Modification of TiO2 by Er3+ and rGO enhancing visible photocatalytic degradation of arsanilic acid.

As a typical wide band gap photocatalyst, titania (TiO2) cannot use the visible light and has fast recombination rate of photogenerated electron-hole pairs. Simultaneous introduction of erbium ion (Er3+) and graphene oxide (rGO) into TiO2 might overcome these two drawbacks. In this study, Er3+ and rGO were co-doped on TiO2 to synthesize Er3+-rGO/TiO2 photocatalyst through a two-step sol-gel method. Based on the UV-visible diffuse reflectance spectra and photoluminescence spectrum, the introduction of Er3+ and rGO increased the visible light absorption efficiency and enhanced the migration of photogenerated electron. Pure TiO2 has almost no photocatalytic activity for arsanilic acid (p-ASA) degradation under visible light irradiation. However, while doping with 2.0 mol% Er3+ and 10.0 mol% rGO, the p-ASA could be completely degraded within 50 min by the Er3+-rGO/TiO2 photocatalyst under visible light irradiation, and most of produced inorganic arsenic was in situ removed by adsorption from the solution. The reactive oxygen species (ROS) reacting with p-ASA was determined and superoxide radical (O2•-) and singlet oxygen (1O2) were the dominant ROS for the oxidation of p-ASA and arsenite. This work provides an approach of introducing Er3+ and rGO to enhance the visible light photocatalytic efficiency of TiO2.

Income inequality and environmental degradation in Egypt: evidence from dynamic ARDL approach.

Over the past four decades, the Egyptian economy has suffered from both income inequality and environmental degradation. This dual problem raises the question about the nature of the relationship between inequality and the environment in a developing country like Egypt. In this regard, the study aims to examine the impact of income inequality on carbon emissions during the period 1975-2017. The analysis considers the ability of the political economy approach compared to the Keynesian trade-off approach to explain the inequality-environment relationship in Egypt. To do this, the novel dynamic autoregressive distributed lags approach is employed to capture the short-run and long-run relationships and to overcome the complications associated with the structure of the widely used autoregressive distributive lags model. The findings show that the relationship between inequality and CO2 emissions is not a trade-off. Rather, inequality leads to environmental deterioration in the long run, but there is no significant effect in the short run. In the long run, a 1% rise in the Gini coefficient increases CO2 emissions by 2.28%. These results support the political economy approach in explaining the inequality-environment nexus. Hence, the economic development policies adopted in Egypt during the past four decades have led to a negative impact on the environment. The study advises economic policy makers in Egypt to adopt income redistribution policies to reduce the severity of income inequality. Improving income distribution has a positive effect on the environment in Egypt.

The environmental impact of remittance inflows in developing countries: evidence from method of moments quantile regression.

Despite the importance of remittance inflows as potential source of incomes for recipient households and one of main contributors to the development process in various developing countries, their environmental effects have been largely neglected in empirical literature. To fill this gap, the current study proposes an extension of the conventional environmental Kuznets curve by performing a modified version based on remittance inflows in both low- and middle-income countries from 1980 to 2014. Using the novel method of moments quantile regression with fixed effect, the outcomes provide evidence of an inverted N-shaped Kuznets curve for remittances at higher carbon dioxide emitters in lower middle-income countries, proving that remittances allow recipient households to shift toward clean energy pattern (production/consumption). We find U-shaped curve for remittances from the 40th to 80th quantiles in upper middle-income countries along with monotonic negative effect on carbon dioxide emissions at highest quantiles (90th and 95th). No significant effect on environment has been outlined at lower carbon dioxide emitters for all panels. Regarding economic growth, an inverted N-shaped curve has been observed across all quantiles in upper middle-income countries and from lower to middle quantiles in low-income countries. Finally, financial development, as control variable, exerts significant mixed effect on carbon dioxide emissions, swung between positive at all quantiles in low- and upper middle-income countries and negative at lower quantiles in low-income countries. Some recommendations were further built in the present study.

Inhibitory effect of oil and fat on denitrification using food waste fermentation liquid as carbon source.

Food waste fermentation liquid (FWFL) can be used as carbon source to enhance nitrogen removal in wastewater treatment. However, the influence of lipid, a common component of food waste, on denitrification remains unclear. In this study, the effect of oil and fat on denitrification process and the underlying mechanisms were investigated using synthetic oil- and fat-bearing carbon source and verified with real FWFL. In the batch experiment, oil and fat had no obvious influence on denitrification, but in the semi-continuous experiment, the denitrification rate in the oil- and fat-added assays decreased to 44% and 38% of that in the control, respectively, after 45 batches. Oil and fat caused sludge floatation, and the floating sludge thickness increased with the continuous operation. Oil/fat-sludge aggregates were observed in the floating sludge and limited gas release. Microbial community analysis indicated that oil and fat did not affect denitrifying bacteria abundance. Limitation of mass transfer might be the main reason for the inhibition of oil and fat on denitrification. In the real FWFL experiment, the denitrification rate in the original and emulsified oil-bearing FWFL decreased to 24% and 56% of that in the demulsifying FWFL, respectively, after 45 batches. These findings indicate the necessity of removing lipids when FWFL is used as denitrification carbon source.

Effect of ultrasonic and ozone pretreatment on the fate of enteric indicator bacteria and antibiotic resistance genes, and anaerobic digestion of dairy wastewater.

In this study, the effect of ultrasound (US), ozone and US combined with ozone (US/ozone) pretreatments on the fate of enteric indicator bacteria and antibiotic resistance genes (ARGs), and anaerobic digestion (AD) of dairy wastewater was investigated. The pretreatment conditions included US power 200 W, ozone concentration 4.2 mg O3/L, and pretreatment time 0-30 min. The results showed that US/ozone pretreatment was effective in the inactivation of enteric indicator bacteria. Total coliforms and enterococci were reduced by 99% and 92% after 30 min US/ozone pretreatment. Pretreatments could not decrease ARGs in absolute concentration, but could decrease ARGs in relative abundance. In the subsequent AD process, methane production increased more than 10% with 20 min ozone or 20 min US/ozone pretreatments. Pretreatment-AD together obviously inhibited the enrichment of ARGs in relative abundance. This study provided a pretreatment way to enhance methane production and to prevent the enrichment of ARGs.