Facile surface modification of mesoporous silica with heterocyclic silanes for efficiently removing arsenic

Modulating Fe sites by La in porous MnFe2O4 for enhanced removal of ROX: Synergy of efficient adsorption and PMS activation

Catalytic-adsorption method is a promising strategy for degrading organoarsenic compounds and removing secondary inorganic arsenic. The method relies significantly on heterogeneous catalysts with selectively adsorption and enhanced peroxymonosulfate (PMS) activation capacity. In this study, active sites for selective adsorption and PMS activations were developed by modulating the Fe-sites in porous MnFe2O4 through La-doping. Synchrotron radiation, EPR, and XPS characterizations confirmed the presence of oxygen vacancies, metal hydroxyl groups M(Fe/Mn/La)-(OH) and the active Fe(II)/Mn(II,III), as well as the fine structure of La occupied sites. Theoretical calculations indicate that the generation of Vo would increase the local electron cloud density of La dopants, leading to the transfer of local electrons into the bulk phase. The electron transfer characteristics result in the raising the d-band center of MnFe2O4 and lowering the Gibbs free energy of the intermediate state, thus promoting 1O2 generation. In 3% La-MnFe2O4/PMS system, 96% ROX (10 mg/L) were removed within 35 min with the secondary inorganic arsenic levels below 10 μg/L. The rate coefficients k for ROX removal in porous 3%La-MnFe2O4/PMS is 4.05 times higher than that in MnFe2O4/PMS. ROX was effectively removed in different water matrices (Liao River, Hun River, and groundwater), demonstrating the practical application potential of 3%La-MnFe2O4/PMS system. Under continuous flow conditions, the average of 97.9% and 87.3% of ROX were removed from ultrapure water and groundwater, respectively, over a 10-hour continuous run. This study highlights the high-performance spinel La-MnFe2O4 for the synergistic enhancement of PMS activation, secondary arsenic adsorption, and improved mass transfer, contributing to green and safe water treatment strategies.

Aminoalkyl-organo-silane treated sand for the adsorptive removal of arsenic from the groundwater: Immobilizing the mobilized geogenic contaminants

Arsenic (As), a geogenic legacy pollutant can be present in environmental matrices (water, soil, plants, or animal) in two redox states (As(III) or As(V)). In the present study, charged mono- and di-amino functionalized triethoxy and methoxyorganosilane (TT1 and TT2- 1% and 5%) were impregnated with quartz sand particles for the treatment of As polluted water. Spectroscopic characterization of organosilane treated sand (STS) indicated the co-existence of minerals (Mg, Mn, Ti), amide, and amidoalkyl groups, which implies the suitability of silanized materials as a metal(loids) immobilization agent from water. Changes in peaks were observed after As sorption in Fourier thermal infrared and EDS images indicating the involvement of chemisorption. Batch sorption studies were performed with the optimized experimental parameters, where an increased removal (>20% for TT2-1% and >60% for TT1-1%) of As was observed with sorbate concentration (50 µg L^-1), temp. (25 ± 2 ºC) and sorbent dosages (of 10 g L^-1) at 120 min contact time. Among the different adsorbent dosages, 10 g L^-1 of both TT1 and TT2 was selected as an optimum dosage (maximum adsorption capacity ≈ 2.91 μg g^-1). The sorption model parameters suggested the possibility of chemisorption, charge/ion-dipole interaction for the removal of arsenate.

Synthesis, Crystal Structure, and Insecticidal Activity of Steroidal N-Piperidone

A series of steroidal piperidone derivatives were synthesized, and their agricultural activities were evaluated against Myzus persicae, Aphis citricola, Brevicoryne brassicae Linn., and Bemisia tabaci (Gennadius). Most of the tested compounds exhibited potent insecticidal activity against these four pests. Compound I-9 displayed the highest activity against M. persicae, A. citricola, and Brevicoryne brassicae, with LC₅₀ values of 11.3, 10.4, and 8.68 μg/mL, respectively. The mode of action test indicated that these derivatives had superior contact and systemic insecticidal activity against M. persicae. In addition, we initially explored whether the foregut and midgut might be the action sites of the target derivatives against M. persicae. Furthermore, a field trial showed that the control of compound I-9 was similar to that of acetamiprid against M. persicae, at a dose of 50 μg/mL; the control rates were 97.8 and 99.2% after 14 and 21 days, respectively. The structure-activity relationship of these analogues provided some important insights for the discovery and development of new insecticides to solve the current pesticide resistance crisis.

Design, Synthesis, and Study of the Insecticidal Activity of Novel Steroidal 1,3,4-Oxadiazoles

A series of novel steroidal derivatives with a substituted 1,3,4-oxadiazole structure was designed and synthesized, and the target compounds were evaluated for their insecticidal activity against five aphid species. Most of the tested compounds exhibited potent insecticidal activity against Eriosoma lanigerum (Hausmann), Myzus persicae, and Aphis citricola. Compounds 20g and 24g displayed the highest activity against E. lanigerum, showing LC₅₀ values of 27.6 and 30.4 μg/mL, respectively. Ultrastructural changes in the midgut cells of E. lanigerum were detected by transmission electron microscopy, indicating that these steroidal oxazole derivatives might exert their insecticidal activity by destroying the mitochondria and nuclear membranes in insect midgut cells. Furthermore, a field trial showed that compound 20g exhibited effects similar to those of the positive controls chlorpyrifos and thiamethoxam against E. lanigerum, reaching a control rate of 89.5% at a dose of 200 μg/mL after 21 days. We also investigated the hydrolysis and metabolism of the target compounds in E. lanigerum by assaying the activities of three insecticide-detoxifying enzymes. Compound 20g at 50 μg/mL exhibited inhibitory action on carboxylesterase similar to the known inhibitor triphenyl phosphate. The above results demonstrate the potential of these steroidal oxazole derivatives to be developed as novel pesticides.