil. It meets safety requirements for the leaching of heavy metals and acts as an adsorbent for pollutants leaching from permeable pavements. Furthermore, the mechanisms underlying these behaviors of MSWI were confirmed by microstructural and mineralogical analyses. These indicate that MSWI bottom ash has great potential as a permeable road base material. This paper provides a clear understanding of the physical, mechanical and environmental properties of MSWI bottom ash, which can promote its reuse in practice.
Nomenclature
| P | = | Nitrogen pressure (kPa) |
| P0 | = | Saturated vapor pressure of nitrogen (kPa) |
| V | = | Nitrogen adsorption capacity (cm3/g) |
| Vm | = | Saturated adsorption capacity of nitrogen monolayer (cm3/g) |
| C | = | Constant related to the adsorption capacity |
| τf | = | Shear strength (kPa) |
| σ | = | Normal stress (kPa) |
| φ | = | Internal friction angle (°) |
| c | = | Cohesion force (kPa) |
| v | = | Outflow velocity (cm/s) |
| k | = | Hydraulic conductivity (cm/s) |
| i | = | Hydraulic gradient |
| Qt | = | Unit adsorption amount at a certain time (mg·g−1) |
| Qe | = | Unit adsorption amount at equilibrium (mg·g−1) |
| t | = | Reaction time (min) |
| k1 | = | Pseudo first-order kinetics rate constant (min−1) |
| k2 | = | Pseudo second-order kinetics rate constant (g·mg−1·min−1) |
| kint | = | Intraparticle diffusion relevant rate constant (mg·(g·min1/2)−1) |
| Cint | = | Intraparticle diffusion constant (mg·g−1) |
| Qm | = | Maximum adsorption capacity (mg·g−1) |
| Ce | = | Mass concentration in equilibrium (mg·L−1) |
| KL | = | Langmuir isotherm characteristic constant (L·mg−1) |
| KF | = | Freundlich isotherm characteristic constant (mg·g−1) |
| 1/n | = | Adsorption efficiency |
| γ | = | Nonuniformity coefficient |
| Ks | = | Sips isotherm characteristic constant |
| KRP | = | Redlich – Peterson isotherm constant |
| αp | = | Redlich – Peterson isotherm constant |
| β | = | Redlich – Peterson isotherm constant |
Disclosure statement
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Data availability statement
The data of this study are available from the corresponding author upon reasonable request.
Author contribution statement
Qiang TANG: Conceptualization; Angran TIAN: Data curation; Angran TIAN and Yu ZHOU: Formal analysis; Yuru CHEN and Qiang TANG: Investigation; Angran TIAN, Deming KAN and Yanling LU: Methodology, Project administration; Qiang TANG: Supervision; Angran TIAN: Visualization; Angran TIAN and Qiang TANG: Writing – original draft, Writing – review & editing.
Supplementary data
Supplemental data for this article can be accessed online at https://doi.org/10.1080/10962247.2024.2319764.
Additional information
Funding
Notes on contributors
Angran Tian
Angran Tian is a master student at Soochow University.
Yu Zhou
Yu Zhou is a master student at Soochow University.
Yuru Chen
Yuru Chen is a master student at Soochow University.
Deming Kan
Deming Kan is a master student at Soochow University.
Yanling Lu
Yanling Lu is a master student at Soochow University.
Qiang Tang
Qiang Tang is a full professor at Soochow University.