Mechanisms of Cu2+ migration, recovery and detoxification in Cu2+-, SO4(2-) -containing wastewater treatment process with anaerobic granular sludge

The removal of copper and zinc from swine wastewater by anaerobic biological-chemical process: Performance and mechanism

Copper and zinc are often used as feed additives and frequently detected in swine wastewater. Anaerobic granular sludge (AnGS) plays an important role in high-rate anaerobic methanation biotechnologies which are widely applied to treat swine wastewater. The removal of Cu²⁺ and Zn²⁺ by AnGS was investigated in the batch and continuous systems. The results of batch experiments showed the adsorption by AnGS could be a significant method for Cu²⁺ and Zn²⁺ removal with efficiencies of 99 % and 49 % respectively. The sulfide precipitation mediated by AnGS could be another significant pathway for Zn²⁺ removal with efficiency of 18-27 % in Protein/M²⁺ experiments and 16-46 % in SO₄^2-/M²⁺ experiments (M²⁺ represents the total concentration of Cu²⁺ and Zn²⁺). The results of continuous experiment showed, with SO₄^2-/M²⁺ larger than 1.5, the influent Cu²⁺ and Zn²⁺ could be effectively removed in an anaerobic methanation bioreactor and its effluent Cu²⁺and Zn²⁺concentrations were below 1 mg/L and 2 mg/L separately. The main removal mechanism of Cu²⁺and Zn²⁺ in the anaerobic methanation system was that the biological production of sulfide from sulfate was followed by chemical precipitation and reduction. It is helpful for the removal of Cu²⁺ and Zn²⁺ with organic pollutants simultaneously to eliminate environmental risk of swine wastewater.

Anammox and partial denitrification coupling: a review

As a new wastewater biological nitrogen removal process, anammox and partial denitrification coupling not only plays a significant role in the nitrogen cycle, but also holds high engineering application value. Because anammox and some denitrifying bacteria are coupled under harsh living conditions, certain operating conditions and mechanisms of the coupling process are not clear; thus, it is more difficult to control the process, which is why the process has not been widely applied. This paper analyzes the research focusing on the coupling process in recent years, including anammox and partial denitrification coupling process inhibitors such as nitrogen (NH₄⁺, NO₂⁻), organics (toxic and non-toxic organics), and salts. The mechanism of substrate removal in anammox and partial denitrification coupling nitrogen removal is described in detail. Due to the differences in process methods, experimental conditions, and sludge choices between the rapid start-up and stable operation stages of the reactor, there are significant differences in substrate inhibition. Multiple process parameters (such as pH, temperature, dissolved oxygen, redox potential, carbon-to-nitrogen ratio, and sludge) can be adjusted to improve the coupling of anammox and partial denitrification to modify nitrogen removal performance.

As a new wastewater biological nitrogen removal process, anammox and partial denitrification coupling not only plays a significant role in the nitrogen cycle, but also holds high engineering application value.

Morphological control of lanthanide ferrocyanides and their highly efficient catalytic degradation performance toward organic dyes under dark ambient conditions

KCe[FeII(CN)6]·4H2O (CePBA), a Prussian blue analogue, was successfully synthesized with various morphologies and different sizes. CePBA, when used as a heterogeneous catalyst, can rapidly and completely degrade a large number of methylene blue molecules in 30 seconds: 14.5 mg of MB (for each 5 mg of catalyst). The CePBA catalyst is reusable. These are very important parameters for practical applications.

Removal of copper from aqueous solutions by rhizofiltration using genetically modified hairy roots expressing a bacterial Cu-binding protein

The aim of this work was to develop a biotechnological tool to hyperaccumulate high copper (Cu) concentrations from wastewaters. Transgenic tobacco hairy roots were obtained by expressing, either the wild-type version of the gene copC from Pseudomonas fluorescens in the cytoplasm of plant cells (CuHR), or a modified version targeted to the vacuole (CuHR-V). Control hairy roots transformed with the empty vector (HR) were also generated. The roots were incubated in the presence of solutions containing Cu (from 1 to 50 mM). At 5 mM external copper, transgenic hairy roots accumulated twice the amount of copper accumulated by control hairy roots. However, at 50 mM Cu, accumulation in both transgenic and control roots reached similar values. Maximum Cu accumulation achieved by transgenic hairy roots was 45,000 µg g-1 at 50 mM external Cu. Despite the high Cu accumulation, transgenic hairy roots, particularly CuHR-V, showed less toxicity symptoms, in correlation with lower activity of several antioxidant enzymes and lower malondialdehyde (MDA) levels. Moreover, CuHR-V roots displayed low values of the oxidative stress index (OSI) - a global parameter proposed for oxidative stress - indicating that targeting CopC to the vacuole could alleviate the oxidative stress caused by Cu. Our results suggest that expressing copC in transgenic hairy roots is a suitable strategy to obtain Cu-hyperaccumulator hairy roots with less toxicity stress symptoms.

ABBREVIATIONS

APX: ascorbate peroxidase; ATSDR: Agency for Toxic Substances and Disease Registry (U.S.); BCF: bioconcentration factor; CuHR: copper-hairy roots; EDTA: ethylenediamine tetracetic acid; EPA: Environmental Protection Agency (U.S.); GSH: glutathione; HM: heavy metals; HR: control hairy roots; ICP-OES: Inductively Coupled Plasma/Optical Emission Spectrometry; MDA: malondialdehyde; NBT: nitroblue tetrazolium; OD: optical density; OSI: oxidative stress index; PCR: polymerase chain reaction; PVP: polyvynilpirrolidone; PX: peroxidase; ROS: reactive oxygen species; SOD: superoxide dismutase.

Absorption of sulfur dioxide from simulated flue gas by polyethyleneimine-phosphoric acid solution

Clean fuel technologies have been widely developed in current society because fuel combustion can directly bring about the emission of hazardous gasses such as SO2. Flue gas desulfurization by polyethyleneimine (PEI)-phosphoric acid solution is an efficient desulfurization method. In this research, the PEI and the additive H3PO4 were used as absorption solution. SO2 was absorbed by the system and desorbed from the loaded solution. The cycle operation was also analyzed. Some technology conditions such as the concentration of PEI, the temperature, the gas flow rate, the concentration of SO2 and the pH value were experimentally researched. With the optimized process, the absorption efficiency of this system could reach 98% and the desorption efficiency was over 60%, showing good absorption/desorption capability. With this efficient approach, the present study may open a new window for developing high-performance absorbents which can make SO2 be well desorbed from the loaded solution and better reused in the flue gas desulfurization.

Treatment of acid rock drainage using a sulfate-reducing bioreactor with zero-valent iron

This study assessed the bioremediation of acid rock drainage (ARD) in flow-through columns testing zero-valent iron (ZVI) for the first time as the sole exogenous electron donor to drive sulfate-reducing bacteria in permeable reactive barriers. Columns containing ZVI, limestone or a mixture of both materials were inoculated with an anaerobic mixed culture and fed a synthetic ARD containing sulfuric acid and heavy metals (initially copper, and later also cadmium and lead). ZVI significantly enhanced sulfate reduction and the heavy metals were extensively removed (>99.7%). Solid-phase analyses showed that heavy metals were precipitated with biogenic sulfide in the columns packed with ZVI. Excess sulfide was sequestered by iron, preventing the discharge of dissolved sulfide. In the absence of ZVI, heavy metals were also significantly removed (>99.8%) due to precipitation with hydroxide and carbonate ions released from the limestone. Vertical-profiles of heavy metals in the columns packing, at the end of the experiment, demonstrated that the ZVI columns still had excess capacity to remove heavy metals, while the capacity of the limestone control column was approaching saturation. The ZVI provided conditions that enhanced sulfate reduction and generated alkalinity. Collectively, the results demonstrate an innovative passive ARD remediation process using ZVI as sole electron-donor.

A Series of Multifunctional Metal-Organic Frameworks Showing Excellent Luminescent Sensing, Sensitization, and Adsorbent Abilities

A series of highly luminescent-active metal-organic frameworks (MOFs) 1-3 with hierarchical pores have been rationally constructed and fully characterized. The predesigned semi-rigid hexacarboxylate ligand hexa[4-(carboxyphenyl)oxamethyl]-3-oxapentane acid (H6 L) has been adapted with various space-directed N donors (i.e., 2,2'-bipyridine, 4,4'-di(1H-imidazol-1-yl)-1,1'-biphenyl, and 1,3,5-tri(1H-imidazol-1-yl)benzene) from a bidentate V-shape to a tridentate Y-shape. This family of multifunctional MOF materials represents a variety of potential applications in the following aspects: first, as luminescent sensors that show a fast and sensitive detection for pollutant CrO4 (2-) and Cr2 O7 (2-) ions in aqueous media; second, as adsorbents that can rapidly remove harmful organic dyes; third, as an antenna that can effectively sensitize visible-light-emitting Tb(3+) ions. These multifunctional MOF materials combine optical-sensing, adsorption, and sensitization properties, thus are very useful in many potential applications. Furthermore, these materials have proved to be reusable.