Conventional Hydrothermal Treatment Research Articles

Comparative study of TiO2–Fe3O4 photocatalysts synthesized by conventional and microwave methods for metronidazole removal

This study focused on a direct comparison of conventional hydrothermal and microwave treatment during the synthesis of TiO2–Fe3O4 photocatalyst, which is an effective catalyst for decomposing metronidazole. The photocatalyst underwent various characterization analyses, including X-ray diffraction, Raman spectroscopy, transmission electron microscopy, energy dispersive X-ray, and diffuse reflectance spectroscopy. The Raman spectroscopy analysis revealed that the materials obtained through the conventional hydrothermal treatment consisted of separate phases of anatase and magnetite. On the other hand, the materials synthesized using the microwave process showed a noticeable shift in the Eg band (143 cm−1) and its half-width towards higher wavenumbers. This shift is likely due to the introduction of Fe ions into the TiO2 lattice. Additionally, both conventional hydrothermal and microwave synthesis routes produced TiO2–Fe3O4 systems with superparamagnetic properties, as demonstrated by SQUID magnetic measurements. The TEM analysis revealed that the materials synthesized using the microwave process exhibited higher homogeneity, with no noticeable large aggregates observed. Finally, this work proposed a convenient LED photoreactor that effectively utilized the photo-oxidative properties of TiO2–Fe3O4 photocatalysts to remove metronidazole. Combining photoactive TiO2–Fe3O4 catalysts with an energy-efficient LED reactor resulted in a low electrical energy per order (EEO).

Formation of a calcium hydrogen phosphate coating on AZ41 magnesium alloy by ultrasound-assisted chemical conversion for concrete formwork

The poor anticorrosion property of magnesium alloys is one of main concerns prior to their various applications. In this study, an anticorrosive hydrogen phosphate coating was fabricated via the ultrasound-assisted chemical conversion treatment on AZ41 Mg alloy for concrete formwork. The coatings prepared by the conventional chemical conversion and hydrothermal treatment were also obtained as a comparison. Surface characterizations and electrochemical methods were carried out. Results show that the ultrasound-assisted coating obtained possesses a thickness more than 3 μm, which is thicker than the other two coatings. Moreover, the ultrasound-assisted coating presents a more homogeneous structure on the second phases, while the surface qualities of the other two coatings were significantly reduced due to the inhomogeneous CaHPO4·2H2O (DCPD) formed on the second phases in AZ41 Mg alloy. The ultrasound-assisted chemical conversion coating exhibits a good corrosion resistance even comparable to the hydrothermal coating. It exhibits a corrosion current density on the order of magnitude of 10−7 A·cm−2 even after the embedment of 96 h in the Portland cement (PC) system containing 3.5 wt% NaCl.

Microwave assisted and conventional hydrothermal treatment of waste seaweed: Comparison of hydrochar properties and energy efficiency

Waste seaweed is a valuable source for converting into value-added carbon materials. In this study, the production of hydrochar from waste seaweed was optimized for hydrothermal carbonization in a microwave process. The produced hydrochar was compared with hydrochar synthesized by the regular process using a conventional heating oven. The results show that hydrochar produced with a holding time of 1 h by microwave heating has similar properties to the hydrochar produced in a conventionally heated oven for 4 h (200 °C and water/biomass ratio 5): carbon mass fraction (52.4 ± 3.9 %), methylene blue adsorption capacity (40.2 ± 0.2 mg g−1) and similar observations on surface functional groups and thermal stability were made between hydrochars produced by both methods. The analysis of energy consumption showed microwave assisted carbonization consume higher energy in compare to conventional oven.The present results suggest that hydrochar made from waste seaweed and using the microwave technique could be an energy-saving technology for producing hydrochar with similar specifications to hydrochar produced by conventional heating methods.

Manufacturing of hemicellulosic oligosaccharides from fast-growing Paulownia wood via autohydrolysis: Microwave versus conventional heating

Microwave hydrothermal treatment (MHT) is considered a sustainable technology for the valorization of lignocellulosic materials, enabling the solubilization of hemicellulosic-derived compounds, especially in the form of oligosaccharides that may present potential in the chemical, pharmaceutical or nutraceutical industries. Hence, MHT at 200 and 230 °C, at severity (S 0 ) among 2.92–4.66 were performed. S 0 = 3.98 permitted the recovery of about 80% of the initial xylan as xylooligosaccharides. In order to compare the effectiveness of MHT, conventional hydrothermal treatment (CHT) was performed at conditions leading to the maximum recovery of oligosaccharides (S 0 =3.98, non-isothermal regime at 203 °C). Despite the structural features of oligomers in the three liquors were very similar, the spent solids presented different enzymatic digestibility, which implied a different effect of the treatments, reaching up to 80% of glucan to glucose conversion for the solid after MHT at 230 °C for 0.5 min. Additionally, CHT consumed 2.1–2.8-fold greater energy than MHT, reflecting that microwave-assisted autohydrolysis is a sustainable and efficient technology to process PW. • Microwave (MHT) and conventional (CHT) hydrothermal treatments were evaluated. • Up to 80% xylan conversion into xylooligosaccharides via hydrothermal treatments. • Polyphenolic profile of Paulownia extracts was identified via HPLC-ESI-MS. • Glucose conversions of 64–80% after saccharification of MHT and CHT solids. • Up to 64.7% energy is saved using MHT comparing to CHT.

Upcycling of spent LiCoO2 cathodes via nickel‐ and manganese‐doping

AbstractDirect recycling has been regarded as one of the most promising approaches to dealing with the increasing amount of spent lithium‐ion batteries (LIBs). However, the current direct recycling method remains insufficient to regenerate outdated cathodes to meet current industry needs as it only aims at recovering the structure and composition of degraded cathodes. Herein, a nickel (Ni) and manganese (Mn) co‐doping strategy has been adopted to enhance LiCoO2 (LCO) cathode for next‐generation high‐performance LIBs through a conventional hydrothermal treatment combined with short annealing approach. Unlike direct recycling methods that make no changes to the chemical composition of cathodes, the unique upcycling process fabricates a series of cathodes doped with different contents of Ni and Mn. The regenerated LCO cathode with 5% doping delivers excellent electrochemical performance with a discharge capacity of 160.23 mAh g−1 at 1.0 C and capacity retention of 91.2% after 100 cycles, considerably surpassing those of the pristine one (124.05 mAh g−1 and 89.05%). All results indicate the feasibility of such Ni–Mn co‐doping‐enabled upcycling on regenerating LCO cathodes.

Circular conversion of waste rectorite@dye to efficient and pH-resistant heterogeneous silicate adsorbents for cyclic and complete dye removal

A series of new heterogeneous silicate adsorbents were synthesized from waste dye-adsorbed rectorite (named as rectorite@dye) through conventional calcination, hydrothermal treatment and an upgraded oxidation-promoted conversion process. Compared with conventional calcination and direct hydrothermal treatment processes, the positive effect of oxidants such as hydrogen peroxide and calcium peroxide on improving the conversion efficiency of rectorite@dye waste and adsorption properties was studied. It was revealed that hydrogen peroxide promoted the conversion of waste rectorite@dye into a heterogeneous rectorite@carbon composite with a carbon content of 1.38% and nitrogen content of 0.44%. The optimal rectorite@carbon adsorbent can efficiently adsorb Methylene blue at 176.77 mg/g and Basic red 14 at 305.87 mg/g, which shows superior performance than rectorite@dye (44.26 mg/g for Methylene blue; and 25.26 mg/g for Basic red 14) and composite adsorbents prepared by conventional calcination (141.52 mg/g for Methylene blue; 213.03 mg/g for Basic red 14) or direct hydrothermal treatment (74.47 mg/g for Methylene blue and 88.34 mg/g for Basic red 14). The adsorption capacity of the adsorbent is pH-independent, and it can be used over a wide pH range. Moreover, the composite adsorbents can remove 99.99% of Methylene blue and 99.90% of Basic red 14 from an initial 100 mg/L dye solution, and thus clean water was obtained after treating dye-polluted water with the rectorite@carbon adsorbents. After each adsorption cycle, the waste adsorbent can be regenerated by a one-step calcination or hydrothermal process and reused, and the adsorption capacity of the regenerated adsorbent can still reach 198.43 mg/g (for calcination regeneration) and 268.35 mg/g (for hydrothermal regeneration) after 6 regenerations.

Decrease the effective temperature of hydrothermal treatment for sewage sludge deep dewatering: Mechanistic of tannic acid aided

The formation of refractory compounds and high nitrogen concentrations in filtrates is the bottleneck of hydrothermal treatment (HT) for sludge deep dewatering. To simultaneously solve these two problems, tannic acid (TA)-aided HT was firstly developed in this study. TA addition improved dewaterability under all investigated HT temperatures by improving the sludge relative hydrophobicity. Moreover, the effective HT temperature was reduced from 180 to 160 ℃. The soluble extracellular polymeric substances (S-EPSs) of the sludge hydrothermally treated at 160 ℃ under the optimal TA dose (0.15 mmol/g total solids) contained 47.27% less total organic nitrogen than the S-EPSs of the raw sludge. This result means that the corresponding filtrate contained lower concentrations of refractory compounds and nitrogen than those under the conventional HT conditions and thus could be more easily treated. Furthermore, the changes in the protein secondary structure and the interaction of TA with high-molecular-weight (HMW) proteins in S-EPSs were found to be highly relevant (p < 0.05) to the improvement of sludge dewaterability. With increasing HT temperature (120–180 ℃), the S-EPS HMW proteins with numerous hydrophilic functional groups (hydroxyl and carboxyl) were hydrolyzed, and their secondary structures unfolded; consequently, more sites were exposed for hydrophobic binding with TA, and the TA–protein interaction was more stable and spontaneous. The precipitation of protein with TA also increased with the HT temperature. Thus, TA-aided HT improves protein precipitation and sludge dewaterability through protein structure destruction and the production of more hydrophobic binding sites for TA. The identification of the influencing mechanisms on SS EPS–TA interaction mode and binding capacity are conducive to the further upgrading of TA-aided HT for engineering applications.

Preparation and characterization of zeolite from waste Linz-Donawitz (LD) process slag of steel industry for removal of Fe3+ from drinking water

Cubical-shaped zeolite A was synthesized from the Linz-Donawitz (LD) process slag of the Steel Industry, utilizing conventional fusion-assisted hydrothermal treatment. Morphological and Physico-chemical characterizations were performed by various characterization techniques. A weight ratio of 1:1.2 (LD-slag: NaOH) was maintained during fusion, which provides a better binding effect with better mechanical stability to the zeolite framework. Fe3+ adsorption studies were performed at 273, 298, 303, and 308 K, respectively, within the range of 10–40 mg L−1 Fe3+ ion concentration for kinetic and isotherm studies. A maximum adsorption capacity of 27.55 mg g−1 was obtained at a 1.4 g L−1 adsorbent dosage, with 99.99% Fe3+ ion removal. Moreover, the Fe3+ adsorption study obeyed the pseudo-second-order kinetic model, whereas multistage diffusion controlled the adsorption process. Langmuir isotherm model best fitted the equilibrium data suggesting the highly negative charge over the adsorbent surface played a vital role in the electrostatic attraction of Fe3+ ions. Isomorphic replacement of silicon by aluminum ion imparted a highly negative charge over the zeolite surface in the primary structure unit. For real-life sample drinking water, the Fe3+ ion removal efficiency increases to 97.7%.

Implementation of hierarchically porous zeolite-polymer membrane for Chromium ions removal

This work deals with the preparation of a zeolite/polymer flat sheet membrane with hierarchical porosity and ion-exchange properties. The performance of the prepared membrane was examined by the removal of chromium ions from simulated wastewater. A NaY zeolite (crystal size of 745.8 nm) was prepared by conventional hydrothermal treatment and fabricated with polyethersulfone (15% PES) in dimethylformamide (DMF) to obtain an ion-exchange ultrafiltration membrane. The permeate flux was enhanced by increasing the zeolite content within the membrane texture indicating increasing the hydrophilicity of the prepared membranes and constructing a hierarchically porous system. A membrane containing 0.8% zeolite gave the higher %Rejection of chromium ions (about 83.2%) for an initial chromium ion concentration of 150 ppm and trans-membrane pressure of 1 bar.

Concentration-dependent emissive lignin-derived graphene quantum dots for bioimaging and anti-counterfeiting

Graphene quantum dots (GQDs) derived from lignin, which is the most naturally abundant aromatic biopolymer on earth, have found promising application in many fields. Here, we demonstrate that GQDs with concentration-dependent photoluminescence emission can be produced from lignin by employing a non-oxidative method. In brief, o-aminobenzenesulfonic acid was used as an acidic hydrotrope for lignin depolymerization, followed by a conventional hydrothermal treatment. Detailed investigations indicated that the observed concentration-dependent feature for GQDs was attributed to the stack of graphene basal plane and the interaction of functional groups. Moreover, it was found that the concentration-dependent emissive GQDs were endowed with ultralong-term photostability (12 months) and negligible cytotoxicity, promising them potential applications in anti-counterfeiting and bioimaging. Overall, this study develops a feasible and sustainable strategy for opening up enormous opportunities to use renewable lignin-derived GQDs for more technological applications.

Influence of process parameters on hydrothermal modification of soybean residue: Insight into the nutrient, solid biofuel, and thermal properties of hydrochars

Soybean (SB) solid residue after oil extraction was investigated in a hydrothermal modification process to provide an eco-friendly solution to SB solid waste disposal for an actual environmental management effort. SB hydrochars (HCs) were derived either by conventional heating hydrothermal treatment (HTT) under intense conditions (200, 250, and 300 °C for 2 h) or by microwave-assisted hydrothermal treatment (MHTT) under mild conditions (160, 190, and 220 °C for 1 h). Physicochemical properties of SB HCs and the transformation of nitrogen (N) and phosphorus (P) functionalities during HTT and MHTT were characterized using several tools. Ultimate and XPS analyses elucidated N transformation, e.g., 5.51 wt % N of raw SB residue decreased to 3.48 and 3.51 wt % after HTT and MHTT, respectively. The P bioavailability of raw SB (3.46 mg/g) was improved after HTT (26.7 mg/g) and MHTT (10.9 mg/g), depicting the practical application of HCs for soil amendment. Atomic H/C and O/C ratios of SB HCs decreased as treatment temperature increased. HCs showed credible higher heating value (HHV; 22.3–25.5 MJ/kg for HTT and 20.5–22.1 MJ/kg for MHTT), higher than various low-rank coals. Besides, energy densification and fuel ratio improved in intense conditions. The thermogravimetric analysis showed HCs possessed better thermal stability. The improved performance of SB HCs indicated that HTT and MHTT provided a green environmental route of SB waste management, valorization, and utilization.

A Comparative Study on Mesoporous Y Zeolites Prepared by Hard-Templating and Post-Synthetic Treatment Methods

Mesoporous Y zeolites were prepared comparatively using the bottom-up templating (with carbon nanotubes, CNTs, and nanocrystalline cellulose, NCC, as the templates) and the top-down post-synthetic treatment (with the sequential chemical and alkaline treatment) methods and characterised comprehensively using various techniques. The relevant findings show that the mesoporous Y zeolites with the intercrystal mesoporosity were prepared by the templating methods, and the NCC is the more effective, economic and sustainable hard template than the CNTs for promoting the formation of intercrystal mesoporosity. While for the post-synthetic strategy, the microwave (MW)-assisted chemical treatment (using ethylenediaminetetraacetic acid, EDTA, as the chemical agent for dealumination) was much more effective than the conventional hydrothermal (HT) treatment for introducing intracrystalline mesoporosity under the comparable condition, e.g. the external surface area: 287 m2 g−1 by 1 min MW treatment vs. 205 m2 g−1 by 6 h HT treatment. The prepared mesoporous Y zeolites, along with the parent Y, were assessed using the catalytic cracking of 1,3,5 triisopriopylbenzene (TiPBz). It was found that the well-developed intracrystalline mesoporosity promoted by the effective MW-assisted post-synthesis method is highly beneficial to the catalysis involving the bulky molecules, and accordingly showed the comparatively best catalytic performance (regarding the conversion and selectivity) among all zeolites under study in this work.

Alternative ball-milling synthesis of vanadium-substituted polyoxometalates as catalysts for the aerobic cleavage of C-C and C-O bonds.

Vanadium-substituted phosphomolybdic acids (H3+x[PMo12-xVxO40], denoted as Vx) are well-known oxidation catalysts that are generally prepared by the hydrothermal treatment of MoO3 and V2O5 in the presence of H3PO4. This synthesis procedure is highly energy consuming and the Vx yields are not always acceptable. In the present work, an alternative hybrid mechanochemical/hydrothermal synthesis of Vx is proposed, comprising the ball-milling of MoO3 and V2O5, followed by a hydrothermal attack. The resulting materials, with 2 ≤ x ≤ 3, obtained from this new route were compared, in terms of yield, energy consumption and catalytic activity, with a reference V3 sample prepared through a conventional hydrothermal treatment. The ball-milling step proved to lead not only to a shorter and far more energy-saving synthesis procedure, but also to high yields of Vx. Moreover, Vx from this alternative route proved to be generally more active than the conventionally prepared V3 in the aerobic oxidative cleavage of C-O and C-C bonds in 2-phenoxyacetophenone, used herein as a lignin model compound.

Hydrothermal treatments of walnut shells: A potential pretreatment for subsequent product obtaining

Walnuts are nowadays widely consumed. Since the edible part of walnuts does not account more than 50–60% of their total weight, the total amount of shells produced annually is huge. However, as walnut shells are part of lignocellulosic biomass, they could be valorised via a biorefinery approach in order to extract their diverse constituents. For this reason, the aim of this work was to valorise walnut shells by a biorefinery scheme. The latest involved multiple microwave assisted and conventional hydrothermal treatments for the subsequent valorisation of oligosaccharides. Then, an organosolv delignification of the solid that permitted the maximum oligosaccharide yield was performed, in order to isolate the lignin. Finally, it was treated for cellulose nanocrystal obtaining. The results showed, on the one hand, that the hydrothermal treatments leaded to xyloligossacharide-rich liquors (1–17 g/L). On the other hand, the organosolv delignification resulted into the extraction of a highly pure lignin (93.6%) and a weight average molecular weight of 7000 Da. Moreover, the solid from the delignification treatment was suitable for a successful nanocrystal production. The extracted fractions could be employed in many applications and could be considered renewable precursors for new materials and chemicals. Hence, the proposed biorefinery scheme would allow an integral valorisation of currently undervalued walnut shells.

Synthesis of hierarchically porous ZSM-5 zeolite by self-assembly induced by aging in the absence of seeding-assistance

Microspherical ZSM-5 zeolite possesses a hierarchical porosity with high crystallinity and an adequate surface area was successfully synthesized using the self-assembling method induced by aging in the absence of seeding-assistance, a mesoscale template and organosilanes. The structural properties of the hierarchically porous ZSM-5 zeolite were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis by X-ray (EDAX) thermogravimetric analyzer (TGA), Fourier transform infrared spectrophotometer (FTIR) and nitrogen adsorption/desorption isotherms. The results showed that the formation of microspherical clusters of polycrystalline nanosized ZSM-5 by a conventional hydrothermal treatment at 170 °C in the range of crystallization time 40–72 h from colloidal silica in the absence of seeds. Aging is thought to be the key factor influencing the generation of the hierarchically porous ZSM-5 with a Si/Al ratio of 12.5, surface area of (86.0302 ± 2.1698 m2/g) and pore volume of (0.0684 cm3/g) via the self-assembling method in the absence of seeding-assistance, a mesoscale template and organosilanes. Also, ethanol was an essential element to direct the crystallization toward a favorable product with an outstanding shape and hierarchical porosity. Investigating the order of mixing confirms the importance of adding aluminates precursor to silicates precursor to gain MFI structure.

Comparative study of microwave and conventional hydrothermal treatment of chicken carcasses: Bio-oil yields and properties

This study was conducted to explore the effects of microwave and conventional hydrothermal (MH and CH) treatment on the conversion of chicken carcasses into bio-oil. The differences between MH and CH treatment in terms of bio-oil yields and properties under different reaction temperatures (120–240 °C) were investigated. The bio-oil yield under CH treatment was higher at low temperatures (120–160 °C), whereas that under MH treatment was higher at high temperatures (200–240 °C). The maximum bio-oil yield of 59.41% was obtained by MH treatment at 240 °C. The higher heating values of all bio-oils (34.98–37.22 MJ·kg−1) were significantly higher than that of chicken feedstock (26.46 MJ·kg−1). The bio-oil contained a complex mixture of components that were mainly fatty acids. The bio-oil obtained by MH treatment at 240 °C showed the best flammability and comprehensive combustion performance. The gaseous products in the entire combustion process of bio-oil were mainly CO2 and (C–H)-containing volatiles; additionally, compounds containing H2O, CO, SO2, HCN, CO, and C–O were detected. Compared to bio-oil obtained by CH treatment, that obtained by MH treatment showed a higher calorific value, lower relative content of nitrogen, better flammability, and improved comprehensive combustion performance under the same hydrothermal reaction conditions.

Improvement in the Synthesis Conditions and Studying the Physicochemical Properties of the Zeolite Li-A(BW) Obtained from a Kaolinitic Rock

Crystallization of zeolite Li-A(BW) from kaolinite (Standard Porcelain by the IMERYS Minerals Ltd) through a conventional hydrothermal treatment is here achieved for the first time with no additives as reported in the literature. Moreover lower kaolin calcination temperatures and lower synthesis temperatures are tested and verified in this work. The synthesis process is rather simple as the reaction of kaolinite with alkali occurs very readily after calcination of at 650 °C. Metakaolin is mixed with calculated amount of aluminum hydroxide and lithium hydroxide and the experiment is performed at ambient pressure and 180 ± 0.1 °C. Li-A(BW) is characterized by powder X-ray diffraction, high temperature X-ray diffraction, scanning electron microscopy, inductively coupled plasma optical emission spectrometry, thermal analysis and infrared spectroscopy. Calculation of cell parameters (through Rietveld Refinement) and density, specific surface and pore size are also achieved. The amount of amorphous phase in the synthesis powders is estimated with quantitative phase analysis using the combined Rietveld and reference intensity ratio methods. The results become notably attractive in view of a possible industrial transfer of the synthesis protocol.

A novel approach for the preparation of silver nanoparticles supported on titanate nanotubes and bentonite-application in the synthesis of heterocyclic compound derivatives

The present work aims to study the effect of the type of support on the properties of silver nanoparticles by choosing two kinds of supports with similar characteristics, i.e. titanate nanotubes (TiNT) and Bentonite brought from the northwestern region of Maghnia in Algeria. The titanate nanotubes were prepared by conventional hydrothermal treatment; as for Bentonite, it was first purified, acidified and then doped with silver particles. The Deposition Precipitation with Urea (DPU) method was selected for the preparation of metalized titanate nanotubes (TiNT) as well as Bentonite at 2 wt% of Ag. The prepared materials were characterized by different methods, namely RD/UV–vis, FTIR, BET, XRD, TEM, SEM and EDS. The characterization results showed that titanate nanotubes exhibit a hollow structure with inner and outer diameters generally equal to 3 and 9 nm, respectively. However, silver nanoparticles, with an average size of 2.1 nm, were well distributed over titanate nanotubes and Bentonite. The catalytic activity of the prepared catalysts was investigated by performing the one-pot three-component synthesis of isoxazol-5(4 H)-ones in water, at room temperature. An excellent yield (≈90%) was obtained for the synthesis of isoxazol-5-(4 H)–ones; this yield generally depends on silver content.

Desarrollo de Catalizadores Sólidos tipo Zeolíticos para Valorización de Derivados de Biomasa

El objetivo principal de este plan de tesis es el desarrollo de zeolitas micro/mesoporosas mediante síntesis directa y tratamientos alcalinos post síntesis para su aplicación en procesos catalíticos de valorización de biomasa. En este trabajo se propone la generación de porosidad adicional en zeolitas microporosas con estructura ZSM-5 y ZSM-11 mediante síntesis directa empleando almidón soluble y un surfactante catiónico (CTAB) como plantillas mesoporosas. Se estudió el efecto del tiempo de cristalización y la modificación del contenido de almidón y CTAB en la síntesis sobre la obtención de la estructura cristalina y la generación de mesoporosidad en los materiales. Los sólidos obtenidos fueron caracterizados por diferentes técnicas como difracción de rayos X (DRX), Isotermas de adsorción y desorción de nitrógeno, área superficial BET, Microscopía electrónica de barrido (SEM), Espectroscopía de emisión atómica con plasma inductivamente acoplado (ICP- AES). Los resultados confirmaron que las zeolitas obtenidas por ambas síntesis poseen microporos y mesoporos en su estructura.

Synthesis of silicon-substituted hydroxyapatite using hydrothermal process

An alternative route for preparing silicon-substituted hydroxyapatite powders Ca10(PO4)6−x(SiO4)x(OH)2−x (Si-HAp); using different content of SiO4 (0.588–0.48M) in the aqueous solution of Si precursor was investigated. Tetramethylammonium silicate (TMAS) was used as a silicon precursor. The experiments were carried out via conventional hydrothermal treatments at 150°C for 10h. The Si-HAp nanoparticles obtained were characterized by X-ray diffraction (XRD), Fourier transform IR spectroscopy (FTIR), inductively coupled plasma AES (ICPAES) and scanning electron microscopy (SEM) techniques. A drastically decrease of the diffraction was not observed by increasing the Si content in the structure of the hydrothermally Si-Hap particles produced. A detailed structural analysis conducted by Rietveld refinement indicated that the incorporation of Si occurred in hydroxyapatite (HAp) lattice by partially replacing phosphate (PO43−) groups with silicate (SiO44−) groups. Raman and X-ray photoelectron spectroscopy (XPS) analysis confirmed the substitution of PO43− by SiO44− in the Si-HAp structure. The crystallite size decreases by increasing the Si molar content in the hexagonal HAp structure. TEM observations revealed that the Si-HAp produced have a high crystallinity. A slight decrease of the particle size of the Si-HAp compared to pure HAp was observed (from 60–100nm to 40–70nm). The morphological analysis revealed that all the SiHAp powders prepared have the rod-like shape. Additionally, a slight decrease in both length and diameter of nanorods was observed by increasing the silicon content, the minimum size obtained for the powders containing the largest amount of Si (20Si-HAp) 25 and 70nm. The presence of Si in the structure of the Si-HAp favored densification of the compacts treated at high temperature 1200°C in comparison with pure HAp.