Purpose
This investigation presents a new valorization route of fly ash, based on the synthesis of layered double hydroxide (LDH) used as efficient and cost-effective adsorbent for the stabilization ...of contaminants in sediments.
Methods
LDH were synthesized through an acid leaching method at constant pH followed by precipitation, applied on waste paper fly ash (WPFA) and biomass fly ash (BFA), obtained from industries of the Hauts de France region. The synthesized LDH (LDH
WPFA
and LDH
BFA
) were calcinated at 450 °C, their physico-chemical and adsorption properties were then compared before and after calcination, with a commercial hydrotalcite (HT).
Results
The XRD diffractograms of synthesized LDH showed characteristic bands of hydrocalumite Ca
4
Al
2
(OH)
12
(Cl,CO
3
,OH)
2
·4H
2
O and paraalumohydrocalcite (CaAl
2
(CO
3
)(OH)
4
.6H
2
O) for LDH
WPFA
and LDH
BFA
, respectively. The FTIR spectra showed similar patterns to LDH containing interlamellar anions (CO
3
2−
and OH
−
) in the vicinity of 1360 cm
−1
and 3600 cm
−1
. The LDH morphology presented platelets and hexagonal block shapes with some octahedral forms. The batch and column adsorption results showed that more than 98% of Sb, Zn and SO
4
2−
were stabilized when the sediment matrix was amended with 5% of calcinated LDH
WPFA
, compared to untreated sediment, due to the negative charge of the surface.
Conclusion
Synthesized LDH were able to stabilize both cationic species (by adsorption and electrostatic attraction), and anionic species (by anion exchange) inside the sediment matrix.
Graphical Abstract
Several studies have shown the potential of upgrading sediments in the civil engineering field. However, the complexity of sediments represents a scientific challenge in terms of their management. ...This study presents the river sediments recovery in a thermosetting matrix. The characterization results epoxy mortars show the feasibility of incorporating dredged sediments up to 50% substitution rate of natural sand. Moreover, according to the physic, mechanical, thermal and chemical evaluations of the thermosetting matrices, it appears that the performances depend on the factors of the rate of resin and the rate of sediments used. Indeed, the difference between the performances of resin mortars containing sediments and mortars without sediments is reduced by a resin content equal to 18%. In comparison with cementitious matrix mortars, the performances of polymeric mortars are well above. Finally, the SEM observations of different formulations made it possible to explain the results observed at the macroscopic scale.
Display omitted
•The packing density model makes it possible to control the porosity.•The better properties of polymer mortars obtained when resin content is at least 18%.•The polymer mortar based on sediment present a beneficial reuse for construction.•Environmental tests show the safety of materials formulated with sediments.
High sulfate concentrations in industrial effluents as well as solid materials (excavated soils, dredged sediments, etc.) are a major hindrance for circular economy outlooks. SO42- acceptability ...standards are indeed increasingly restrictive, given the potential outcomes for public health and ecosystems. This literature review deals with the treatment pathways relying on precipitation, adsorption and microbial redox principles. Although satisfactory removal performances can be achieved with each of them, significant yield differences are displayed throughout the bibliography. The challenge here was to identify the parameters leading to this variability and to assess their impact. The precipitation pathway is based on the formation of two main minerals (ettringite and barite). It can lead to total sulfate removal but can also be limited by aqueous wastes chemistry. Stabilizer kinetics of formation and equilibrium are highly constrained by background properties such as pH, Eh, SO42- saturation state and inhibiting metal occurrences. Regarding the adsorption route, sorbents’ intrinsic features such as the qmax parameter govern removal yields. Concerning the microbial pathway, the chemical oxygen demand/SO42- ratio and the hydraulic retention time, which are classically evoked as yield variation factors, appear here to be weakly influential. The effect of these parameters seems to be overridden by the influence of electron donors, which constitute a first order factor of variability. A second order variability can be read according to the nature of these electron donors. Approaches using simple monomers (ethanol lactates, etc.) perform better than those using predominantly ligneous organic matter.
In this paper, adsorption of arsenic (V) was studied under different physico-chemical conditions onto four commercial adsorbents: hematite, goethite, magnetite and zero-valent iron (ZVI). The ...reversibility of adsorption process was also studied using chlorides and phosphates as competing ions. Results show that arsenate adsorption is related to the iron content of adsorbents, and adsorption rate increases in the following order: goethite<hematite<magnetite<ZVI. The modeling of adsorption isotherms by empirical models show that arsenate adsorption is fitted by the Langmuir model for almost all adsorbents, suggesting a monolayer adsorption of arsenic onto adsorbents. Desorption experiments show that arsenic is strongly adsorbed onto hematite and ZVI. Among adsorbents, hematite appears to be the most suitable for removing arsenate in natural medium since it is effective over large ranges of pH and arsenic concentration.
► Hematite, goethite, zero-valent iron and magnetite were used to remove As(V). ► Hematite is a suitable adsorbent over wide ranges of pH and As(V) concentrations. ► Arsenate adsorption isotherms are well fitted with the Langmuir model. ► Adsorption capacity is related to the iron content of adsorbents. ► Arsenate desorption from hematite and zero-valent iron is negligible.
The management of dredged sediments poses serious environmental and economic problems because of their geochemical properties and in particular their pollutant content. In this research, marine ...sediments from Tunisian harbors were collected to study their beneficial reuse as construction materials using an eco-friendly polymer binder. Experimental investigations include the determination of physicochemical, mineralogical, and environmental parameters of sediments from the Sidi Mansour and Sidi Youssef areas in Tunisia. Prismatic mortar samples (4 × 4 × 16 cm) were prepared at laboratory scale using normalized sand and epoxy resin. Then their composition was modified by including a sediment fraction in the substitution of sand at rates ranging from 10 to 50% in dry mass. After a 7-day curing period, mortar samples were submitted to mechanical, physicochemical, and environmental analyses. Mortar samples including sediment fractions displayed lower strength than sand mortar used as control. This result is explained by the increase of porosity values in the mortar samples when sediment samples were incorporated. A positive relationship between porosity and compressive strength values was evidenced, suggesting that the compactness of granular skeleton could play an important role in the preparation of materials. From an environmental point of view, the mortar samples containing sediment fractions showed relatively low leaching levels, which confirms their suitability for the manufacturing of construction materials.
Dredged sediments display a great potential for growing media applications; however, there are few studies about their beneficial reuse for the waste storage reclamation. This research study aims at ...checking the agronomic values and environmental impacts of three growing media based on waterways sediments (WSs) and green waste (GW) according ecolabel requirements. For this purpose, three growing media named GW0, GW25, and GW50 were prepared at field pilot scale by co-composting WS and GWs during 12 months. Samples were submitted to ecolabel analyses package. Following to the ecolabel requirements, the growing media comply with criteria like pH, electrical conductivity, trace elements and polycyclic aromatic hydrocarbon contents, chlorides, and pathogens, whereas they are not in compliance with the EU Ecolabel guidelines for propagules, organic matter, and zinc contents. Results of laboratory leaching tests performed according to NF EN 12457-2 for GW0, GW25, and GW50 have shown that sulfates, soluble fraction exceed limit for inert waste storage. Lysimeter tests at pilot scale were performed during 6 months to check the leaching potential of pollutants from growing media under real field conditions, including a European ecolabel product. Results demonstrate that Ba, Mo, Sb, Zn, Se, and Sb are higher in GW0, GW25, and GW50 than in the European ecolabel. As, Cd, Cr, Ni, and F− are more soluble in the commercial product compared to other growing media. This study allowed to demonstrate that main characteristics are fulfilling for reusing these growing media in the specific field of waste storage reclamation.
Purpose
The development of the circular economy of mineral solid wastes implies searching for new treatment methods to guaranty their chemical quality and technical properties. The aim of this study ...is to use mineral solid wastes including dredged sediments (SED), construction and demolition waste (CDW), and municipal solid waste from incinerator (MSWI) to obtain backfill road materials.
Methods
Granular mixtures were prepared using Talbot-Fuller-Thompson curves to optimize their packing density. Then, these road materials were submitted to geotechnical, mechanical, and environmental analyses to validate their conformity.
Results
The results highlighted that the partial substitution of sand by CDW and MSWI seems to be the best option to enhance the mechanical properties of road materials. The replacement of sand by ternary mixtures of SED, CDW, and MSWI allowed obtaining acceptable road materials without resorting to any treatments. Equilibrium batch leaching tests performed on road materials revealed that the behavior of Ba, Cr, Cu, Sb, and Zn is mainly related to raw material properties i.e. pH, mineralogy, and pollutant contents.
Conclusions
This study highlights the opportunity to replace natural aggregates with a wide variety of mineral solid wastes. However, it is recommended to pay attention to the modification of leaching behaviors of wastes after treatment and formulation.
Graphic Abstract
The high consumption of natural sand and the accumulation of mineral wastes in landfills such as dredged sediments make it necessary to valorize the wastes as secondary materials in the field of ...construction. This work dealt with the valorization of sediments from Sidi Mansour (SM) and Sidi Youssef (SY) Tunisian harbors in geopolymer matrices. The experimental design of mixtures (sand with sediment) at 10 to 25% (w/w) of substitutions was based on the optimum packing density. The mortars were assessed for their mechanical, physicochemical, and environmental properties. The results of compressive strength are always higher than the reference mortar with an optimum at 15% of SM and 20% of SY. In addition, the mercury intrusion porosity (MIP) and porosity accessible to water (PAW) is correlated to the compressive strength values. In addition, the environmental quality of mortars was validated. The SEM analysis of mortars confirms the enhancement of adhesion of the matrix due to structurally stable of Sodium Aluminosilicate Hydrate (N–A–S–H) gel. This study revealed that the substitution of sand by sediments can be considered as a suitable option for improving physico-chemical and mechanical properties of the mortars. Also, the geopolymer binder can be effective to stabilize pollutants in the sediments.
The combustion of biomass and waste paper sludge in a fluidized bed is ecologically profitable. However, a large amount of by-product with high hydraulic reactivity is produced and is considered as ...wastes. Most of the time the waste paper fly ash (WPFA) goes to landfills, therefore new utilization methods are necessary. In some countries, the high content of metallic and metalloids trace elements (MMTE) in WPFA, more specifically Barium (Ba) and Lead (Pb) makes its valorization difficult. In this paper, the Lightweight Aggregates (LWA) was produced from WPFA by granulating with water in high-intensity granulator. Since WPFA is rich in CaO, the addition of water promotes rapid setting and hydration compared to other types of ash. In this study, different granulation parameters were investigated, such as the rotation modes between the steel pan and the impeller, the rotation speed of the steel pan, the granulation time, in order to improve the mass percentage of the targeted LWA (2–16 mm). In order to evolve the immobilization potential of Ba and Pb, a carbonation process was performed, exposing the manufactured LWA to pure carbon dioxide (CO2) gas at laboratory scale. The physical, morphological, thermal and mechanical characterizations were performed on LWA for use in mortars, concretes or civil engineering constructions.
Results have demonstrated the influence of the rotation mode between the steel pan and the on the distribution of WPFA inside the steel pan and the change in the growth rate of the granules can be observed. Increased density and improved compressive strength with low porosity and water absorption were also found in LWA after carbonation. This was due to the occurrence of both a carbonation reaction and a hydration reaction. Furthermore, the results of thermogravimetry and SEM-EDS confirmed the formation of hydrated phases (ettringite, carboaluminates), also the formation of calcite in the pores and the external surface of the LWA. Regarding environmental aspects, the results have revealed that Ba and Pb were well immobilized in the solid matrix after carbonation.
Display omitted
•LWA was manufactured from WPA without any agglomerating agents.•The physical-chemical properties of LWA were improved after carbonation.•The resulted LWA meet the requirements of NF EN -13,055-1.•The microstructure of LWA was studied before and after carbonation.•Influence of time, mode and rotation speed on the size of the manufactured LWA.
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