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Seeking high performance adsorbents for highly efficient treatment of wastewater containing organic dyes has become increasingly imperative worldwide. Herein, with a specific surface area (SSA) of 2,745.4 m2·g−1, trace N-doped porous biochar nanospheres (NPBs) are derived for the first time from affluent waste corn roots, via a hydrothermal conversion followed by a mild calcined activation by K2CO3 (KC) in the presence of low virulent melamine. Melamine acts as N source and synergistic activator for significant promotion in SSA, pore volume, and surface defects. The obtained NPBs (CHC-0.5N-4KC-900) are confirmed as superior adsorbents for removal of organic dyes rhodamine B (RhB, qm = 1,630.7 mg·g−1) and Congo red (CR, qm = 1,766.2 mg·g−1) as well as their mixtures, within not only a low (< 50 mg·L−1) but also a high (> 50, esp. 250–1500 mg·L−1) concentration range. The values for qm are far beyond commercially activated carbon (AC) as well as most reported biomass derived carbons, undoubtedly revealing the NPBs as great promising candidate adsorbents for disposal of real industrial wastewater. In addition, the adsorption of RhB is fitted by Langmuir, Freundlich, Temkin, and Dubinin—Radushkevich isotherm models. The kinetic analysis indicates that the adsorption before equilibrium conforms to the pseudo-second-order model, and the hydrogen bonding, electrostatic attraction, and esp. π−π interaction have contributed to the superior adsorption performance of the NPBs. [ABSTRACT FROM AUTHOR]

Heavy metal ions have attracted considerable concern for their high toxicity and potential malign effects on the water environment, and adsorption has been regarded as one of the most versatile and effective techniques towards water treatment. In view of this, hierarchical porous carnation-like Ca4B10O19·7H2O microspheres self-assembled by two-dimensional (2D) quasi-hexagonal nanoplates are successfully synthesized for the first time as far as we know, by a facile and surfactant ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) assisted hydrothermal approach using CaCl2·2H2O, NaOH and H3BO3 as the raw materials. The as-obtained carnation-like Ca4B10O19·7H2O microspheres exhibit a uniform morphology, ca. 89% of which have a diameter within the range of 8.0–11.0 μm. A probable EDTA-2Na assisted self-assembly formation mechanism has also been proposed based on systematic control experiments. Meanwhile, the carnation-like Ca4B10O19·7H2O microspheres demonstrate a transparent characteristic from the ultraviolet to the visible region, a hierarchical porous structure (specific surface area: 32.79 m2 g−1, pore volume: 0.151 cm3 g−1, average pore diameter: 3.704 nm) and satisfactory thermal stability. In addition, the carnation-like microspheres are confirmed as great satisfactory adsorbents for heavy metal ion (Pb2+) removal with an adsorption capacity qm of 256.4 mg g−1, which may also be employed as excellent adsorbent candidates for other heavy metal or organic dye removal in water treatment as well as catalyst carriers in heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

One-dimensional (1D) nanostructured metal borates have drawn considerable attention owing to their versatile applications in a multitude of fields, but it is still a great challenge to achieve a high aspect ratio in these materials via a facile and feasible route. Herein, ultralong Ca2B2O5·H2O nanowires with a length of 110–230 μm and ultrahigh aspect ratio of 240–750 are successfully synthesized for the first time via a facile water-bath pretreated eco-friendly hydrothermal technique in the absence of any additives, using low cost CaCl2, H3BO3 and NaOH as the raw materials. The formation mechanism of the ultralong nanowires is studied in detail by varying the process parameters (water-bath and hydrothermal temperature, duration time, etc.). The water-bath treatment plays a key role in the formation of thin hexagonal Ca(OH)2 nanoplates, favoring subsequent conversion to ultralong nanowires with a high aspect ratio. The as-obtained Ca2B2O5·H2O:5.0%RE3+ (rare earth, RE = Eu, Tb) nanophosphors exhibit strong photoluminescence emission and excitation performance, with corresponding Commission Internationale de l'Eclairage (CIE) values determined as (0.635, 0.364) and (0.320, 0.597) within the red and green regions, respectively. This not only suggests that the ultralong Ca2B2O5·H2O nanowires are promising structure- and function-integrated photoluminescent host candidates, but also provides a novel and facile route for the formation of high aspect ratio 1D nanostructures of other metal borates. [ABSTRACT FROM AUTHOR]

Nickel phyllosilicates have attracted much attention owing to their potential applications in various fields. Herein, Ni3Si4O10(OH)2 porous microspheres (NiSi-PMs) with a diameter of 1.2 to 3.2 μm were successfully fabricated via a urea-assisted hydrothermal method, and subsequently used to prepare supported Pd catalyst. Characterizations of the NiSi-PMs and the obtained catalyst, combined with the catalytic performance for the hydrogenation reaction, are presented and discussed. The BET surface area and pore volume of the NiSi-PMs were 196.2 m2 g−1 and 0.70 cm3 g−1, respectively. The Pd/NiSi-PMs catalyst exhibited remarkable catalytic activity for the hydrogenation of styrene under mild conditions, with a turnover frequency of 5234 h−1, and the catalyst was recovered and recycled for six consecutive cycles without any discernible loss of activity. H2-TPR and H2-TPD revealed that the activity of the catalysts was closely related to the adsorption property for hydrogen. The present Ni3Si4O10(OH)2 supported Pd catalyst afforded a promising and competitive candidate for heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Calcium silicate 1D nanostructures have aroused widespread concern and become widely available for drug delivery, and photoluminescence host, etc. , which however have traditionally been synthesized via high temperature based molten salt synthesis or solution-based techniques, in the presence of organic template or solvents. Herein, a facile controllable green hydrothermal route (200 °C, 12.0 h) to uniform high aspect ratio high purity Ca 6 Si 6 O 17 (OH) 2 nanowires (diameter: 20.0–120.0 nm, aspect ratio: 60.0–350.0) has been developed for the first time by using abundant CaCl 2 ·2H 2 O and Na 2 SiO 3 ·9H 2 O as raw materials, in the absence of any organic stabilizer, template, or directing agent. Effects of process parameters such as molar ratio of reactants, reaction time, temperature, reactant concentration, and dropping rate on the hydrothermal products were investigated in detail, and an intrinsic highly anisotropic structure induced hydrothermal formation mechanism of the high aspect ratio Ca 6 Si 6 O 17 (OH) 2 nanowires was proposed. The Ca 6 Si 6 O 17 (OH) 2 nanowires exhibited a transparent characteristic from the ultraviolet to visible range, and the Ca 6 Si 6 O 17 (OH) 2 :1.2%Tb 3+ nanophosphors demonstrated the strongest photoluminescence emission intensity. With the doping molar percentage of Tb 3+ changing from 0.5% to 1.5%, the quantum yields (QYs) varied within the range of 43%–72%, definitely suggesting the Ca 6 Si 6 O 17 (OH) 2 nanowires as a great promising host candidate for green-emitting luminescent materials in light display systems, and optoelectronic devices, etc. [ABSTRACT FROM AUTHOR]

Water pollution has become one of the most urgent environmental issues to be solved for the global society, how to rapidly and efficiently dispose of dye such as RhB-contaminated effluents has become an imperative issue from an environmental point of view. In this contribution, uniform mesoporous Mg 3 Si 2 O 5 (OH) 4 microspheres (88.0% of which have a diameter of 1.22–1.78 μm, S BET = 281.68 m 2 g −1 ) consisted of nanosheets have been synthesized via a facile H 3 BO 3 assisted cost-effective eco-friendly hydrothermal process (180 °C, 12.0 h), using abundant SiO 2 , MgCl 2 ·6H 2 O, and NaOH as the raw materials. Based on the effects of process parameters, the H 3 BO 3 assisted SiO 2 template-formation mechanism is investigated in detail, and especially the key role of H 3 BO 3 as the inorganic director/quasi surfactant is illustrated. When employed as the adsorbents for removal of RhB, the adsorption isotherm is well described by the Langmuir adsorption model, with the maximum monolayer adsorption capacities of 300.08 mg g −1 (higher than most of the referenced adsorbents). Meanwhile, the intra-particle diffusion model also well fits to the kinetic data, suggesting the diffusion within the mesopores of the rate-limiting step. Moreover, the recycling performance reveals the as-obtained mesoporous microspheres as highly efficient adsorbents for removal of RhB with satisfactory chemical, morphological and structural stability. [ABSTRACT FROM AUTHOR]

Towards the malignant impact of red mud on the environment and water pollution caused by organic dyes, affluent residual iron ions in red mud are recovered and converted into functional hierarchical porous α-Fe 2 O 3 microspheres (HP α-Fe 2 O 3 MSs) comprising nanosheets (S BET : 78.75 m2 g−1, pore volume: 0.35 cm3 g−1, mean pore diameter: 15.92 nm) via a facile hydrothermal route (180 °C, 12.0 h), with the presence of urea and CTAB. When employed as the adsorbents for Congo red (CR) in simulated wastewater, the adsorption isotherm is well fitted with Langmuir isotherm model, and the corresponding maximum adsorption capacity is determined as 342.57 mg g−1, superior to that of most referred adsorbents in literatures. Meanwhile, the adsorption kinetic data can be well interpretated via the pseudo-second-order and intra-particle diffusion models. Moreover, the red mud derived HP α-Fe 2 O 3 MSs can be easily regenerated and reused with satisfactory chemical, morphological and structural stability. Affluent residual iron in red mud is extracted for the facile green hydrothermal synthesis of the hierarchical porous α-Fe 2 O 3 microspheres as efficient adsorbents for removal of Congo red, with excellent adsorption capacity and satisfactory recycling performance. Image 1 • Abundant iron in red mud is hydrothermally converted into hierarchical porous α-Fe 2 O 3 microspheres. • Adsorption isotherm can be well fitted with Langmuir isotherm model, with the q m determined as 342.57 mg g−1. • Microspheres can be easily regenerated and reused with satisfactory chemical, morphological and structural stability. • Major phase of the quasi amorphous iron-bearing room temperature precipitate is determined as Fe(OH) 3. • Adsorption kinetic data can be well interpretated via the pseudo-second-order and intra-particle diffusion models. [ABSTRACT FROM AUTHOR]

• A facile green rotating hydrothermal process is developed for quasi waxberry-like Ba 5 Si 8 O 21 microspheres. • Ba 5 Si 8 O 21 microspheres are formed at lower temperature with miniaturization of size in the absence of any surfactants. • A probable heat and mass transport enhanced rotating hydrothermal formation mechanism is proposed. • The microspheres exhibit high adsorption performance for CR (q m : 1238.7 mg g−1) with satisfactory stability and reusability. • The adsorption mechanism is systematically and deeply investigated. Towards the imperative water contamination by organic dyes, uniform hierarchical quasi waxberry-like Ba 5 Si 8 O 21 microspheres (diameter: 0.65–1.30 µm) consisted of nanorods have been successfully synthesized via a facile eco-friendly and cost-effective rotating hydrothermal process (120 °C, 6.0 h) without any organic additives, templates or surfactants, using abundant BaCl 2 ·2H 2 O and Na 2 SiO 3 ·9H 2 O as the raw materials. Based on the impacts of the process parameters, a probable heat and mass transport enhanced rotating hydrothermal formation mechanism is proposed. The rotating homogeneous hydrothermal reactor provides vigorous macro- and micro-mixing of the solid and solution phase, thus favors the early stage dissolution-recrystallization, formation of the product nuclei at lower temperature, and final self-assembly for uniform waxberry-like microspheres with miniaturization of size. When employed as the adsorbents for the elimination of Congo red (CR) from simulated waste water, the adsorption data are well fitted with Langmuir isothermal model (q m : 1238.7 mg g−1). Meanwhile, the adsorption of CR is well described by the pseudo-second-order kinetic and intra-particle diffusion models, indicating the final diffusion at equilibrium stage within the mesopores of the real rate-limiting step in the whole adsorption process. The recycling test further confirms the Ba 5 Si 8 O 21 microspheres as highly efficient adsorbents with satisfactory stability and reusability. As a noteworthy methodology, the heat and mass transport enhanced rotating hydrothermal synthesis presents new insights into the hierarchical porous silicate microspheres as a competitive candidate adsorbent for organic dyes removal, and also a potential new platform for heterogeneous catalysis. [ABSTRACT FROM AUTHOR]