Waste Seashells Research Articles

Effect of synthetic C-S-H seeds on hydration process, mechanical properties and microstructure of seashell powder calcined sludge cement

Seashell powder calcined sludge cement (SCSC) is a new type of green low-carbon ternary cement prepared by using waste sludge and waste seashells. It reduces carbon emissions in the cement production industry and solves environmental problems such as serious soil-water-air pollution caused by long-term stockpiling of waste sludge and waste seashells, which are difficult to be utilized in a resourceful manner. However, the reduced clinker content results in lower early strength of SCSC, which limits the application of SCSC in applications requiring high early strength such as precast concrete specimens. In this paper, the effects of different dosage of C-S-H seeds on the hydration process, mechanical properties and microstructure of SCSC slurries were investigated. The results showed that C-S-H seeds significantly increased the 12-hour compressive strength of SCSC, and the 2 % addition of C-S-H seeds increased its compressive strength by 271 %, but had less effect on its later strength. The proportion of large pores in the sample with a 1 % addition of C-S-H seeds decreased by 1 %. At 12 hours, 2 % addition of C-S-H seeds increased its total hydration exotherm by 141 %. The addition of C-S-H seeds decreased the fluidity of the slurry but did not change the flow pattern of the slurry. The relationship between the rheological parameters of the slurry and the addition of C-S-H seeds was well fitted with a primary function, and the rheological equations of SCSC slurries with different additions of C-S-H seeds were obtained. The results of this paper can further broaden the application scenarios of SCSC and lay the foundation for the large-scale application of SCSC.

Recycling of waste glass powder: Effects on microstructure, mechanical properties and sustainability of seashell powder calcined sludge cement

The massive accumulation of waste seashells, waste sludge and waste glass not only occupies a large amount of land resources, leading to a shortage of land resources, but also causes serious soil-water-air composite pollution over a long period of time with the role of the surrounding environment, which poses a serious hazard to the ecological environment and public health. In this study, the effect patterns of waste glass powder (WGP) on the workability, mechanical properties, microstructure and carbon emission of seashell powder calcined sludge cement (SCSC) slurries prepared using waste sludge and waste seashells as supplementary cementitious materials in place of part of the cement clinker were investigated. The hydration process and microstructure of the materials were characterized by heat of hydration tests, thermogravimetry (TG-DTG), infrared Fourier transform (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the addition of WGP improved the fluidity of SCSC slurries and reduced the shear stress of SCSC slurries without changing the flow pattern of SCSC slurries, and all the slurries conformed to the power law model. The compressive strength of SCSC slurries increased by 25.26 % with 5 % WGP addition. The CO2 emissions per cubic meter of SCSC slurries were reduced by 4.43 %, 8.81 %, 13.5 % and 18.23 % for WGP additions of 5 %, 10 %, 15 % and 20 %, respectively. These results can provide a new way for the efficient resource utilization of waste seashells, waste sludge and waste glass, and reduce the CO2 emission during the cement production process, promoting the clean production of cement.

Preparation and Characterization of Hydroxyapatite Using Precursor Extracted from Cockle Shell Waste

Hydroxyapatite (HAP) is a widely used biomaterial due to its excellent bioactivity, biocompatibility, and structural similarity to the mineral component of human bone and teeth. However, the synthesis of HAP typically relies on expensive and non-renewable precursors, which can limit its widespread applications. This study investigates the extraction and purification of HAP from cockle shells, which are a readily available and renewable source of calcium carbonate. The extraction and purification of hydroxyapatite (HAP) from cockle shells, which are rich in calcium carbonate, is a promising method for producing HAP for biomedical applications due to its bioactivity and biocompatibility. This study investigates the use of a calcination process and wet slurry precipitation technique to produce HAP from seashells, focusing on the effect of reaction time of phosphate source (KH2PO4) and calcium oxide (CaO) on HAP production. EDX reported Ca/P ratio of 1.61 for HAP synthesized by chemical precipitation for 2 hours of reaction. Meanwhile, the XRD results indicate that a 4-hour reaction time produces more crystalline HAP than shorter reaction times, highlighting the importance of reaction time in HAP synthesis. This research demonstrates the potential of utilizing seashell waste as a valuable natural resource for applications in healthcare and waste management.

Application study of seashell powder calcined sludge cement: Effects of different superplasticizer on working properties, mechanical properties and microstructure of materials

Seashell powder calcined sludge cement (SCSC) is a low carbon ternary cement prepared from waste seashells and waste sludge. However, the addition of seashell powder and calcined sludge reduces the working performance of the material and restricts the engineering application of SCSC. To enhance the adoption of SCSC in construction projects, this investigation evaluates the influence of three distinct superplasticizers—Polycarboxylate Ether (PCE), Sulfonated Naphthalene Formaldehyde (SNF), and Sulfonated Melamine Formaldehyde (SMF)—on the workability, mechanical strength, and microstructural properties of SCSC. The effects of superplasticizers on SCSC slurries were analyzed by mechanical property tests and macro-micro property characterization means such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared (FTIR), hydration thermal analysis and nuclear magnetic resonance (NMR). The results showed that the fluidity of SCSC slurries was increased by 73.3 %, 32 %, and 23.5 %, the initial setting time was extended by 29.6 %, 21.3 %, and 16.6 %, and the compressive strength was increased by 22.7 %, 19.6 %, and 5.7 % for the additions of PCE, SNF, and SMF at an amount of 0.25 %, respectively. The addition of superplasticizers prolonged the hydration induction period of SCSC, optimized the pore size distribution of the material, and reduced the structural porosity. The study shows that PCE has the best suitability for SCSC slurries, and should be preferred in the practical application of SCSC slurries. The results of the study can provide a reference for the application of SCSC slurries in engineering.

Using waste to improve the weak: Recycled seashell as an ideal way to regulate the interfacial transition zone in biochar-cement composites

The strategy of partially substituting cement with carbon-negative biochar to fabricate biochar-cement composites can represent a promising approach to reducing the carbon emissions of the construction industry. However, the detrimental impact on strength development from excessive biochar incorporation remains a significant challenge. To address this issue, this study pioneers a strategy to modify wood waste-derived biochar using seashell waste for enhancing its binding with the cement matrix. Employing a mechanochemical process, the shell-modified biochar was synthesized using oyster shell (OS) and wood waste (WW). The compressive strength of cement composites incorporating 5 wt% modified biochar improved by 3.9–17% compared to the referenced biochar. Even with high biochar incorporation (30 wt%), the compressive strength increased by 58.2% upon modifying the biochar at the OS/WW ratio of 1:9 (10SBC). The modified biochar refined the pore structures, accelerated the hydration kinetics, improved the degree of hydration, and fostered the development of the C-S-H gel network with a longer silicate chain and a higher polymerization degree. Furthermore, the strength enhancement of the biochar-cement composites was attributed to the improved micro-mechanical properties at the interfacial transition zone (ITZ), which increased the volume fraction of high-density C-S-H by 64.4–112% and decreased the low-density C-S-H fraction by 41.8–52.6%. Notably, 10SBC demonstrated a superior improvement due to its cohesive bond with the C-S-H gel and the concurrent densification of C-S-H in the ITZ, which was facilitated by the growth of Ca-/Al-rich hydration products. Overall, this study synergistically upcycled wood and seashell waste into value-added cement additives, thereby achieving strength enhancement of the cement composites.

PENGARUH FRAKSI VOLUME DAN PEMBEBANAN TERHADAP SIFAT FISIK DAN MEKANIK KOMPOSIT BERPENGUAT SERBUK CANGKANG KERANG LOKAN

The increasing consumption of local clam shells which contain high nutritional value in society has resulted in an increase in waste sea shells in areas around the coast of Bengkulu Province. The high calcium content in lokan clam shells attracts researchers to study the physical and mechanical properties of epoxy resin composites reinforced lokan clam shell powder. This research aims to investigate the effect of variations in the volume fraction of lokan clam shell powder and the mold loading on the physical and mechanical properties of composites reinforced lokan clam shell powder. The process of manufacturing shell powder is carried out by heating at a temperature of 900oC for 6 hours. Variations in the volume fraction of lokan clam shell powder consist of 30, 50, 70%. Meanwhile, the mold loading was varied by 0, 500 N, and 1 kN. The manufacturing process uses hand lay-up techniques. Physical and mechanical tests on composites include water absorption tests, density, tensile tests and impact tests. The results of the research show that the powder volume fraction and mold loading influence the physical and mechanical properties of composites reinforced lokan clam shell powder. The best physical properties of composite were obtained at a powder volume fraction of 70% and a mold loading of 1 kN, namely with a density of 1.43 g/cm3. The best mechanical properties of composite were obtained at a volume fraction of 30% and a mold loading of 1 kN, namely with a tensile strength of 33.2 MPa and an impact toughness of 366.8 kJ/m2.

3D printing of cementitious composites with seashell particles: Mechanical and microstructural analysis

Seashells are abundantly available as waste products from the seafood industry and from coastal areas. Accordingly, processed shells can be used to partially replace aggregates in traditional concrete. This paper investigates the effects of different proportions of seashell particles on the mechanical and microstructural properties of 3D-printed cementitious composites. The seashells were crushed and milled to be transformed into seashell particles, replacing the river sand at 15 wt% and 30 wt%. It was found that when the seashell particle content increased to 15 wt% and 30 wt%, the mechanical strengths all decreased significantly, which could be attributed to the increasing volumetric proportion of voids and the lower elastic modulus of seashell particles compared to river sand. However, when the seashell particle proportion further rose from 15 wt% to 30 wt%, the mechanical strengths did not continue decreasing substantially. Instead, the compressive and indirect tensile strengths nearly levelled off with minor fluctuations. Based on the microstructural analysis results, it was inferred that the fine seashell powders as part of the seashell particles, which were comprised of aragonite-based calcium carbonate, participated in the cement hydration process that could help with microstructure densification of the cement matrix. This positive effect brought by the fine seashell powders was thought to prevent the further weakening of mechanical properties. Overall, this study aims to understand the role of seashell particles on the mechanical performance of 3D-printed cementitious composites from the perspectives of microstructural characteristics, further promoting the utilisation of waste seashells in 3D concrete printing applications.

A simultaneous optimization of the seawater bittern and waste seashell recovery process for CO2 and SOx utilization

This study proposes a novel integration of seawater bittern and waste seashell recovery processes for CO2 and SOx utilization. Furthermore, simultaneous optimization of waste seashells and Ca(OH)2 separated from seawater bittern as an SOx absorbent was conducted to derive the blending ratio using a genetic algorithm (GA). The GA-based optimization process consists of four steps: (1) data generation using process model and data preprocessing, (2) DNN-based surrogate model development to predict the gypsum purity, CaCO3 yield, and CO2 emissions, (3) mathematical model development for TAC calculation, (4) GA-based optimization to derive the cost-optimal blending ratio and TAC. As a result, the derived cost-optimal blending ratios were scallop shells (0.03 %), cockle shells (0.03 %), clam shells (13.66 %), oyster shells (40.31 %), mussel shells (28.80 %), and Ca(OH)2 (17.18 %), reducing the TAC by up to 10.88 % compared to conventional CO2 and SOx capture processes. At the optimal blending ratio, the recycling efficiency of each seashell in the Republic of Korea was achieved from a minimum of 2.72 % to a maximum of 99.15 % annually. Therefore, this work makes a significant contribution to the chemical engineering field, providing an environmentally friendly, economical process and an efficient simultaneous optimization framework applied to the proposed model.

Valorization of waste seashells for neutralization of sunflower oil

In this study, an investigation was conducted to explore the potential of utilizing calcium oxide (CaO) derived from carbonized seashells for the purpose of acid removal. Consequently, the objective of this research is to develop an alternative bio-material to be employed in the neutralization process. The CaO produced was compared to the conventional utilization of caustic (NaOH) based on various parameters related to oil quality. It was observed that the removal rates of free fatty acid content using CaO and NaOH were 61% and 85% respectively. Furthermore, it was determined that the use of CaO did not result any adverse effects on the composition of sterols and fatty acids during the neutralization process. On the contrary, the preservation of total sterol content was superior in comparison to NaOH. The neutralization loss observed with CaO was comparable to that of NaOH. Consequently, CaO demonstrates promise as an alkaline substitute for acid removal in vegetable oils. Additionally, it is well-suited for implementation under minimal process conditions, which have become increasingly popular in recent years.

Effect of seashell powder as binder material on the performance and microstructure of low-carbon sustainable alkali-activated concrete

This paper proposes using waste seashells as raw materials to partially replace fly ash in alkali-activated concrete (AAC). Fifteen groups of alkali-activated mortar and concrete were designed, with seashell powder (SP) substitution and sodium hydroxide molar concentration as variables. The material's workability, compressive strength, hydration products and micropore structures were examined. The results showed that the 3 days compressive strength of AAC with SP enhanced significantly, exhibiting an increase of nearly 30 % compared to the fly ash control. The 28 days compressive strength showed that the optimal proportion of SP replacing fly ash was 45 %. SEM images showed that micro/nanoparticles of SP filled the pores in the concrete and provided nucleation sites. Nano CT and MIP analyses indicated that the addition of SP could refine the pore structure of concrete, reducing the total porosity by nearly 30 %. Finally, the carbon emission data for 1 m³ of concrete were analyzed using a life cycle assessment approach. The carbon emissions from AAC with 45 % SP were 173.4 kg CO2/m³, compared to the reference ordinary concrete reduction of approximately 60–70 %.

Experimental Investigations on Physical and Mechanical Properties of Hybrid Bamboo Composites

The present study aims to develop a novel hybrid composite by incorporating clamshell as a secondary reinforcing filler into a bamboo-epoxy composite. The primary objective of this hybridization is to optimize the synergistic benefits of each component, harnessing the strength of bamboo fibres, the durability of epoxy, and the cost-effective repurposing of the waste clamshell. Compression moulding was employed to develop composites with varying filler content (0- 9 wt%). The effect of filler on the physical and mechanical properties of bamboo-epoxy composites was evaluated by conducting tests as per ASTM standards. Experimental results show that the addition of clamshell filler significantly improved composites' properties, but there was a limitation to the addition. Hardness, tensile, and flexural properties were increased, whereas impact strength was reduced. Composites with 6 wt% clamshell exhibited optimum properties, enhancing tensile strength by 20.5% and flexural strength by 24.4 % compared to composites without filler. SEM analysis of fractured tensile and bending specimens revealed an enhanced fibre-matrix bonding with the inclusion of filler and supported the experimental results obtained. The outcome of this study contributes to sustainable development by using natural resources like bamboo fibre and repurposing seashell waste to create cost-effective composite material with enhanced properties.

Valorization of waste seashells as bioadsorbent for sunflower oil bleaching

AbstractIn this study, the performance of waste seashells (SS) in adsorbing color and oxidation parameters during the bleaching process of sunflower oil was evaluated and compared with that of commercial clay. Seashell activation methods included microwave treatment (900 W for 30 min), acid treatment (7 N H2SO4), and a combination of both. Interestingly, the unactivated SS demonstrated superior adsorption performance compared with the activated SS. SS, which have the ability to eliminate color pigments like chlorophyll and carotenoid, were found to be effective in this regard. However, their effectiveness in reducing the peroxide and p‐anisidine value was not as successful as that of commercial clay. Free acidity content remained constant across all treatments. SS emerged as a cost‐effective alternative adsorbent, promising in preventing environmental pollution. Their use signifies a valuable contribution to sustainability. This study sheds light on SS potential as an eco‐friendly solution in industrial processes, warranting further exploration and application.Practical applicationsBiowaste valorization is a process that involves converting organic waste materials into valuable products, energy, or resources, instead of simply disposing of them in landfills or incinerating them. This approach has gained significance owing to its potential to address environmental, economic, and social challenges. In this respect, this study presents that bioadsorbent obtained from waste SS can be utilized for bleaching of sunflower oil.

Preparation of Adsorbent from Mechanochemical Reaction-Based Waste Seashell with Sodium Oxalate and Its Application in Pb Ion Adsorption

Waste seashell (scallop shell)-based adsorbent was prepared via mechanochemical reaction with sodium oxalate using ball milling. The oxalate-modified seashell-based adsorbents (OS) were prepared by varying the molar ratio of calcium and oxalate to 0.5, 1, and 2. Sodium oxalate was used as the aqueous solution in ball milling. Lead ion adsorption was conducted with the prepared adsorbent. The adsorption behavior of lead ions was investigated in terms of adsorption kinetics and adsorption equilibrium. The time course of the amount of Pb adsorbed agreed well with Langmuir rate equation. The adsorption equilibrium relationship of OS adsorbent and Pb agreed well with the Langmuir adsorption isotherm. Increasing with the molar ratio, the saturated amount of Pb adsorbed increased slightly from 5.45 × 10–3 to 6.23 × 10–3 mol/g. Under the present experimental conditions, the maximum equilibrium adsorption was 5.93 × 10–3 mol/g, which is greater than that reported in the literature.

Fabrication of Porous Anorthite Ceramic Insulation Using Solid Wastes.

Porous anorthite (CaAl2Si2O8) ceramics, suitable for thermal insulation in buildings, were obtained using waste seashells as a source of CaO, kaolin as a source of Al2O3 and SiO2 and banana peel as a pore former. Changing the volume of banana peel as well as the processing temperature was found to be an effective approach to control the thermo-mechanical properties of the obtained anorthite ceramics. The sintering of powder compacts containing up to 30 wt% banana peel at temperatures ranging from 1100 to 1200 °C resulted in anorthite ceramics possessing up to 45% open porosity, a compressive strength between 13 and 92 MPa, a bulk density between 1.87 and 2.62 g/cm3 and thermal conductivity between 0.097 and 3.5 W/mK. It was shown that waste materials such as seashells and banana peel can be used to obtain cost-effective thermal insulation in buildings.

Properties of Cementitious Materials Utilizing Seashells as Aggregate or Cement: Prospects and Challenges.

Nowadays, the sustainable development of the construction industry has become a focus of attention. Crushing and grinding waste seashells originating from the fishery industry, such as oyster shells, cockle shells, mussel shells, and scallop shells, into different particle sizes for usage as aggregate and cement in concrete or mortar provides an effective and sustainable solution to environmental problems by reducing natural resource dependence. Numerous studies have attempted to analyze the suitability of waste seashell as a possible alternative to natural aggregates and cement in concrete or mortar. This paper presents an up-to-date review of the characteristics of different types of waste seashell, as well as the physical, mechanical, durability, and other notable functional properties of seashell concrete or mortar. From the outcome of the research, waste seashell could be an inert material, and it is important to conduct a series of proper treatment for a better-quality material. It is also seen from the results that although the mechanical properties of seashell concrete have been reduced, they all meet the required criteria set by various international standards and codes. Therefore, it is recommended that the replacement of seashells as aggregate and cement should not exceed 20% and 5%, respectively. Seashell concrete or mortar would then have sufficient workability and strength for non-structural purposes. However, there is still a lack of investigation concerning the different properties of reinforced concrete members using seashells as the replacement of aggregate or cement. Further innovative research can solidify its utilization towards sustainable development.

Stearate-Coated Biogenic Calcium Carbonate from Waste Seashells: A Sustainable Plastic Filler.

Waste seashells from aquaculture are a massive source of biogenic calcium carbonate (bCC) that can be a potential substitute for ground calcium carbonate and precipitated calcium carbonate. These last materials find several applications in industry after a surface coating with hydrophobic molecules, with stearate as the most used. Here, we investigate for the first time the capability of aqueous stearate dispersions to coat bCC powders from seashells of market-relevant mollusc aquaculture species, namely the oyster Crassostrea gigas, the scallop Pecten jacobaeus, and the clam Chamelea gallina. The chemical-physical features of bCC were extensively characterized by different analytical techniques. The results of stearate adsorption experiments showed that the oyster shell powder, which is the bCC with a higher content of the organic matrix, showed the highest adsorption capability (about 23 wt % compared to 10 wt % of geogenic calcite). These results agree with the mechanism proposed in the literature in which stearate adsorption mainly involves the formation of calcium stearate micelles in the dispersion before the physical adsorption. The coated bCC from oyster shells was also tested as fillers in an ethylene vinyl acetate compound used for the preparation of shoe soles. The obtained compound showed better mechanical performance than the one prepared using ground calcium. In conclusion, we can state that bCC can replace ground and precipitated calcium carbonate and has a higher stearate adsorbing capability. Moreover, they represent an environmentally friendly and sustainable source of calcium carbonate that organisms produce by high biological control over composition, polymorphism, and crystal texture. These features can be exploited for applications in fields where calcium carbonate with selected features is required.

Ethanolysis of Cao-Base Derived from Seashell for Conversion of Waste Used Oil for Biodiesel Production

The physicochemical properties of the waste used oil (WUO) were carried out for biodiesel production. The heterogenous catalyst (CAO based) used in this work was derived from waste seashell. The produced biodiesel was characterized and the optimum biodiesel produced was determined through statistical analysis. This was with a view to add value to the WUO and finding the solution to reduction of the excess carbon release to the environment. According to the results obtained, it showed that the refined WUO properties were in line with oil property requirement for biodiesel production. The physicochemical characteristics of the WUO showed physical state of the oil to be liquid/dark brownish at 28 oC, viscosity 6.58 cP at 28 oC, acid value, 0.96 (mg KOH/g oil), FFA (% oleic acid), 0.48, iodine value, 152.00 (g I2/100g oil), peroxide value, 5.1 milli-equivalent of peroxide/kg of oil among others. The derived catalyst showed high basic strength with potassium oxide (61.63 wt.%) as the dominant element in the catalyst. Optimum biodiesel yield was obtained at run 5 with 98.52 (%wt./wt.) at reaction time of 65 min, catalyst amount of 4.0 (%wt.), reaction temperature of 70 oC, and ethanol-oil molar ratio of 7:1. The produced biodiesel properties was compared with the recommended standard ASTM D6751 and EN 14214.

Valorization of bio‐calcium carbonate based Chamelea gallina shell waste fillers in shape memory polymer composites

AbstractIn recent years, the focus has been on the use of calcium carbonate‐based seashell wastes in the production of new thermoplastic and thermoset polymer materials, paving the way for their use as biofillers in polymeric composites. In this study, it is aimed to obtain a new polymeric composite material by doping Chamelea gallina shells, on polylactic acid (PLA)/polyethylene glycol (PEG) blend. Structural characterization of the obtained PLA/PEG blend/C. gallina composite films was performed with attenuated total reflection infrared spectroscopy (ATR‐IR). When the thermal properties of composite materials were examined by thermogravimetric analysis (TGA), it was determined that the thermal stability of polymeric composites increased with the addition of C. gallina. SEM images showed that the polymer blend films, which appeared to have a porous structure, filled the pores with increasing C. gallina ratio. It was observed that the biodegradability of PLA/PEG blend composite films decreased with increasing C. gallina shells addition. However, C. gallina had a positive effect on the swelling and water absorption capacities of polymeric composites. The increase in tensile strength and elongation at break values of PLA/PEG blend/C. gallina composite films with increasing C. gallina means that the mechanical properties of the polymer are improved.

Synthesis and characterization of hydroxyapatite self-assembled nanocomposites on graphene oxide sheets from seashell waste: A green process for regenerative medicine

Bone transplantation is the second most common transplantation surgery in the world. Therefore, there is an urgent need for artificial bone transplantation to repair bone defects. In bone tissue engineering, hydroxyapatite (HA) plays a major role in bone graft applications. This study deals with a facile method for synthesizing HA hexagonal nanorods from seashells by a solid-state hydrothermal transition process. The synthesized HA nanorods (∼2.29 nm) were reinforced with carbon nanotube and chitosan on graphene oxide sheets with polymeric support by in-situ synthetic approach. Among the synthesized nanocomposites viz., hydroxyapatite-graphene oxide (HA-GO), hydroxyapatite-graphene oxide-chitosan (HA-GO-CS), hydroxyapatite-graphene oxide-chitosan-carbon nanotube-polylactic acid (HA-GO–CS–CNT-PLA). Among them, the HA-GO–CS–CNT-PLA composite exhibits micro and macro porosity (∼200 to 600 μm), higher mechanical strength, (Hardness ∼90.5 ± 1.33 MPa; Tensile strength 25.62 MPa), and maximum cell viability in MG63 osteoblast-like cells (80%). The self-assembled hybrid-nanocomposite of HA-GO–CS–CNT-PLA is a promising material for bone filler application and could efficiently utilize seashell waste through the green process.

Green synthesis of lactic acid and carbon dots using food waste and seashell waste

Novel utilisation of seashell waste in lactic acid fermentation, showcasing fluorescent carbon quantum dots synthesised from cell biomass.