Sludge-derived alginate-like extracellular polymers (ALE) for preparation of Fe-ALE and FeCaMg-ALE: Application to the adsorption of phosphate.

Excess phosphorus (P) in wastewater has potential risk of causing harmful algal bloom and eutrophication in receiving wastewater. In this study, alginate-like extracellular polymers (ALE) derived from conventional activated sludge were modified with ionic cross-linking agents (Fe3+, Ca2+, and Mg2+) to develop Fe-ALE and FeCaMg-ALE for the adsorption of phosphate from wastewater. The adsorption process of phosphate by Fe-ALE and FeCaMg-ALE can be well described by pseudo-second-order kinetics and Freundlich isotherm model with a high level of accuracy, indicating that the adsorption processes were chemical, multi-layer adsorption process. The maximum adsorption capacity of dry Fe-ALE and FeCaMg-ALE concerning phosphate were 15.06 and 20.10 mg/g, respectively at 298 K. The adsorption capacity remained relatively consistent across a pH range of 2.0-11.0. FT-IR, XRD, SEM coupled with XPS analysis demonstrated the ALE had been successfully compounded with Fe3+ or Fe3+/Ca2+/Mg2+. Based on the experimental results and characteristic analysis, the main mechanism of phosphate by Fe-ALE and FeCaMg-ALE are physical filling, electrostatic attraction, ligand exchange and precipitation reaction. This work provides a new perspective for preparing ALE-based adsorbent using conventional activated sludge as raw material, realizing the treatment of waste with waste and effectively recovering phosphate from wastewater.

NiCo bimetallic and the corresponding monometallic organic frameworks loaded CMC aerogels for adsorbing Cu2+: Adsorption behavior and mechanism.

In this study, three-dimensional (3D) carboxymethylcellulose sodium (CMC) aerogel was decorated with NiCo bimetallic and the corresponding monometallic organic frameworks to prepare MOFs-CMC composite adsorbents for the removal of Cu2+. The obtained MOFs-CMC composite including Ni/Co-MOF-CMC, Ni-MOF-CMC, and Co-MOF-CMC were characterized by SEM, FT-IR, XRD, XPS analysis, and zeta potential. The adsorption behavior of MOFs-CMC composite for Cu2+ was explored by batch adsorption test, adsorption kinetics and adsorption isotherms. The experimental data satisfied the pseudo-second-order model and Langmuir isotherm model. The maximum adsorption capacities followed the sequence of Ni/Co-MOF-CMC (233.99 mg/g) > Ni-MOF-CMC (216.95 mg/g) > Co-MOF-CMC (214.38 mg/g), indicating that there was a synergistic effect between Ni and Co to promote the adsorption of Cu2+. Combining characterization analysis and density functional theory (DFT) calculation, it is clarified that the adsorption mechanism of MOFs-CMC for Cu2+ includes ion exchange, electrostatic interactions, and complexation.

Preparation of CaMgAl-calcined layered double hydroxides and application on the removal of phosphates.

A calcined CaMgAl-layered double hydroxide nanocomposite, CaMgAl-LDH (CCMA-0.83-600), was prepared by introducing Mg on the basis of CaAl-LDHs for the removal of phosphate from wastewater. The structure of the as-synthesized CCMA-0.83-600 was confirmed by XRD and SEM analyses. Parameters affecting the adsorption process of phosphate adsorbed by CCMA-0.83-600 were thoroughly explored, such as initial pH, adsorbent dosage and co-existing anions. The adsorption kinetic study suggested that the adsorption process accorded with the pseudo-second-order kinetic model and the adsorption rate was controlled by both the liquid film diffusion and intra-particle diffusion. The adsorption isotherm study indicated the adsorption process followed by the Langmuir isotherm model. Thermodynamic analysis suggested that the adsorption of phosphate was spontaneous and exothermic. The obtained results indicated that CCMA-0.83-600 is a suitable candidate for the removal of phosphate from wastewater.

Functional graphene oxide for organic pollutants removal from wastewater: a mini review.

Graphene oxide (GO), an important derivative of graphene, with a variety of active oxygen-containing groups (hydroxyl, carboxyl and epoxy) on its surface is easy to be functionalized to obtain adsorbent with high adsorption capacity. To date, the adsorption behaviour of organic pollutants by functionalized GO adsorbents have been extensively studied, but there has been no systematic review regarding the functionalization method of GO for the purpose to remove organic pollutants from wastewater. The leading objective of this review is to (i) summarize the functionalization strategies of GO for organic pollutants removal (covalent functionalization and non-covalent functionalization), (ii) evaluate the adsorption performance of functional GO towards organic pollutants by taking aromatic pollutants and dyes as examples and (iii) discuss the regeneration property and adsorption mechanism of functional GO adsorbent. In addition, the problems of existing studies and future research directions are also identified briefly.

Preparation of biochar from constructed wetland plant and its adsorption performance towards Cu2.

In order to solve problems in the treatment and disposal of huge production of artificial wetland plants and heavy metal pollution, two constructed wetland plants of reed and gladiolus were selected as raw materials to prepare biochar for adsorbing heavy metals from aqueous solutions. The experimental results showed that reed biochar prepared at 600℃ and activated by KOH with an impregnation ratio of 1:3 (KRAC-3) exhibited relatively high adsorption ability towards Cu2+. The optimal results analyzed by Design-Expert software showed that the maximum adsorption rate of KRAC-3 towards Cu2+ was obtained under the optimal conditions of adsorbent dosage of 1.2 g/L, pH of 4.96, and reaction time of 137.43 min. The adsorption of Cu2+ followed pseudo-second-order kinetics and the Langmuir adsorption model. The theoretical maximum adsorption capacity of KRAC-3 calculated from the Langmuir isotherm model was 148.08 mg/g. Microscopic tests with the help of SEM, EDS, and XRD revealed that physical adsorption, ion exchange, electrostatic adsorption, surface complexation, and precipitation were the main adsorption mechanism of Cu2+ loading onto KRAC-3. This study will provide a theoretical basis for the application of biochar prepared from constructed wetland plants and the treatment of heavy metal-containing wastewater.

From wastes to functions: preparation of layered double hydroxides from industrial waste and its removal performance towards phosphates.

To control eutrophication and recover phosphate from wastewater, a calcium carbide slag and red mud composite material (CR-LDH) was prepared using industrial waste as raw material for phosphorus adsorption. The morphology and structure of synthesized CR-LDH were characterized by FT-IR, SEM, EDS, and XRD measurements. Bath adsorption test results showed that the optimal dosages of adsorbent and pH for phosphate were 5 g·L-1 and pH of 7, respectively. The experimental data could be well described by pseudo-second-order kinetic and Langmuir isotherm models, suggesting that the adsorption process of CR-LDH with respect to phosphate was a chemical and monolayer process. The theoretical maximum adsorption capacity obtained by Langmuir isotherm model was 16.06 mg·g-1 at 25 °C. The intra-particle diffusion model fitting results indicated that the adsorption of phosphate by CR-LDH was controlled by both liquid membrane diffusion and intra-particle diffusion. Phosphate was bound to CR-LDH via synergistic effect of physical adsorption, ion exchange, anion intercalation, and chemical precipitation as evidenced from a combination of microscopic analysis and adsorption mechanism study. The actual phosphate-containing wastewater investigation showed that CR-LDH not only exhibited good removal effect on phosphate, but also could greatly reduce turbidity, COD, and ammonia nitrogen, which was suitable for disposal of practical wastewater. The COD, turbidity, and NH4+-N could be reduced by 42.39%, 77.20%, and 20.71%, respectively. These results indicate that CR-LDH can be considered as potential adsorbent for the treatment of phosphate-containing wastewater, which will be helpful to achieve the goal of "treating waste with waste and turning waste into treasure".

In situ fabrication of I-doped Bi2O2CO3/g-C3N4 heterojunctions for enhanced photodegradation activity under visible light.

Iodine-doped Bi2O2CO3/g-C3N4 heterojunctions consisting of graphitic carbon nitride (g-C3N4) and iodine-doped bismutite (Bi2O2CO3) components were successfully in situ synthesized by a one-pot hydrothermal method. Characterizations such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) demonstrated iodine was favorably doped into the Bi2O2CO3 component, of which the {001} facets grew in situ from {002} facets of g-C3N4 for the heterostructure construction of I-doped Bi2O2CO3/g-C3N4 (IB/CN). The photocatalytic activity of catalysts was evaluated by the degradation efficiency of 1,5-dihydroxynaphthalene under visible light. 1.5-IB/CN with a reasonable iodine doping amount (Bi: I molar ratio = 1.0: 1.5) exhibited the superior photodegradation performance compared to Bi2O2CO3, achieving an 85.5% removal ratio after 100 min illumination. The enhanced activity of 1.5-IB/CN was attributed to both of the heterostructure that promoted the separation of photoinduced carriers and iodine doping that tuned the bandgap for sufficient visible-light harvesting. The degradation intermediates of 1,5-dihydroxynaphthalene in the system were determined and its possible photodegradation pathway was proposed in detail. This study provides a rational approach for enhancing the visible-light catalytic activity of wide-bandgap Bi2O2CO3, and reveals a new perspective on the removal mechanism of organic pollutants.

A comparative study of Lonicera japonica with related species: Morphological characteristics, ITS sequences and active compounds.

Morphological characteristics, ITS sequences, and active compounds have been used to differentiate between species of Lonicera used in the traditional Chinese medicines Flos Lonicerae Japonicae (FLJ) and Flos Lonicerae (FL). FLJ includes L. japonica whereas FJ includes Lonicera macranthoides, Lonicera hypoglauca, Lonicera confusa and Lonicera fulvotomentosa. FLJ could be distinguished from FL using four quantitative and 10 qualitative characters, ITS sequences, chlorogenic acid and luteoloside contents. Analyses revealed that L. japonica was very different from the other species. The results have implications for the identification and quality control of species of Lonicera used medicinally, suggesting that species should not be interchanged in medicinal preparations.

[Study on chemical diversity of volatile oils in Houttuynia cordata and their genetic basis].

OBJECTIVE: To reveal chemical diversify of volatile oils in Houttuynia cordata from major producing areas in China and their genetic basis, lay a foundation for breeding a quality H. cordata variety. METHOD: The volatile oils in H. cordata from 22 provenances were determined by GC. And the relationship among the peak areas of volatile oils, biological characteristics and RAPD makers were analyzed. RESULT: There were common and special volatile oils in H. cordata from different provenances. The peak areas of common volatile oils in samples were significantly different. The clustering figure based on the peak areas or the relative peak areas of common volatile oils was almost agreed with the one based on RAPD makers analysis. And the differences in chromatograms could be distinguished according to the biological characteristics. CONCLUSION: The diversity of volatile oils exists in H. cordata from different provenances which relate with biological characteristics and has genetic basis. H. cordata can be divided into 2 types according to volatile oils, biological characteristics or RAPD marker.