Phosphate concentrates are widely used as primary sources in the production of fertilizers worldwide, but the efficient removal of dolomite from apatite in flotation relies heavily on selective depressants. Conventional apatite depressants such as sulfuric and phosphoric acid inevitably cause serious environmental pollution . It is urgent to explore green and efficient depressants to substitute conventional ones for the clean production of phosphate concentrate. In this work, iminodisuccinic acid (IDS) was explored as an efficient and environmental-friendly dolomite depressant in the direct flotation of apatite from dolomite. The depression performances were evaluated by micro-flotation and the interaction mechanism was revealed through adsorption capacity, Microcalorimetry , Zeta potential , Fourier Transform Infrared (FTIR), X-ray Photoelectron Spectroscopy (XPS) and Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) measurements. Mico-flotation results showed that IDS selectively depressed dolomite but hardly affected apatite flotation, improving the separation efficiency and upgrading the quality of apatite concentrates successfully. Mechanism study demonstrated that IDS preferentially adsorbed on dolomite due to its higher affinity to Mg sites on dolomite. IDS was dominantly chelated with Mg sites to form octahedral complexing structure via the coordination of COO − with Mg sites. While IDS was weakly adsorbed on apatite thought weak hydrogen bond between F sits of apatite with carboxyl within IDS. The pre-adsorption of IDS impeded NaOL adsorption on dolomite, but didn’t influence the NaOL adsorption on apatite. The work proved that IDS could be used as a green and selective dolomite depressant for the clean flotation of apatite from dolomite, which is of great importance for the sustainable production of fertilizer.
Given the severe threat posed by heavy metal pollution to both the ecological environment and human health, the development of green, efficient and sustainable adsorbents has become a major research focus. Herein, a novel heavy metal ions adsorbent (De-UiO-66-IDSA) was synthesized by functionalizing defect UiO-66 with the biodegradable chelating agent iminodisuccinic acid (IDSA). The effects of different factors on the adsorption of Pb 2+ , Cu 2+ and Cd 2+ by UiO-66-IDSA were investigated, including IDSA loading, contact time, adsorbent dosage and pH. Batch adsorption experiments showed that the adsorption kinetics followed PSO model, while the isotherm data were best described by the Langmuir model, indicating a monolayer chemisorption process. The maximum adsorption capacities for Pb 2+ , Cu 2+ and Cd 2+ were 377.40, 163.60, and 204.10 mg/g at 298 K, respectively and the adsorption was spontaneous and endothermic. Moreover, regeneration experiments demonstrated that the adsorbent retained over 75 % of its removal efficiency for all three metal ions after 5 cycles. These results highlight the great potential of De-UiO-66-IDSA as a green, high-performance, and a regenerable adsorbent capable of effectively eliminating heavy metal ions from aqueous media.
Yifei Zhang,Yishan Sun,Weiqing Li,Jiayu Li,Rongqiong Xu,Jiarui Du,Zesong Li,Guibin Li,Kejun Yang
To explore the effects of iminodisuccinic acid (a chelating agent) on maize (Zea maysL.) seed germination under lead (Pb) stress, we comparatively analyzed the effects of applying different concentrations of iminodisuccinic acid (0, 5, 20, and 100 mmol·dm−3) and combined an addition of exogenous substances regulating reactive oxygen species production on maize seed germination, seedling growth, H2O2content, NADPH oxidase activity, and antioxidant enzyme activities under Pb-stressed and Pb-free conditions. Iminodisuccinic acid (100 mmol·dm−3) significantly delayed seed germination under normal germination conditions and alleviated the inhibitory effects of Pb stress (20 mmol·dm−3) on seed germination. Under normal conditions (without Pb stress), the iminodisuccinic acid-induced inhibition of seed germination was enhanced by treatment with dimethylthiourea (a specific scavenger of reactive oxygen species) or diphenyleneiodonium chloride (a specific inhibitor of NADPH oxidase), but diminished by treatment with H2O2, CaCl2, diethyldithiocarbamic acid (a specific inhibitor of superoxide dismutase), or aminotriazole (a specific inhibitor of catalase). Under Pb stress, iminodisuccinic acid partially eliminated the excessive H2O2accumulation, improved superoxide dismutase and catalase activity, and weakened the high NADPH oxidase activity. In addition, Ca2+chelation may be essential for maintaining the reactive oxygen species’ balance and improving seed germination and seedling growth by iminodisuccinic acid supplementation in maize under Pb stress. The proposed iminodisuccinic acid supplementation-based method improved maize seed germination in Pb-polluted soil.Keywords:maize;chelator;lead stress;ROS;hydrogen peroxide;NADPH oxidase;seed germination
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