Recovery of phosphate and ammonia from wastewater via struvite precipitation using spent refractory brick gravel from steel industry.

Spent refractory brick (SRB) generated from the steel industry has a high magnesium content. In this study, a procedure was developed to utilize SRB gravels for efficient recovery of phosphate and ammonia from high strength wastewater via struvite (MgNH4PO4∙6H2O(s)) precipitation. Mg2+ and Ca2+ were first leached from SRB gravels using nitric acid solution. Ca2+ in the solution could inhibit struvite precipitation and was sequestered by dosing SO32- to form calcium sulfite (CaSO3(s)). The resulting Mg2+-rich solution was then employed to initiate struvite precipitation for phosphate and ammonia recovery. The optimal precipitation was achieved with a molar ratio of [Mg2+]:[NH3-N]:[PO43-P] = 2:1:2 at pH 9.5. The residual phosphate in the solution can be further removed via the precipitation of calcium phosphate minerals. Overall, 99.6% phosphate and 98.2% ammonia could be recovered and the treated wastewater could meet the discharging standards of ammonia and phosphate. The resulting solids, including calcium sulfite, struvite and calcium phosphate can be potentially used in the cement industry and agriculture sector to achieve sustainable recycle of spent materials.

Evaluation of heavy metal leachability of incinerating recycled aggregate and solidification/stabilization products for construction reuse using TCLP, multi-final pH and EDTA-mediated TCLP leaching tests.

Incinerating recycled aggregate (IRA) produced using bottom ash generated from the incineration of municipal solid wastes can be reused as construction materials and cement-based solidification/stabilization (S/S) can be employed to improve their environmental compatibility. Toxicity characteristic leaching procedure (TCLP) is commonly used to evaluate heavy metal leachability before reuse. However, the applicability of TCLP to IRA and their S/S products can be limited because of their alkaline nature which may cause underestimation of metal release. In this study, the leaching of heavy metals from an IRA and two S/S products, low-strength material (CLSM) and multi-functional regenerated concrete (MRC), were evaluated using TCLP, multi-final pH leaching test and EDTA-mediated TCLP. The results showed that TCLP results generally met the reuse standards. However, the results obtained from multi-final pH leaching test and EDTA-mediated TCLP showed exceedances of reuse standards for Pb and Cu when the final pH was < 5 or in the presence of> 7 mM EDTA. The results suggested that the reuse of IRA or S/S products requires further evaluation of their metal leachability in more harsh environmental conditions. Considering its simplicity, it is suggested that EDTA-mediated TCLP could be used for this purpose.

Biochemical and Physiological Characteristics of Photosynthesis in Plants of Two Calathea Species.

Plants of the genus Calathea possess many leaf colors, and they are economically important because they are widely used as ornamentals for interior landscaping. Physiological performances and photosynthetic capacities of C. insignis and C. makoyana were investigated. The photosynthetic efficiencies of C. insignis and C. makoyana were significantly increased when the photosynthetic photon flux density (PPFD) increased from 0 to 600 µmol photons·m-2·s-1 and became saturated with a further increase in the PPFD. The two Calathea species had lower values of both the light saturation point and maximal photosynthetic rate, which indicated that they are shade plants. No significant differences in predawn Fv/Fm values (close to 0.8) were observed between dark-green (DG) and light-green (LG) leaf sectors in all tested leaves. However, the effective quantum yield of photosystem II largely decreased as the PPFD increased. An increase in the apparent photosynthetic electron transport rate was observed in both species to a maximum at 600 µmol·m-2·s-1 PPFD, following by a decrease to 1500 µmol·m-2·s-1 PPFD. Compared to LG leaf extracts, DG leaf extracts contained higher levels of chlorophyll (Chl) a, Chl b, Chls a + b, carotenoids (Cars), anthocyanins (Ants), flavonoids (Flas), and polyphenols (PPs) in all plants, except for the Ant, Fla and PP contents of C. insignis plants. Calathea insignis also contained significantly higher levels of total protein than did C. makoyana. The adjusted normalized difference vegetation index (NDVI), photochemical reflectance index (PRI), red-green, and flavonol index (FlavI) were significantly correlated to leaf Chls a + b, Cars, Ants, and Flas in C. makoyana, respectively, and can be used as indicators to characterize the physiology of these plants.

Eliminating interference by anthocyanin in chlorophyll estimation of sweet potato (Ipomoea batatas L.) leaves.

BACKGROUND: Spectral reflectance was evaluated for its usefulness as a nondestructive estimation of chlorophyll (Chl) content from three cultivars of sweet potato (Ipomoea batatas L.) with green, yellow, and purple leaves grown in a greenhouse for 22 days. While the green and yellow leaves contain variant amount of photosynthetic pigments without or with little level of anthocyanins, the purple leaves, except large amount of photosynthetic pigments, have high quantity of anthocyanins. RESULTS: For green and yellow leaves, the reciprocal reflectance (R-1) and derived indices incorporating near infrared (NIR) reflectance, [(Rλ)-1 - (RNIR)-1] and [(RNIR/Rλ) - 1], in the green and red edge spectral ranges were shown to be strongly correlated (r2 = 0.8 ~ 0.9) with the chlorophyll content. The root mean square error (RMSE) of the chlorophyll content estimation using these indices was < 50 mg m-2. However, when purple leaves containing high levels of anthocyanins were included in the sample, R-1 in the green spectral range and the above-mentioned indices displayed much weaker correlations with the chlorophyll content. The RMSE of chlorophyll estimation using these indices in the green spectral range sharply increased to > 110 mg m-2 when the sample included purple leaves. The new index, [1 - (Rλ/RNIR)], was therefore inferred and developed to eliminate the distorting effect of anthocyanins on chlorophyll content estimation using reflectance in the green spectral range. For leaves with high levels of anthocyanins, the correlation between [1 - (Rλ/RNIR)] and the chlorophyll content remained strong (r2 = 0.8 ~ 0.9) in the green spectral range, and the RMSE was minimal. CONCLUSION: The reflectance index, [1 - (Rλ/RNIR)], therefore represents a new and useful parameter for estimating leaf chlorophyll content in leaves with any level of anthocyanins such as purple rice leaf.

Iron-oxide embedded solid lipid nanoparticles for magnetically controlled heating and drug delivery.

This paper presents the development of magnetic lipid nanoparticles that could serve as controlled delivery vehicles for releasing encapsulated drugs in a desired manner. The nanoparticles are composed of multiple drugs in lipid matrices, which are solid at body temperature and melt around 45 degrees C to 55 degrees C. In addition, super-paramagnetic gamma-Fe2O3 particles with sizes ranging from 5 to 25 nm are surface modified and dispersed uniformly in the lipid nanoparticles. In the prototype demonstration, lipid nanoparticles with average sizes between 100 and 180 nm were fabricated by high-pressure homogenization at elevated temperatures. When exposed to an alternating magnetic field of 60 kA/m at 25 kHz, a solution containing 2 g/L encapsulated gamma-Fe2O3 particles showed a temperature increase from 37 degrees C to 50 degrees C in 20 min. Meanwhile, the dissipated heat melted the surrounding lipid matrices and resulted in an accelerated release of the encapsulated drugs. Within 20 min, approximately 35% of the encapsulated drug molecules were released from the lipid nanoparticles through diffusion. As such, the presented lipid nanoparticles enable a new scheme that combines magnetic control of heating and drug delivery, which could greatly enhance the performance of encapsulated drugs.