Recovering rare earth elements via immobilized red algae from ammonium-rich wastewater.

Biotreatment of acidic rare earth mining wastewater via acidophilic living organisms is a promising approach owing to their high tolerance to high concentrations of rare earth elements (REEs); however, simultaneous removal of both REEs and ammonium is generally hindered since most acidophilic organisms are positively charged. Accordingly, immobilization of acidophilic Galdieria sulphuraria (G. sulphuraria) by calcium alginate to improve its affinity to positively charged REEs has been used for simultaneous bioremoval of REEs and ammonium. The results indicate that 97.19%, 96.19%, and 98.87% of La, Y, and Sm, respectively, are removed by G. sulphuraria beads (GS-BDs). The adsorption of REEs by calcium alginate beads (BDs) and GS-BDs is well fitted by both pseudo first-order (PFO) and pseudo second-order (PSO) kinetic models, implying that adsorption of REEs involves both physical adsorption caused by affinity of functional groups such as -COO- and -OH and chemical adsorption based on ion exchange of Ca2+ with REEs. Notably, GS-BDs exhibit high tolerance to La, Y, and Sm with maximum removal efficiencies of 97.9%, 96.6%, and 99.1%, respectively. Furthermore, the ammonium removal efficiency of GS-BDs is higher than that of free G. sulphuraria cells at an initial ammonium concentration of 100 mg L-1, while the efficiency decreases when initial concentration of ammonium is higher than 150 mg L-1. Last, small size of GS-BDs favors ammonium removal because of their lower mass transfer resistance. This study achieves simultaneous removal of REEs and ammonium from acidic mining drainage, providing a potential strategy for biotreatment of REE tailing wastewater.

Morphology library of nanosilica based on a thermally induced deformable template.

We report a versatile platform for the synthesis of shape-tunable nanosilica based on a thermally induced deformable template with diverse morphologies ranging from spheres, horns, ultrathin nanosheets, and rings to belts. This was realized by creating soft templates from a pair of anionic/cationic surfactants.

Biobased Plasticizers from Tartaric Acid: Synthesis and Effect of Alkyl Chain Length on the Properties of Poly(vinyl chloride).

A series of tartaric acid (TA) esters with different side chain lengths [dibutyl TA esters (DBTAE)-Cn], as plasticizers for poly(vinyl chloride) (PVC), is herein reported. Their structures have been fully characterized using proton nuclear magnetic resonance and Fourier-transform infrared spectroscopy. Their compatibility and plasticizing effect for soft PVC were evaluated using thermogravimetric analysis, dynamic mechanical analysis, tensile testing, and migration testing. The results showed that all these TA esters exhibit good plasticizing performance. At a concentration of 30 phr in PVC, the best results for the plasticizing effect, in terms of glass transition temperature reduction and elongation at break, were achieved when the ester DBTAE-C4 was used. However, the longer side chains of these esters improved the thermal stability of soft PVC blends yet exacerbated the migration behavior of these esters from PVC films in n-hexane. The properties of the plasticized PVC blends depended on the structural features of DBTAE-Cn. The plasticizing performances of the esters DBTAE-C1 and DBTAE-C4 rivaled that of dioctyl phthalate (DOP), suggesting that they have the potential to replace DOP in soft PVC materials.

Keggin-type Heteropolyacids-Catalyzed Selective Hydrothermal Oxidation of Microalgae for Low Nitrogen Biofuel Production.

Hydrothermal liquefaction (HTL) of microalgae for biofuel production is suffering from low bio-oil yield and high heteroatomic compositions owing to their low efficiency and selectivity to hydrolysis of cellular compounds. Hereby we report Keggin-type (Mo-V-P) heteropolyacids (HPAs)-catalyzed HTL of microalgae for efficient low-nitrogen biocrude production. The increases of reaction temperature, reaction time, and vanadium substitution degrees of HPAs are favorable to biocrude yield initially, whereas a significant decrease of biocrude yield is observed owing to the enhanced oxidation of carbohydrates above the optimum reaction conditions. The maximum biocrude yield of HPAs-catalyzed HTL of microalgae is 29.95 % at reaction temperature of 300 °C, reaction time of 2 h, and 5 wt% of HPA-4, which is about 19.66 % higher than that of control with 71.17 % less N-containing compounds, including 1,3-propanediamine, 1-pentanamine, and 2, 2'-heptamethylene-di-2-imidazoline than that of control. This work reveals that HPAs with Brønsted acidity and reversible redox properties are capable of both enhancing biocrude production via catalyzing the hydrolysis of cellular compounds and reducing their nitrogen content through avoiding the Maillard reactions between the intermediates of hydrolysis of carbohydrates and proteins. HPAs-catalyzed HTL is an efficient strategy to produce low N-containing biofuels, possibly paving the way of their direct use in modern motors.

Nano-Hydroxyapatite Particle Brushes via Direct Initiator Tethering and Surface-Initiated Atom Transfer Radical Polymerization for Dual Responsive Pickering Emulsion.

Well-defined polymer-grafted solid inorganic nanoparticles (NPs) are imperative for practical applications in various fields based on the prerequisite of facile initiator immobilization. Direct atom transfer radical polymerization (ATRP) initiator-tethered solid NPs are described using 2-bromo-2-methylpropionic acid as a tetherable initiator. To illustrate the versatility of the proposed strategy, nano-hydroxyapatite (n-HAP) nanocrystals (NCs) were selected to demonstrate the morphology-controlled synthesis of 2-bromo-2-methylpropionate (2-BrMP) group-immobilized n-HAP (n-HAP-Br) NCs. When water was employed as the sole solvent, the continually introduced 2-BrMP groups altered the surface hydrophobic capacity of the n-HAP-Br NC and thus led to unavoidable aggregation of n-HAP-Br NCs. The synthesis of individually dispersed n-HAP-Br NCs was achieved by rational adjusting polarity of the aqueous medium through adding a portion of water-miscible organic solvents. The type and concentration of added water-miscible organic solvents had critical effects on the morphology and particle size of n-HAP-Br NCs. To verify the efficiency of the tethered initiator, n-HAP-g-poly2-(dimethylamino) ethyl methacrylate (n-HAP-g-PDMAEMA), n-HAP-g-polyacrylonitrile (n-HAP-g-PAN), and n-HAP-g-polymethyl methacrylate (n-HAP-g-PMMA) were fabricated by surface-initiated ATRP (SI-ATRP). Acting as a solid particle emulsifier, the designed n-HAP-g-PDMAEMA-stabilized Pickering emulsion displayed dual pH and temperature response with reversible behaviors. This work presents a versatile and simple way for the fabrication of initiator-immobilized solid NPs (e.g., n-HAP NCs, gibbsite nanoplatelets, and γ-FeOOH nanofibers) ready for polymer grafting and thus enables promising performance in widespread applications.

Unexpectedly High Adsorption Capacity of Esterified Hydroxyapatite for Heavy Metal Removal.

Nanohydroxyapatite (n-HAP) as an environmentally friendly adsorbent of heavy metal ions still requires the rational design of the pore structure and surface characteristic for enhancing their adsorption capacity toward heavy metal ions. A novel one-step strategy was developed to regulate the pore structure and surface characteristic of esterified HAP (n-EHAP) nanocrystals (NCs) for enhancing the adsorption capacity by incorporation of 2-bromo-2-methylpropionate (2-BrMP) groups on the surface of n-EHAP NCs. When using water as the sole solvent, the aggregation of n-EHAP NCs became unavoidable because of incorporation of hydrophobic 2-BrMP groups on n-HAP particle surfaces. The synthesis of uniform and individual n-EHAP NCs was achieved by rational adjustment of the aqueous dispersion medium to avoid agglomeration and precipitation, which was induced by the changing surface characteristic of n-EHAP NCs during the continuing incorporation of hydrophobic 2-BrMP groups in the water/acetone system. The successful incorporation of hydrophobic 2-BrMP groups on the surface of n-EHAP NCs was characterized by X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and liquid nitrogen adsorption isotherms. To explore the potential application in water treatment, a series of systematically designed batch experiments were conducted to determine the influences of the adsorbent dosage, solution pH, and contact time on the adsorption behavior of n-EHAP NCs. Experimental results indicated that the addition of water-soluble acetone greatly promoted the formation of individual n-EHAP NCs without aggregation, and furthermore, the successful incorporation of hydrophobic 2-BrMP groups led to formation of porously structured n-EHAP NCs with a higher surface area and an increasing micro-/mesopore ratio. Compared with pristine n-HAP, n-EHAP NCs exhibited lower crystallinity with smaller crystallite size and demonstrated an ultrahigh adsorption capacity for Pb(II) in acidic solution with a record of close to 2400 mg/g. The improved performance of n-EHAP NCs originated from both the suitable porous structure with a higher micro-/mesoporosity ratio and the existing tethered 2-BrMP group-induced the ester bond, providing more adsorption active affinity sites for heavy metal ions. The highly efficient adsorption (99.99%) was further achieved using tap water spiked with traces of Pb(II) (63 ppb). The presented findings promise the application of n-EHAP NCs in water treatment as an alternative, low-cost, and ecofriendly adsorbent for environmental remediation.

Treatment of high-nitrate wastewater mixtures from MnO2 industry by Chlorella vulgaris.

The aim of this work was to study the biotreatment of mixed wastewaters collected from two points of MnO2 industry by Chlorella vulgaris. Their growth rates in four mixed wastewaters with mass ratio of wastewater 1#:2# of 20:1, 50:1, 100:1, and 200:1 were characterized, and the lag phase was shortened with increase of nitrate concentrations. The N, P, and metal removal kinetics were quantified each other day to evaluate the bio-treatment efficiencies of high-nitrate wastewaters from MnO2 industry. 84.68% and 98% of N, P has been removed. The Ca, Zn, Mn, and Si in mixed wastewaters was removed with maximum removal efficiencies of 97.91%, 99.37%, 99.44%, and 81.68%, respectively. The compositions of Chlorella vulgaris cultured in mixed wastewaters, including proteins, lipids, ash contents, and carbohydrates, were investigated in detail. The optimum HHV of Chlorella vulgaris about 18 MJ/Kg presented a potential to decrease the cost of algal biofuel.