CO2 sequestration in microbial electrolytic cell-anaerobic digestion system combined with mineral carbonation for sludge hydrolysate treatment

The combination of microbial electrolytic cells and anaerobic digestion (MEC-AD) became an efficient method to improve CO2 capture for waste sludge treatment. By adding CaCl2 and wollastonite, the CO2 sequestration effect with mineral carbonation under 0 V and 0.8 V was studied. The results showed that applied voltage could increase dissolved chemical oxygen demand (SCOD) degradation efficiency and biogas yield effectively. In addition, wollastonite and CaCl2 exhibited different CO2 sequestration performances due to different Ca2+ release characteristics. Wollastonite appeared to have a better CO2 sequestration effect and provided a wide margin of pH change, but CaCl2 released Ca2+ directly and decreased the pH of the MEC-AD system. The results showed methane yield reached 137.31 and 163.50 mL/g SCOD degraded and CO2 content of biogas is only 12.40 % and 2.22 % under 0.8 V with CaCl2 and wollastonite addition, respectively. Finally, the contribution of chemical CO2 sequestration by mineral carbonation and biological CO2 sequestration by hydrogenotrophic methanogenesis was clarified with CaCl2 addition. The chemical and biological CO2 sequestration percentages were 46.79 % and 53.21 % under 0.8 V, respectively. With the increased applied voltage, the contribution of chemical CO2 sequestration rose accordingly. The findings in this study are of great significance for further comprehending the mechanism of calcium addition on CO2 sequestration in the MEC-AD system and providing guidance for the later engineering application.

Utilization of wollastonite, jarosite, and their blends for the sustainable development of concrete paver block mixes containing reclaimed asphalt pavement aggregates

While several research studies considered the utilization of reclaimed asphalt pavement (RAP) aggregates for asphalt and concrete pavements, very few attempted its possible utilization for precast concrete applications like concrete paver blocks (CPBs). Moreover, few attempts made in the recent past to improve the strength properties of RAP inclusive concrete mixes by incorporating certain supplementary cementitious materials (SCMs) have reported an insignificant or marginal effect. The present study attempts to comprehensively investigate the utilization potential of some locally and abundantly available materials having suitable physicochemical properties to improve the performance of a zero-slump CPB mix containing 50% RAP aggregates. The studied filler materials, namely, wollastonite (naturally occurring calcium metasilicate mineral) and jarosite (hazardous zinc industry waste), were used to replace 5-15% and 10-20% by volume of Portland cement in the 50% RAP CPB mix. Apart from their individual effects, the efficacy of wollastonite-jarosite blends was also investigated. Considering the lack of indoor storage facilities and economic aspects of CPBs, the influence of water spray curing regime on the performance of the RAP CPB mixes was studied and compared to that of continuous water curing regime. Inclusion of the considered fillers was found to statistically and significantly enhance the flexural strength, tensile splitting strength, and abrasion resistance of the 50% RAP CPB mix; however, the compressive strength (in most cases), permeable voids, water absorption, and water permeability properties showed an insignificant improvement. Results of thermogravimetric analysis confirmed the occurrence of pozzolanic reactivity, and microstructure analysis revealed improvements in packing of concrete matrix and ITZ with filler inclusion qualitatively substantiating the improvements in strength and durability characteristics. The toxicity characteristics of heavy metals that may leach from the hazardous jarosite-based RAP CPB mixes were found to be within permissible limits. Based on the performance requirements specified by IS, IRC, and ASTM standards, all the RAP CPB mixes with filler inclusions fulfilled the acceptance criteria for heavy traffic applications, and water spray curing can enact as an alternate method for curing these mixes. However, to avail maximum performance benefits, it is recommended to use 5% wollastonite, 15% jarosite, and a combination of 10% wollastonite and 10% jarosite as a Portland cement substitute to produce sustainable eco-friendly RAP CPB mixes.

Zinc oxide calcium silicate composite attenuates acute tramadol toxicity in mice

BACKGROUND

Seizures are considered to be the most common symptom encountered in emergency- rushed tramadol-poisoned patients; accounting for 8% of the drug-induced seizure cases. Although, diazepam clears these seizures, the risk of central respiratory depression cannot be overlooked. Henceforth, three adsorbing composites were examined in a tramadol acute intoxication mouse model.

METHODS

Calcium Silicate (Wollastonite) either non-doped or wet doped with iron oxide (3%Fe₂O₃) or zinc oxide (30% ZnO) were prepared. The composites' adsorption capacity for tramadol was determined in vitro. Tramadol intoxication was induced in Swiss albino mice by a parenteral dose of 120 mg/kg. Proposed treatments were administered within 1 min at 5 increasing doses, i.p. The next 30 min, seizures were monitored as an intoxication symptom. Plasma tramadol concentration was recorded after two hours of administration.

RESULTS

The 3% Fe₂O₃-containing composite (CSFe3), was found to be composed of mainly wollastonite with very little alpha-hematite. On the other hand, hardystonite and wellimite were developed in the 30%ZnO-containing composite (CSZn3). Micro-round and irregular nano-sized microstructures were established (The particle size of CS was 56 nm, CSFe3 was 49 nm, and CSZn3 was 42 nm). The CSZn3 adsorption capacity reached 1497 mg of tramadol for each gram. Tramadol concentration was reduced in plasma and seizures were inhibited after its administration to mice at three doses.

CONCLUSION

The calcium silicate composite doped with ZnO presented a good resolution of tramadol-induced seizures accompanied by detoxification of blood, indicating its potential for application in such cases. Further studies are required.

Negatively charged nano-hydroxyapatite can be used as a phosphorus fertilizer to increase the efficacy of wollastonite for soil cadmium immobilization

Improper application of phosphorus (P) fertilizer during soil cadmium (Cd) immobilization reduces the efficiency of fertilizer and Cd remediation. In this study, we synthesized three types of nano-hydroxyapatite (NHAP) with different surface charges as slow-release P fertilizers during Cd immobilization. We also evaluated the effects of wollastonite application with or without NHAP addition, in comparison with triple superphosphate (TSP) or bulk hydroxyapatite, on Cd accumulation in Amaranthus tricolor L. The results showed that adding wollastonite significantly reduced P availability (23.5%) in the soil, but it did not inhibit plant P uptake. In wollastonite-amended soil, the application of negatively/positively charged NHAP significantly increased plant biomass by 643-865% and decreased Cd uptake by 74.8-75.1% compared to the unamended soil as well as showed greater efficiency than those with TSP. This was ascribed to the increased soil pH (from 3.94 to 6.52-6.63) and increased abundance of organic acids (including citric acid, malic acid, lactic acid, and acetic acid) secreted by plants. In addition, the P-preferring bacterial class Bacteroidia was specific to soils amended with both wollastonite and NHAP-. These results suggest that NHAP- may be an appropriate P fertilizer for soil Cd immobilization using wollastonite.

CO2 sequestration mediated by wollastonite in anaerobic digestion of sewage sludge: From sequence batch to semi-continuous operation

This study investigated the mechanisms involved in CO₂ sequestration under the sequence batch and semi-continuous operation using wollastonite in sludge anaerobic digestion. Wollastonite substantially elevated CH₄ content in biogas and played a role in CO₂ capture. It increased biogas yield of the glucose due to pH buffering effect but did not increase that of the hydrolysate from thermal alkali pretreated sludge. Under the semi-continuous operation, wollastonite improved the CO₂ sequestration, but decreased the biogas yield from 166 to 24 mL/g soluble chemical oxygen demand, since seemingly wollastonite residues inhibited microbes in the sludge. However, the use of dialysis bags to wrap wollastonite offset the negative impact of the wollastonite residues in the sludge, thereby increased biogas yield. The present study is conducive to understanding the mechanisms involved in and proving the feasibility of the CO₂ sequestration using wollastonite in sludge anaerobic digestion and its impacts on long-term operation. Consequently, the findings of the study provide key parameters and useful guidelines for scaling up and wollastonite application in anaerobic digestion of sewage sludge.

Fabrication of substituted hydroxyapatite-starch-clay bio-composite coated titanium implant for new bone formation

The clay/polymeric matrices have much attention from researchers in bio-medical applications due to their numerous uses. This study introduces new orthopedic titanium (Ti) implant with increasing bio-activity by treating the surface of the Ti implant with bio-compatible composite coating. Wollastonite (WST) clay combined minerals (Mg²⁺and Gd³⁺) substituted hydroxyapatite (HAP)/Starch composite was prepared using in-situ co-precipitation method. It was successfully coated on the orthopedic grade Ti plate by the Electrophoretic Deposition (EPD) method. The functionality, phase, morphology, and bio-activity analysis of the composite were evaluated by FT-IR, XRD, HR-TEM, and SEM analysis, respectively. The mechanical property, i.e., Vickers microhardness value of the MHAP/Starch/WST composite coated Ti plate, showed 242 ± 1.92 Hv. The in-vitro MG-63 osteoblast cells viability, differentiation, and Ca mineralization of MHAP/Starch/WST composite suggests that this new implant will be used for bone regeneration application after careful evaluation of in-vivo and clinical studies.

Effect of Na2O and ZnO on the microstructure and properties of laser cladding derived CaO-SiO2 ceramic coatings on titanium alloys

To improve the bioactivity of titanium alloy (Ti-6Al-4V), CaO-SiO₂ coatings on titanium alloys were fabricated using laser cladding method. The effect of Na₂O and ZnO on the microstructure and properties of the prepared coatings was discussed. The microstructure of the CaO-SiO₂ coatings consists of cellular grains and cellular dendrites. The mutual diffusion of elements occurs between the coating and substrate. The base CaO-SiO₂ coating is composed of different phases including CaTiO₃, α-Ca₂(SiO₄), SiO₂, TiO₂ and CaO. The formation of CaTiO₃ in the ceramic layer was analyzed through thermodynamics. Na₂O has little influence on the microstructure, average hardness and wear resistance. When ZnO is added to the precursor, the microstructure turns to cell dendrite, and ZnO and Zn₂SiO₄ appear in the corresponding coating. The addition of ZnO reduces the average hardness and wear resistance of the ceramic layer. The in vitro soaking in SBF shows that the laser cladding coating has the ability to form an apatite layer.

Characterisation of products from fungally modified wollastonite and the simulation experiment of Pb2+ fixation

Using cheap raw materials and simple biological modification methods to obtain modified materials to remediate heavy metals has potential application prospects. Here, Aspergillus niger was used to modify wollastonite and further explore its fixation capacity and mechanism. The results showed that the growth and metabolism of A. niger promoted the weathering of wollastonite and the synthesis of whewellite, forming a mineral composite through fungal modification (MCF) with excellent fixation properties of heavy metal Pb²⁺. The maximum adsorption capacity of MCF for Pb²⁺ (434.78 mg/g) is significantly greater than that of original wollastonite (11.86 mg/g) with a desired lower desorption rate. Additionally, its removal rate of Pb²⁺ is higher than 75% under varying acidic conditions (1 ≤ pH ≤ 5.5). The results of XRD, FTIR, BET specific surface area, and SEM-EDS showed that MCF has a special organic-inorganic composite structure, which imparts a larger contact area for ions, and efficient removal of Pb²⁺ through combined physico-chemical adsorption. Batch adsorption results also indicated that the adsorption process by MCF was mainly a spontaneous endothermic reaction in the monolayer. This study provides a new perspective for the bio-modification of wollastonite and its application in the remediation of heavy metal pollution.

Metal doped calcium silicate biomaterial for skin tissue regeneration in vitro

This study spots light on combined Wound healing process conjoining blood coagulation, inflammation reduction, proliferation and remodeling of the cells. The objective is to overcome the drawbacks of conventional clinically applied wound dressings such as poor rigidity, porosity, mechanical potency and bactericidal activity. As nosocomial infection is a very common condition at the wound site, bio-adhesive materials with intrinsic antibacterial properties are used in clinical applications. Considering the provenability of Wollastonite [Calcium silicate (CaSiO3)] to regenerate the soft tissues by inducing vascularization and regeneration of fibroblast cells And the antibacterial potentiality of zinc in clinical applications, the present study focuses on synthesis of Zn-Ws particles and evaluation of its antimicrobial and wound healing potentialities towards skin tissue engineering applications. The compositional characterization by EDAS and FT-IR spectral analysis have substantiated the presence of major elements and corresponding band stretching associated with the synthesized particles whereas the particles morphology by SEM images have shown the size of the Ws and Zn-Ws to be 370 nm and 530 nm respectively. From the in vitro studies, skin regenerative potential of Zn-Ws was determined on promoting fibroblast cell (NIH3T3) proliferation by providing better adhesiveness, biocompatibility and cytocompatibility. The antibacterial property of Zn-Ws evaluation by minimum inhibitory concentration (MIC) and zone of inhibition (ZOI) methods against clinical isolates of Gram +Ve and Gram -Ve bacterial strains have confirmed that the addition of Zn has diminished the bacterial growth and also helped in degrading the bacterial biofilms. Thus it is summed up that the process of wound healing is expected to occur with reduced risk of post-injury infections by the presence of zinc-doping on wollastonite for skin tissue application.

Carbon dioxide sequestration and methane production promotion by wollastonite in sludge anaerobic digestion

This study investigated the feasibility and performance of simultaneous in-situ CO₂ sequestration and CH₄ production promotion by wollastonite addition in sludge AD. A maximum CH₄ yield increment of 30.8% and maximum methane production rate increment of 64.9% with wollastonite addition at dosage of 16.25 g/L were achieved. CO₂ was efficient sequestered by wollastonite addition and resulted in a higher CH₄ content of 81.7%-82.4%. The mechanism of CO₂ sequestration by wollastonite was confirmed as Ca²⁺ release and subsequently carbonation based on cation and precipitates analysis. The results demonstrated that wollastonite could be applied as an effective additive for simultaneous in-situ CO₂ sequestration and CH₄ production promotion of sludge AD.

Phase pure, high hardness, biocompatible calcium silicates with excellent anti-bacterial and biofilm inhibition efficacies for endodontic and orthopaedic applications

Here we report for the very first time the synthesis of 100% phase pure calcium silicate nanoparticles (CSNPs) of the α-wollastonite phase without using any surfactant or peptizer at the lowest ever reported calcination temperature of 850 °C. Further, the phase purity is confirmed by quantitative phase analysis. The nano-network like microstructure of the CSNPs is characterized by FTIR, Raman, XRD, FESEM, TEM, TGA, DSC etc. techniques to derive the structure property correlations. The performance efficacies of the CSNPs against gram-positive e.g., S. pyogenes and S. aureus (NCIM2127) and gram-negative e.g., E. coli (NCIM2065) bacterial strains are studied. The biocompatibility of the CSNPs is established by using the conventional mouse embryonic osteoblast cell line (MC3T3). In addition, the biofilm inhibition efficacies of two varieties of CSNPs e.g., CSNPs(W) and CSNPs(WC) are investigated. Further, the interconnection between ROS e.g., superoxide (O₂^.-) and hydroxyl radical (^.OH) generation capabilities of CSNPs and their biofilm inhibition efficacies is clearly established for the very first time. Finally, the mechanical responses of the CSNPs at the microstructural length scale are investigated by nanoindentation. The results confirm that the α-wollastonite phases present in CSNPs(W) and CSNPs(WC) possess extraordinarily high nanohardness and Young's moduli values. Therefore, these materials are well suited for orthopaedic and endodontic applications.

Hydration of Concrete: The First Steps

Concrete is the most important construction material used by mankind and, at the same time, one of the most complex substances known in materials science. Since this mineral compound is highly porous, a better understanding of its surface chemistry, and in particular the reaction with water, is urgently required to understand and avoid corrosion of infrastructure like buildings and bridges. We have gained insight into proton transfer from concrete upon contact with water by applying the so-called Surface Science approach to a well-defined mineral, Wollastonite. Data from IR (infrared) spectroscopy reveal that exposure of this calcium-silicate (CS) substrate to H₂ O leads to dissociation and the formation of OH-species. This proton transfer is a chemical reaction of key importance, since on the one hand it triggers the conversion of cement into concrete (a calcium-silicate-hydrate phase), but on the other hand also governs the corrosion of concrete. Interestingly, we find that no proton transfer takes place when the same surface is exposed to methanol. In order to understand this unexpected difference, the analysis of the spectroscopic data obtained was aided by a detailed, first-principles computational study employing density functional theory (DFT). The combined experimental and theoretical effort allows derivation of a consistent picture of proton transfer reactions occurring in CS and CSH phases. Implications for strategies to protect this backbone of urban infrastructure from corrosion in harsh, aqueous environments will be discussed.

Reconstruction of radial bone defect in rat by calcium silicate biomaterials

AIMS

Despite many attempts, an appropriate therapeutic method has not yet been found to enhance bone formation, mechanical strength and structural and functional performances of large bone defects. In the present study, the bone regenerative potential of calcium silicate (CS) biomaterials combined with chitosan (CH) as calcium silicate/chitosan (CSC) scaffold was investigated in a critical radial bone defect in a rat model.

MAIN METHODS

The bioimplants were bilaterally implanted in the defects of 20 adult Sprague-Dawley rats. The rats were euthanized and the bone specimens were harvested at the 56th postoperative day. The healed radial bones were evaluated by three-dimensional CT, radiology, histomorphometric analysis, biomechanics, and scanning electron microscopy.

KEY FINDINGS

The XRD analysis of the CS biomaterial showed its similarity to wollastonite (β-SiCO₃). The degradation rate of the CSC scaffold was much higher and it induced milder inflammatory reaction when compared to the CH alone. More bone formation and higher biomechanical performance were observed in the CSC treated group in comparison with the CH treated ones in histological, CT scan and biomechanical examinations. Scanning electron microscopic observation demonstrated the formation of more hydroxyapatite crystals in the defects treated with CSC.

SIGNIFICANCE

This study showed that the CSC biomaterials could be used as proper biodegradable materials in the field of bone reconstruction and tissue engineering.

Comparative investigations of structure and properties of micro-arc wollastonite-calcium phosphate coatings on titanium and zirconium-niobium alloy

Investigation results of micro-arc wollastonite–calcium phosphate (W–CaP) biocoatings on the pure titanium (Ti) and Zr–1wt.%Nb (Zr–1Nb) alloy were presented. The voltages of 150–300 V generate the micro-arc oxidation (MAO) process with the initial amplitude current of 150–550 A and 100–350 A for Ti and Zr–1Nb substrates, respectively. The identical dependencies of changes of the coating thickness, surface roughness and adhesion strength on the process voltage were revealed for the both substrates. The W–CaP coatings with the thickness of 10–11 μm were formed on Ti and Zr–1Nb under the low process voltage of 130–150 V. Elongated wollastonite particles with the size in the range of 40–100 μm were observed in such coatings. The structure of the coatings on Ti was presented by the X–ray amorphous and crystalline phases. The X–ray reflexes relating to the crystalline phases of Ti and wollastonite were observed only in XRD patterns of the coatings deposited under 130–200 V on Ti. While, the crystalline structure with phases of CaZr₄(PO₄)₆, β–ZrP₂O₇, ZrO₂, and Zr was detected in the coatings on Zr–1Nb. FT–IRS, XRD, SEM, and TEM data confirmed that the increase of the process voltage to 300 V leads to the dissociation of the wollastonite. No toxic effect of specimens on a viability, morphology and motility of human adipose–derived multipotent mesenchymal stem cells was revealed in vitro.

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Investigations of microarc wollastonite–calcium phosphate biocoatings on the titanium and Zr–1wt.%Nb alloy were presented.

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The thin coatings 10–11 μm with wollastonite particles formed under the low process voltage of 130–150 V.

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The increase of the process voltage to 300 V leads to the dissociation of the wollastonite.

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Coatings on both substrates have not toxic effect on the morphofunctional status of AMMSCs culture in vitro.

Antibacterial activity of agricultural waste derived wollastonite doped with copper for bone tissue engineering

Bioactive ceramic materials with metal ions generation brought great attention in the class of biomaterials development and widely employed as a filler material for bone tissue regeneration. The present study aimed to fabricate calcium silicate based ceramic material doped with copper metal particles by sol-gel method. Rice straw of agricultural waste was utilized as a source material to synthesize wollastonite, then wollastonite was doped with copper to fabricate copper doped wollastonite (Cu-Ws) particles. The synthesized materials were subjected to physio-chemical characterization by TEM, DLS, FTIR, XRD and DSC analysis. It was found that the sizes of the WS particles was around 900nm, while adding copper the size was increased upto 1184nm and the addition of copper to the material sharpening the peak. The release of Cu ions was estimated by ICP analysis. The anti-bacterial potentiality of the particles suggested that better microbial growth inhibition against E. coli (Gram negative) and S. aureus (Gram positive) strains from ATCC, in which the growth inhibition was more significant against S. aureus. The biocompatibility in mouse Mesenchymal Stem cells (mMSC) showed the non-toxic effect up to 0.05mg/ml concentration while the increase in concentration was found to be toxic to the cells. So the particles may have better potential application with the challenging prevention of post implantation infection in the field of bone tissue engineering (BTE).

Biodegradable ceramic-polymer composites for biomedical applications: A review

The present work focuses on the state-of-the-art of biodegradable ceramic-polymer composites with particular emphasis on influence of various types of ceramic fillers on properties of the composites. First, the general needs to create composite materials for medical applications are briefly introduced. Second, various types of polymeric materials used as matrices of ceramic-containing composites and their properties are reviewed. Third, silica nanocomposites and their material as well as biological characteristics are presented. Fourth, different types of glass fillers including silicate, borate and phosphate glasses and their effect on a number of properties of the composites are described. Fifth, wollastonite as a composite modifier and its effect on composite characteristics are discussed. Sixth, composites containing calcium phosphate ceramics, namely hydroxyapatite, tricalcium phosphate and biphasic calcium phosphate are presented. Finally, general possibilities for control of properties of composite materials are highlighted.

Synergistic improvement of crop physiological status by combination of cadmium immobilization and micronutrient fertilization

Wollastonite application in cadmium-contaminated soils can reduce cadmium concentrations in plant, while the side effect is the synchronous immobilization of micronutrients, which reduces micronutrient uptake in plant, inducing micronutrient deficient symptoms. Accordingly, we investigated whether the supplement of Zn and Mn fertilizers after the wollastonite addition could promote the growth and photosynthesis in amaranth (Amaranthus tricolor L.). In this study, plants were cultivated in cadmium-contaminated soil under micronutrient fertilization alone, wollastonite addition, and combination of wollastonite and micronutrient fertilization treatments. Then, plant biomass; photosynthesis parameters; and total Cd, Zn, and Mn concentrations were investigated. Moreover, chemical extractions were performed on soil samples. The results show that application of wollastonite decreased Cd, Zn, and Mn concentrations in plant and availability in soil and it increased the gas exchange ability of plants. But, it reduced the chlorophyll content in leaves and had no positive influence on plant biomass. In comparison, Zn and Mn fertilization after wollastonite application greatly increased plant biomass and photosynthetic ability. It also reduced Cd phytoavailability more efficiently. Therefore, synergistic improvement of physiological status of farmland crop by sequential treatment with first wollastonite for cadmium immobilization, and then micronutrient fertilization to avoid micronutrient deficiency, was demonstrated.

Isolation of a wide range of minerals from a thermally treated plant: Equisetum arvense, a Mare's tale

Silica is the second most abundant biomineral being exceeded in nature only by biogenic CaCO3. Many land plants (such as rice, cereals, cucumber, etc.) deposit silica in significant amounts to reinforce their tissues and as a systematic response to pathogen attack. One of the most ancient species of living vascular plants, Equisetum arvense is also able to take up and accumulate silica in all parts of the plant. Numerous methods have been developed for elimination of the organic material and/or metal ions present in plant material to isolate biogenic silica. However, depending on the chemical and/or physical treatment applied to branch or stem from Equisetum arvense; other mineral forms such glass-type materials (i.e. CaSiO3), salts (i.e. KCl) or luminescent materials can also be isolated from the plant material. In the current contribution, we show the chemical and/or thermal routes that lead to the formation of a number of different mineral types in addition to biogenic silica.

The Micro-mechanism Involved and Wollastonite Signature in the Calcareous Precipitates of Marine Isolates

Micro-mechanical studies connecting the influence of extrinsic factors over intrinsic factors on 30 calcareous isolates obtained from marine sediment biofilms of the Bay of Bengal (Indian Ocean) revealed that the fate of calcareous crystal precipitation is highly dependent on factors like extracellular polysaccharides (EPS), organic carbon and nutrition. Further studies exemplified that EPS and the organic carbon secreted by the isolates controlled the dissemination of the calcareous crystals precipitated. From the study, it is evident that an EPS concentration of 7-15 mg l(-1) was found to enhance the dissemination of the calcareous crystals. Atomic force micrographs explain the nucleation behaviour and morphology of the calcareous crystals precipitated. X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDAX) showed that the crystals were mainly composed of calcite and partially wollastonite.

Recovery of volatile fatty acids from fermentation of sewage sludge in municipal wastewater treatment plants

This work investigated the pilot scale production of short chain fatty acids (SCFAs) from sewage sludge through alkaline fermentation and the subsequent membrane filtration. Furthermore, the impact of the fermentation liquid on nutrient bioremoval was examined. The addition of wollastonite in the fermenter to buffer the pH affected the composition of the carbon source produced during fermentation, resulting in higher COD/NH4-N and COD/PO4-P ratios in the liquid phase and higher content of propionic acid. The addition of wollastonite decreased the capillary suction time (CST) and the time to filter (TTF), resulting in favorable dewatering characteristics. The sludge dewatering characteristics and the separation process were adversely affected from the use of caustic soda. When wollastonite was added, the permeate flux increased by 32%, compared to the use of caustic soda. When fermentation liquid was added as carbon source for nutrient removal, higher removal rates were obtained compared to the use of acetic acid.

Valorization of sugarcane bagasse ash: producing glass-ceramic materials

Some aluminosilicates, for example mullite and wollastonite, are very important in the ceramic and construction industries. The most significant glass-ceramic for building applications has wollastonite as the main crystal phase. In this work we report on the use of sugarcane bagasse ash (SCBA) to produce glass-ceramics with silicates as the major crystalline phases. The glasses (frits) were prepared by mixing ash, limestone (calcium and magnesium carbonates) and potassium carbonate as the fluxing agent. X-ray fluorescence was used to determine the chemical composition of the glasses and their crystallization was assessed by using thermal analysis (DTA/DSC/TGA) and X-ray diffraction. The results showed that glass-ceramic material can be produced with wollastonite as the major phase, at a temperature lower than 900 °C.