No abstract

A continuous fixed-bed column study has been used to evaluate phosphate adsorption performance of U-D-Na which was functionalized by the cheap NaCl reagent after simple ultrasonic purification of diatomite. Experimentally, various effect factors, the flow rate, the initial phosphate concentration， and the bed height on breakthrough time of fixed column were studied. Experimental results showed that the breakthrough time declined with the increase of inlet phosphorous concentration and feed rate, whereas the increase of bed height turned out to significantly prolong the breakthrough time. The dynamic adsorption data could better be fitted by the Thomas model, with the correlation coefficients obtained, R 2 >0.9000 at the majority of operating conditions (5/7). At least thrice loop of adsorption and desorption was achieved with 0.1 M hydrochloric acid eluent and deionized water. The results proved that U-D-Na could be used as a better alternative phosphate adsorbent from wastewater in a continuous column process.

BACKGROUND: The adsorption removal of phenol onto bentonite that was prepared by the traditional hydrothermal method has been widely studied; especially, surfactant-modified bentonite has achieved an exclusive position on effective removal to phenol. However, the adsorption performance of the bentonite functionalized by double-carbon chain surfactants in a microwave field for phenol is relatively low. The study on the fabrication of organobentonite by microwave-assistance to remove organic pollutants still needs to be investigated. RESULTS:The adsorption performance of bentonite was enhanced after functionalizing with Dihexadecyldimethylammonium Bromide (D1621). FTIR and XRD patterns revealed that D1621 was successfully intercalated into bentonite, and the interval space was increased by 1.54 to 1.84 nm. The optimized preparation condition was obtained at a molar ratio (D1621: Bentonite) of 0.36, solid-liquid ratio (D1621 + Bent: water) of 0.12, microwave mode of Med, and thermal radiation for 6 min based on the indicator of phenol adsorption uptake. An excellent removal rate for phenol was observed at pH 2 to 7 and room temperature in adsorption tests. The adsorption process was spontaneous at room temperature according to thermodynamic parameters, and it agrees with Freundlich (R 2 = 0.9781) and pseudo-second-order (R 2 = 0.9999) models, validating a chemisorption process.CONCLUSION: The D1621-Bent perpetrated by using the microwave-assisted heating method was proven to be a reliable adsorbent for phenol in water. The adsorption performance of bentonite on phenol was remarkably enhanced after the introduction of organic modifiers.

Chlorothalonil is widely used to control fungal diseases and it is usually detected in the environment. The phototransformation is an important process to remove Chlorothalonil from the aquatic environment. The mesoporous ammonium phosphotungstate/silica catalyst (NH4PW/SiO2) was synthesized from cetyl trimethyl ammonium bromide (CTAB) and tetraethoxysilane (TEOS) as raw materials by adding insoluble ammonium phosphotungstate into the alkaline alcohol-water system by sol-gel method. The structure of NH4PW/SiO2 was characterized by X-Ray Diffractomer (XRD), Brunauer-Emmett-Teller (BET) and Fourier Transform infrared spectroscopy (FT-IR). The photocatalytic activity of NH4PW/SiO2 was evaluated by using the organic pesticide chlorothalonil as a model reactant. The result indicated that when the dosage of NH4PW/SiO2 is 0.02 g, the illumination is 180 min, the concentration of chlorothalonil is 5 mg/L, pH = 5, the degradation effect is better, and the degradation rate reaches 83.23%. The results contributed to understanding of chlorothalonil phototransformation and the potential of mesoporous SiO2 to effectively enhance the photocatalytic activity of NH4PW (64.16%) to reduce aquatic toxicity and pollution of chlorothalonil.

A low-cost functionalization method was used to treat diatomite, and an efficient adsorbent for ammonia nitrogen was prepared by optimizing the functionalization conditions. The functionalized diatomite (DTCA-Na) was characterized by SEM, EDS, BET, XRD, FT-IR and TG. The results demonstrate that DTCA-Na has excellent adsorption performance after being modified with H2SO4 (60.00 wt.%), NaCl (5.00 wt.%) and calcination at 400 °C for 2 h. While studying the effect of adsorption factors on the removal of ammonia nitrogen, the kinetic and thermodynamic behaviors in the adsorption process were discussed. The removal efficiency of the simulated wastewater with the initial ammonia nitrogen concentration of 10.00 mg/L by the DTCA-Na was more than 80% when the contact time was 60 min, pH was 6-10, the dosage of adsorbent was 1.00 g, the temperature was 25 °C. The adsorption process of ammonia nitrogen was conformed to the pseudo-first-order and Langmuir isothermal model. The removal efficiency of ammonia nitrogen was still above 80% after 5 times adsorption-desorption experiments. The DTCA-Na has a brighter prospect of application in the field of ammonia nitrogen wastewater treatment due to its excellent adsorption performance and low-cost advantage.