Performance and mechanism of La-Fe metal-organic framework as a highly efficient adsorbent for fluoride removal from mine water

Water fluoride pollution has caused non-negligible harm to the environment and humans,and thus it is crucial to find a suitable treatment technology.In this study,La-Fe@PTA adsorbent was synthesized for the defluoridation of mine water.The results showed that the optimum conditions for defluoridation by La-Fe@PTA were p H close to 7.0,the initial F-concentration of 10 mg/L,the dosage of 0.5 g/L and the adsorption time of 240 min.Compared with SO_4^(2-),Cl^(-),NO_(3)^(-),Ca^(2+)and Mg^(2+),CO_(3)^(2-)and HCO_(3)^(-)presented severer inhibition on fluoride uptake by La-Fe@PTA.The adsorption process fits well with the pseudo-second-order kinetic model and Freundlich model,and the maximum adsorption capacity of Langmuir model was 95 mg/g.Fixed-bed adsorption results indicated that fluoride in practical fluorinated mine water could be effectively removed from 3.6 mg/L to less than 1.5 mg/L within130 bed volume(BV)by using 1.5 g La-Fe@PTA.Furthermore,the adsorbent still had good adsorption capacity after regeneration,which confirms the great application potential of La-Fe@PTA as a fluoride ion adsorbent.The mechanism analysis showed that La-Fe@PTA adsorption of fluorine ions is a physicochemical reaction driven by electrostatic attraction and ion exchange.

Identification of resistant pharmaceuticals in ozonation using QSAR modeling and their fate in electro-peroxone process

The abatements of 89 pharmaceuticals in secondary effluent by ozonation and the electro-peroxone(E-peroxone)process were investigated.Based on the results,a quantitative structure-activity relationship(QSAR)model was developed to explore relationship between chemical structure of pharmaceuticals and their oxidation rates by ozone.The orthogonal projection to latent structure(OPLS)method was used to identify relevant chemical descriptors of the pharmaceuticals,from large number of descriptors,for model development.The resulting QSAR model,based on 44 molecular descriptors related to the ozone reactivity of the pharmaceuticals,showed high goodness of fit(R^(2)=0.963)and predictive power(Q^(2)=0.84).After validation,the model was used to predict second-order rate constants of 491 pharmaceuticals of special concern(k_(O_(3)))including the 89 studied experimentally.The predicted k_(O_(3))values and experimentally determined pseudo-first order rate constants of the pharmaceuticals’abatement during ozonation(k_(OZ))and the E-peroxone process(k_(EP))were then used to assess effects of switching from ozonation to the E-peroxone process on removal of these pharmaceuticals.The results indicate that the E-peroxone process could accelerate the abatement of pharmaceuticals with relatively low ozone reactivity(k_(O_(3))<∼10^(2)M^(−1)⋅s^(−1))than ozonation(3–10 min versus 5–20 min).The validated QSAR model predicted 66 pharmaceuticals to be highly O_(3)-resistant.The developed QSAR model may be used to estimate the ozone reactivity of pharmaceuticals of diverse chemistry and thus predict their fate in ozone-based processes.