Lanthanum-calcium bimetallic-modified attapulgite- chitosan hydrogel beads for efficient phosphate removal from water: Performance evaluation, mechanistic and life cycle assessment.

Phosphorus is a critical factor in the control of eutrophication. We developed a three-dimensional porous, bimetallic-modified adsorbent La-Ca-CS/ATP to remove excess phosphate from water. Langmuir model showed that the theoretical adsorption capacity of La-Ca-CS/ATP was up to 123 mg P/g. The amount of La and Ca leached by La-Ca-CS/ATP was small, and the adsorption of 36.08 mg P/g was maintained during the five cycles of La-Ca-CS/ATP. The La-Ca-CS/ATP adsorption mechanism mainly involved surface precipitation, ligand exchange, electrostatic attraction, and inner-sphere complexation. Molecular dynamics demonstrated that La and Ca had complementary effects on binding sites and energy barriers within the range of 0.5-0.7 nm and 1.2-2 nm, enhancing the adsorption effect of La-Ca-CS/ATP. The life cycle assessment results showed that adding calcium could help reduce the environmental impact of lanthanum and chitosan. The production of La-Ca-CS/ATP adsorbed 73.88 P mg/g and emitted 24.73 kg CO2 eq, which was less than other adsorbents.

Lanthanum modified chitosan-attapulgite composite for phosphate removal from water: Performance, mechanisms and applicability.

A novel lanthanum-modified-chitosan-attapulgite (La-CTS-ATP) composite with efficient adsorption of phosphate in water was prepared and characterized. The adsorption properties were investigated by adsorption kinetics, adsorption isotherms and thermodynamics. An orthogonal design test was used to explore the optimal preparation conditions of La-CTS-ATP. Various characterizations exhibited the successful modification of lanthanum and the effective adsorption of phosphate. The batch experiments showed that La-CTS-ATP exhibited excellent stability within pH range of 4-10 and the disturbance of co-existing substances (Cl-, NO3-, HCO3-, SO42-). Chemisorption played the main role in phosphate adsorption from kinetic studies. Isotherm studies illustrated monolayer uptake of adsorbents onto the adsorbent, and the maximum adsorption capacity was 102.90 mg/g, much higher than other La-based adsorbents. The reaction process was spontaneous (ΔG < 0), exothermic (ΔH < 0) and disordered (ΔS > 0) from thermodynamic analysis. The excellent reusability of La-CTS-ATP was investigated, after five cycles, the phosphate removal rate and desorption rates were 72.93 % and 77.44 %, respectively. The dynamic adsorption experiments showed that the faster the flow rate, the shorter the time for La-CTS-ATP to get saturation, and the maximum adsorption capacity was slightly reduced. The surface precipitation, electrostatic attraction, and ligand exchange were the main mechanisms affecting its adsorption behavior. The adsorbent exhibited excellent effectiveness in real wastewater (breeding wastewater and domestic wastewater). In this study, a novel and effective adsorbent for phosphorus removal was produced in contaminated water, and the analysis of the adsorption process of the system provides new insights for related research.

Syntheses of tetrahydroquinoline-based chiral carbene precursors and the related chiral NHC-Au(i) complex.

Four tetrahydroquinoline-based chiral carbene precursors were synthesized using unsymmetrical N,N'-diarylformamidines and chiral 2-allyloxiranes as starting materials. A representative NHC-gold complex has been prepared and fully characterized, the crystal structure of which reveals an intramolecular Au⋯H-C(sp3) interaction between Au(i) and the hydrogen atom of the isopropyl moiety in the N-aryl group.

NIS/PhI(OAc)2-mediated diamination/oxidation of N-alkenyl formamidines: facile synthesis of fused tricyclic ureas.

Facile synthesis of bicyclic ureas by NIS/PhI(OAc)2-mediated diamination/oxidation of N-alkenyl formamidines is reported. Bulky aromatic groups such as 2,6-diisopropylphenyl and mesityl and alkyl groups were tolerated towards the process. Several control experiments have been performed, and the reaction outcomes indicate that the oxidation process is probably concerted with the diamination cyclization, and succinimide generated from NIS-mediated aminoamidiniumation step promoted the PhI(OAc)2-mediated oxidation step. The new methodology provides an efficient method for the synthesis of fused tricyclic ureas.

Metal-free aminoamidiniumation employing N-iodosuccinimide: facile syntheses of bicyclic imidazolidiniums and cyclic vicinal diamines.

NIS-mediated aminoamidiniumation has been developed for the syntheses of bicyclic imidazolidinium salts, which could be readily converted into cyclic vicinal diamines.