Betaine-modified La-doped ferrihydrite for efficient phosphate removal to ultralow levels.

Commercial Gel-Type Ion Exchange Resin Enables Large-Scale Production of Ultrasmall Nanoparticles for Highly Efficient Water Decontamination

Phosphorus removal from wastewater has been considered as an effective method to control eutrophication and mitigate phosphorus deficiency. Phosphate adsorption using lanthanum-based materials has awakened much attention and triggered extensive research. In this study, novel flower-like LaCO3OH materials were synthesized via a one-step hydrothermal method and evaluated for phosphate removal from wastewater. The adsorbent with flower-like structures prepared at the hydrothermal reaction time of 4.5h (BLC-4.5) exhibited the optimum adsorption performance. BLC-4.5 had a rapid removal rate with more than 80% of the saturated adsorbed phosphate removed within 20min. Furthermore, the maximum phosphate adsorption capacity of BLC-4.5 was as high as 228.5mg/g. Notably, the La leaching amount of BLC-4.5 was negligible in the pH range of 3.0-11.0. BLC-4.5 outperformed most of the reported La-based adsorbents in terms of removal rate, adsorption capacity, and La leaching amount. Moreover, BLC-4.5 had broad pH adaptability (3.0-11.0) and high selectivity for phosphate. BLC-4.5 also displayed excellent phosphate removal efficiency in actual wastewater and great recyclability. The potential adsorption mechanisms of phosphate on BLC-4.5 were precipitation, electrostatic attraction, and inner-sphere complexation via ligand exchange. This study demonstrates that the newly developed flower-like BLC-4.5 reported here is a promising adsorbent for the effective treatment of phosphate in wastewater.

The removal of F-, PO4-3, and SO4-2 from phosphogypsum leachate (pH 1.7) by soil minerals was investigated using a serial batch procedure. PH was the controlling factor in removal of orthophosphate and fluoride, but had less effect on sulfate. Calcium carbonate precipitated major fractions of fluoride and orthophosphate, and smaller amounts of sulfate, during the early stages of leaching; with continued leaching, redissolution of fluoride and orthophosphate occurred, resulting in release of these anions at concentrations exceeding those in the original phosphogypsum leachate. Removal of fluoride and orthophosphate by kaolinite and montmorillonite was strongly affected by pH, due to complex formation, degree of ionization, and charge on the clays. Iron (III) hydroxide had little effect on fluoride or orthophosphate removal due to formation of Ca‐, Al‐, and Fe‐complexes which possibly interfered with adsorption. The iron hydroxide was important to sulfate removal at all pH values; the removal was markedly e...

The removal of both cation and anion contaminants in solution typically requires separate processes or multiple materials, resulting in added complexity and higher operational costs. A cost effective and environmental friendly hybrid adsorbent material has been developed for the removal of Cu(II) and phosphate from the solution. Ferric hydroxide (FHO) was prepared by precipitation methods and then dissolved alginate, a biopolymer, was coated on the surface of the FHO particles to generated FHO-A. In the preparation of FHO-A, the alginate concentration is a critical factor in keeping the FHO-A particles suspended in solution where high concentrations of alginate act as a stabilizer and the FHO-A particles are not settled by gravity. The Cu(II) removal efficiency was wholly dependent on the concentration of alginate via the interaction with the polymer carboxyl groups and was not influenced by the concentration of FHO. Conversely, alginate was not involved in the removal of phosphate and instead, FHO was found to be critical for phosphate removal through electrostatic forces. According to FTIR, the new peaks at 1394 and 1593 cm−1 after coating indicated that the alginate was appended to the surface of the FHO. The shift of peak from 1593 to 1588 cm−1 after Cu(II) adsorption confirms the presence of a Cu-carboxylate interaction. The adsorption of Cu(II) was completed within 5 min, which is very similar to nanoparticle mediated sorption processes. In comparison to Cu(II), the presence of alginate retards the phosphate removal rate. Further, pH dependence was observed in the process, where increasing pH results in increased Cu(II) and decreased phosphate removal rates due to alginate deprotonation and the surface charge effects, respectively. The slowed phosphate sorption rate and shifted peaks in the FTIR spectrum confirmed that the layer of alginate was coated on the FHO particle.

Effects of pH, floc age and organic compounds on the removal of phosphate by pre-polymerized hydrous ferric oxides

Phosphate (P) removal is significant for water pollution control. In this paper, a novel penicillin biochar modified with zirconium (ZMBC) was synthesized and used to adsorb P in water. The results showed that ZMBC had a porous structure and magnetic properties, and the zirconium (Zr) was mainly present in the form of an amorphous oxide. P adsorption displayed strong pH dependence. The Freundlich model described the adsorption process well, and the saturated adsorption capacity was 27.97mg/g (25 ℃, pH = 7). The adsorption kinetics were consistent with the pseudo-second-order model, and the adsorption rates were jointly controlled by the surface adsorption stage and intraparticle diffusion stage. Coexisting anion experiments showed that CO32- inhibited P adsorption, reducing the adsorption capacity by 62.63%. The adsorbed P was easily desorbed by washing with a 1M NaOH solution, and after 5 cycles, the adsorbent had almost the same capacity. The mechanism for P adsorption was inner-sphere complexation and electrostatic adsorption.

Phosphate removal from water using freshly formed Fe–Mn binary oxide: Adsorption behaviors and mechanisms

Activities and mixing functions of the following binary systems at 25° C are discussed: 1. mixtures of tetrahydrofuran with water, methanol, and cyclohexane; 2. mixtures of diethyl ether with water, methanol, and cyclohexane, and 3. mixtures of tetrahydrofuran with diethyl ether. Comparison with similar systems shows that in systems containing methanol, the strongest interactions are formation and breaking of hydrogen bonds between alcohol molecules; interactions between methanol and ether molecules play a minor rǒle. Systems containing water exhibit two main kinds of interaction: formation and breaking of hydrogen bonds between water molecules, and formation of hydrogen bonds between water and ether molecules. Deviations from ideality are larger for diethyl ether than for tetrahydrofuran in water and methanol, and smaller in cyclohexane.

Cooperation of ferrous ions and hydrated ferric oxide for advanced phosphate removal over a wide pH range: Mechanism and kinetics

An Internal Water-Retention Site in the Rhomboid Intramembrane Protease GlpG Ensures Catalytic Efficiency

Interfacial phosphate ions dehydration for advanced phosphate removal and recovery.

Simultaneous organic/inorganic removal from water using a new nanocomposite adsorbent: A case study of p-nitrophenol and phosphate

The application of iron-reducing bacteria (IRB) to phosphate removal from returned liquor (liquid fraction after activated sludge digestion and anaerobic sludge dewatering) of municipal wastewater treatment plant (WWTP) was studied. An enrichment culture and two pure cultures of IRB, Stenotrophomonas maltophilia BK and Brachymonas denitrificans MK identified by 16S rRNA gene sequencing, were produced using returned liquor from a municipal WWTP as carbon and energy source, and iron hydroxide as oxidant. The final concentration of phosphate increased from 70 to 90 mg l(-1) in the control and decreased from 70 to 1 mg l(-1) in the experiment. The mass ratio of removed P to produced Fe(II) was 0.17 g P g(-1) Fe(II). The strain S. maltophilia BK showed the ability to reduce Fe(III) using such xenobiotics as diphenylamine, m-cresol, 2,4-dichlorphenol and p-phenylphenol as sole sources of carbon under anaerobic conditions. Bacterial reduction of ferric hydroxide enhanced the phosphate removal from the returned liquor. The ability of the facultative anaerobes S. maltophilia BK and B. denitrificans MK to reduce Fe(III) was shown. These micro-organisms can be used for anaerobic removal of phosphate and xenobiotics by bacterial reduction of ferric ions.

Removal of oxyanions from synthetic wastewater via carbonation process of calcium hydroxide: Applied and fundamental aspects

This study was performed to determine the ability of wetland bacteriogenic iron oxides (BIOS) to immobilize iodide in contaminated groundwater systems near Chalk River, Canada. The sorption of iodide onto synthetic hydrous ferric oxide (HFO) and BIOS was investigated using an autotitrator and an I− ion-selective electrode to generate high-resolution anion sorption data over a pH range of 2.5 to 9. The effect of strontium sorption in the presence of I− was also investigated to determine its effect on iodide retention as it is also a common contaminant near Chalk River. Both HFO and BIOS correspond to 2-line ferrihydrite with surface areas of 227.7 m2 g−1 and 92.52 m2 g−1, respectively. Sorption of I− was found to be pH dependent for both HFO and BIOS and was most strongly immobilized at pH 2.5. The pH at which 50% of the I− was bound to HFO occurred at pH 4.0, whereas BIOS maintained 50% sorption to pH 9. Field data also indicated a 54% decrease for iodine and 75% for 129I in waters passing over in-situ BIOS at circumneutral pH. Iodide sorption to HFO is best explained by homogeneous functional groups, whereas sorption of I− to BIOS is best explained by heterogeneous functional groups, due to the presence of bacterial functional groups with pKa values that extend to 9.0. The presence of Sr2+ decreased iodide sorption on HFO by 10–20%, but had no effect on BIOS due to its surface functional groups being reactive over the pH range investigated in this study. These results imply that BIOS is a useful sorbent for natural retention of I− from groundwater and that the amount of organic material present in iron oxides is an important factor when considering remediation strategies for radionuclides in groundwater.