Synthesis, characterization, and mercury adsorption properties of hybrid mesoporous aluminosilicate sieve prepared with fly ash

AbstractA novel hybrid mesoporous aluminosilicate sieve (HMAS) was prepared with fly ash and impregnated with zeolite A precursors. This improved the mercury adsorption of HMAS compared to original MCM-41. The HMAS was characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption, Fourier transform infrared (FTIR) analysis, transmission electron microscopy (TEM) images and 29Si and 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectra. These showed that the HMAS structure was still retained after impregnated with zeolite A. But the surface area and pore diameter of HMAS decreased due to pore blockage. Adsorption of mercury from aqueous solution was studied on untreated MCM-41and HMAS. The mercury adsorption rate of HMAS was higher than that of origin MCM-41. The adsorption of mercury was investigated on HMAS regarding the pH of mercury solution, initial mercury concentration, and the reaction temperature. The experimental data fit well to Langmuir and Freundlich isotherm models. The Dublin–Radushkevich isotherm and the characterization show that the mercury adsorption on HMAS involved the ion-exchange mechanisms. In addition, the thermodynamic parameters suggest that the adsorption process was endothermic in nature. The adsorption of mercury on HMAS followed the first order kinetics

A Historical Sedimentary Record of Mercury in a Shallow Eutrophic Lake: Impacts of Human Activities and Climate Change

Mercury and its derivatives are hazardous environmental pollutants and could affect the aquatic ecosystems and human health by biomagnification. Lake sediments can provide important historical information regarding changes in pollution levels and thus trace anthropogenic or natural influences. This research investigates the 100-year history of mercury (Hg) deposition in sediments from Chao Lake, a shallow eutrophic lake in China. The results indicate that the Hg deposition history can be separated into three stages (pre-1960s, 1960s–1980s, and post-1980s) over the last 100 years. Before the 1960s, Hg concentrations in the sediment cores varied little and had no spatial difference. Since the 1960s, the concentration of Hg began to increase gradually, and showed a higher concentration of contamination in the western half of the lake region than in the eastern half of the lake region due to all kinds of centralized human-input sources. The influences of anthropogenic factors and hydrological change are revealed by analyzing correlations between Hg and heavy metals (Fe, Co, Cr, Cu, Mn, Pb, and Zn), stable carbon and nitrogen isotopes (δ13C and δ15N), nutrients, particle sizes, and meteorological factors. The results show that Hg pollution intensified after the 1960s, mainly due to hydrological change, rapid regional development and urbanization, and the proliferation of anthropogenic Hg sources. Furthermore, the temperature, wind speed, and evaporation are found to interactively influence the environmental behaviors and environmental fate of Hg

Effects of Hydrological and Climatic Variables on Cyanobacterial Blooms in Four Large Shallow Lakes Fed by the Yangtze River

Shallow lakes, one of the most widespread water bodies in the world, are easily shifted to a new trophic state due to external interferences. Shifting hydrologic conditions and climate change can cause cyanobacterial harmful algal blooms (CyanoHABs) in shallow lakes, which pose serious threats to ecological integrity and human health. This study analyzed the effects of hydrologic and meteorological variables on cyanobacterial blooms in Yangtze-connected lakes (Lake Dongting and Poyang) and isolated lakes (Lake Chao and Tai). The results show that (i) chlorophyll-a (Chl-a) concentration tends to decrease exponentially with increasing relative lake level fluctuations (RLLF) and precipitation, but to increase linearly with increasing wind speed and air temperature; (ii) Chl-a concentrations in lakes were significantly higher when RLLF \u3c 100, precipitation \u3c 2.6 mm, wind speed \u3e 2.6 m s−1, or air temperature \u3e 17.8 °C; (iii) the Chl-a concentration of Yangtze-isolated lakes was more significantly affected by water level amplitude, precipitation, wind speed and air temperature than the Yangtze-connected lakes; (iv) the RLLF and the ratio of wind speed to mean water depth could be innovative coupling factors to examine variation characteristics of Chl-a in shallow lakes with greater correlation than single factors

Dynamic Simulation for Domestic Solid Waste composting Processes. Academia Arena

Abstract: Modeling composting processes is the prerequisite to realize the process control of composting. In this paper, a simulation model for domestic solid waste composting processes was developed based on microbial process kinetics, mass conservation equation, energy conservation equation and water balance. Differential equations describing microbial, substrate, oxygen concentrations, moisture content and temperature profiles were derived. Considering that several factors (temperature, oxygen, moisture and FAS) in the process interacted to composting processes, microbial biomass growth kinetics was described. In order to verify the model, a series of aerobic composting experiments on domestic solid wastes were conducted. Temperature, moisture, microbial biomass growth, oxygen consumption rate and the concentrations of organic components were monitored in the composting processes and also simulated with the developed model. The simulation results were well consistent with the experimental results. It also could be seen from the model that the efficiency of composting processes could be raised and aeration requirements could be reduced by controlling the oxygen concentration in the exhaust air within a proper range. When the range is 8% to 12%, the aeration requirements reduced 79.61%. This result was verified by the composting experiment. When initial moisture content was higher than 66% or lower than 33%, it would significantly reduce the rate of substrate degradation. It indicated the effect of initial moisture content on the composting processes was significant. A simple sensitivity analysis demonstrated that two key parameters in composting modeling to determine were maximum specific growth rate ( max μ ) and yield coefficient (Y Y/S ). Therefore, the composting processes could be optimized by the application of the developed simulation model. [Academia Arena 2010;2(3):76-89]

Effects of dissolved organic matter on mercury speciation in rice rhizosphere amended with sulfur-rich biochar

Natural sulfur (S)-rich biochar (NRB) can be employed as an alternative for traditional S-modified biochar. However, the effect of dissolved organic matter (DOM) on mercury (Hg) speciation in rice rhizosphere soils under natural S-rich biochar application remains unclear. We conducted a pot experiment to study the effects of NRB application on the chemical composition and structure of DOM and the related speciation and availability of Hg in rice rhizosphere. Applying NRB significantly increased the concentration of methylmercury (MeHg) in the rhizosphere soils, which was enhanced with application frequency. This observation can be explained by MeHg immobilization in response to increasing S content in rice rhizosphere soils. We also observed increased molecular weight and functional group complexity of DOM, likely contributing to the decrease in MeHg mobility. Furthermore, the increase in pH and humification of DOM caused by S-rich biochar application generally reduced the concentrations of water-soluble and mercuric-sulfide fraction (easily-available Hg species) and organo-chelated fraction (potentially-available Hg species). Our findings highlight that the application of NRB can reduce the availability of MeHg in rice rhizosphere, thus providing a practical basis for reducing the potential risk of MeHg toxicity

Natural lead-enriched biochar modifies TiO

Due to the rapid development of the modern chemical industry, a large amount of chlorophenol pollutants remain in the environment. It poses a serious threat to the ecological environment and human health. Advanced oxidation technologies (AOPs) have the characteristics of mild reaction conditions and strong oxidation capacity, and are currently recognized as safe and effective pollutant treatment technologies. In this study, natural lead-rich biochar materials were used to activate sodium persulfate to degrade 2,4-dichlorophenol, and natural lead-rich biochar modified TiO2 photocatalytically degraded 2,4-dichlorophenol. Then, using natural lead-rich metal biochar/TiO2 material, photocatalysis combined with active sodium persulfate to degrade 2,4-dichlorophenol. The experimental results show that the combination of photocatalysis and activated sodium persulfate reaction can completely degrade 100 mg/L 2,4-dichlorophenol under UV light for 3 h, and the degradation efficiency is much higher than the sum of the two separate reactions. Quenching experiments show that SO4- • radicals play the most important role in the three free radicals (SO4- •, •OH and •O2- ) in the advanced oxidation combination system. Finally, the reaction mechanism of the two advanced oxidation combined systems are speculated

Study of Composting System of Municipal Solid Waste

Abstract： Three sets of adding Bio-surfactant experiments were conducted to understand composting processes with bio-surfactant. Inoculating Strains Ⅲ(2), Pseudomonas aeruginosa (PA) and Bio-surfactant to MSW system by 0.4%、0.4%、0.008% for Run 1, Run 2, Run 3, respectively. The composting experiments showed that: The system of treatment 1 (0.4% Strains Ⅲ(2)), reduce surface tension between liquid and solid to 36 mN/ml at 24 hours. Compared with the control, the quantity of humic from 10.6% to 18.2% and accumulation H 2 S of outlet gas was around half of the control. Thus, Inoculation composting technology with bio-surfactant is a promised method to enhance composting efficiency and improve composting quality

Groundwater Pollution Prevention and Control: Current Status and Countermeasures

Groundwater is a significant source of drinking water and a strategic resource for China. However, the groundwater quality in China is unoptimistic and China faces a severe situation regarding groundwater environment protection as its groundwater pollution prevention and control started late. Therefore, problems faced by groundwater pollution prevention and control should be researched and targeted countermeasures be proposed to curb the trend of groundwater pollution and improve groundwater quality. The study reviews the existing regulations and policies, management status, and requirements of groundwater pollution prevention and control in China, and predicts the future management trend. The results indicate the following challenges. (1) The groundwater pollution status is still unclear and hierarchical and classified management of groundwater pollution is lacking. (2) The groundwater pollution forms become increasingly complex and the regulatory system requires improvement. (3) The groundwater pollution control becomes increasingly difficult and only few control technologies were applied to underground pollution treatment. (4) The requirements of groundwater environmental management are constantly improving; however, the innovation impetus is insufficient. Therefore, we proposed several countermeasures. The pollution status should be identified through continuous investigation and assessment of groundwater environment in key regions, to support the construction of a hierarchical and classified management system. Intelligent, visualized, and coordinated supervision should be achieved by establishing a multilevel groundwater environmental monitoring network and adopting supervisory measures based on information technologies. Green and sustainable models should be formed and promoted through the experimental implementation of groundwater pollution prevention and control projects and by constructing 21 pilot sites. The original innovation and management capacities should be enhanced by focusing on key technical issues such as groundwater pollution traceability, standards system construction, and development of relevant software with proprietary intellectual property rights