The Application of Advanced Materials on the Water or Wastewater Treatment

Water scarcity is being recognized as a present and future threat to human activity, and, as a consequence, water purification technologies are gaining major worldwide attention. Advanced materials have many properties, such as strong adsorption, enhanced redox, and photocatalytic properties, providing unprecedented opportunities to treat surface water, groundwater, and industrial wastewater that are contaminated with toxic metals, organic and inorganic compounds, bacteria, and viruses. Currently, tremendous progress has been made in development of advanced materials for their environmental applications, and knowledge has been accumulated of the effects of these advanced materials on and their applications in the environment security, recycling, and reuse of raw materials and treatment agents, economic benefits, and potential problems to our society.This special issue aims to provide an up-to-date account of advancement in these areas as well as insights gained through field experience

Heavy Metal Distribution and Groundwater Quality Assessment for a Coastal Area on a Chinese Island

Chongming Island is located in the lower Yangtze Estuary in China. Due to the Leachate from a refuse landfill and the hydrodynamics of the Yangtze Estuary, the groundwater environment is particularly complicated on Chongming Island. Field observations were carried out around the landfill disposal site. The groundwater table, temperature, pH, salinity, and dissolved oxygen were measured in the field by portable equipment, and 192 water samples were collected at eight groundwater sites and one surface water site. Through laboratory analysis we found the highest measured concentration of Cr to be 54.07 μg/L, and the measured concentration of Zn was in the range of 8 1.1 μg/L to more than 200 μg/L, which were both higher than their background values. Strong correlations were found between the heavy metal (Cr, Ni, Cu) concentrations and physico-chemical characteristics (salinity and pH), which indicated that both the landfill and the tides played an important role in the distribution of heavy metal concentrations. Both the BM and PoS Indices were greater than their critical values near the disposal site, indicating groundwater pollution by heavy metals. We show that Cr and Ni are the major heavy metals causing groundwater contamination in the study region

Sunlight mediated enhanced removal of metoprolol using graphitic carbon nitride (g-C3N4)

Graphitic carbon nitride (g-C3N4) is a photocatalyst that has recently been given a lot of attention due to its effectiveness in wastewater and environmental treatment, solar energy utilization, biomedical applications, etc. In this study, g-C3N4 was synthesized and characterized to carry out the degradation of metoprolol tartrate salt (MET), which is classified as an emerging contaminant. MET is one of the most commonly used pharmaceuticals to treat patients with cardiovascular diseases and disorders, a common disease in Malaysia. Recent discoveries of MET in surface waters and drinking water raise awareness and concerns. g-C3N4 was synthesized using solid urea by placing it in a muffle furnace of 550°C for 3 hours. The photocatalytic activities of g-C3N4 were investigated by photodegradation of MET, g-C3N4 of different dosages were added into MET-containing solution, and a dark reaction was carried out for 24 hours for complete adsorption equilibrium. Various physical and chemical analyses were conducted to elucidate the properties of g-C3N4, such as FESEM, FTIR and UV-Vis. The absorbance and reflectance graphs of g-C3N4 show that there will be higher absorption in the visible light spectra. The results show that the optimum dosage to treat 10 ppm of MET is by using 0.3 g of g-C3N4. Under sunlight irradiation of 4 hours, the degradation of MET achieved 54.6% of removal. Hence, it proves that g-C3N4 nanosheet can be applied to remove complex pollutants such as MET under sunlight irradiation. This path is an alternative removal method for MET in a sustainable approach

Simultaneous removal of cadmium and nitrate in aqueous media by nanoscale zerovalent iron (nZVI) and Au doped nZVI particles

Nanoscale zerovalent iron (nZVI) has demonstrated high efficacy for treating nitrate or cadmium (Cd) contamination, but its efficiency for simultaneous removal of nitrate and Cd has not been investigated. This study evaluated the reactivity of nZVI to the co-contaminants and by-product formation, employed different catalysts to reduce nitrite yield from nitrate, and examined the transformation of nZVI after reaction. Nitrate reduction resulted in high solution pH, negatively charged surface of nZVI, formation of Fe3O4 (a stable transformation of nZVI), and no release of ionic iron. Increased pH and negative charge contributed to significant increase in Cd(II) removal capacity (from 40 mg/g to 188 mg/g) with nitrate present. In addition, nitrate reduction by nZVI could be catalyzed by Cd(II): while 30% of nitrate was reduced by nZVI within 2 h in the absence of Cd(II), complete nitrate reduction was observed in the presence of 40 mg-Cd/L due to the formation of Cd islands (Cd(0) and CdO) on the nZVI particles. While nitrate was reduced mostly to ammonium when Cd(II) was not present or at Cd(II) concentrations ≥ 40 mg/L, up to 20% of the initial nitrate was reduced to nitrite at Cd(II) concentrations < 40 mg/L. Among nZVI particles doped with 1 wt. % Cu, Ag, or Au, nZVI deposited with 1 wt. % Au reduced nitrite yield to less than 3% of the initial nitrate, while maintaining a high Cd(II) removal capacity

Effects of nitrate on the treatment of lead contaminated groundwater by nanoscale zerovalent iron

Nanoscale zerovalent iron (nZVI) is efficient for removing Pb(2+) and nitrate from water. However, the influence of nitrate, a common groundwater anion, on Pb(2+) removal by nZVI is not well understood. In this study, we showed that under excess Fe(0) conditions (molar ratio of Fe(0)/nitrate>4), Pb(2+) ions were immobilized more quickly (<5 min) than in nitrate-free systems (∼ 15 min) due to increasing pH. With nitrate in excess (molar ratio of Fe(0)/nitrate<4), nitrate stimulated the formation of crystal PbxFe3-xO4 (ferrite), which provided additional Pb(2+) removal. However, ∼ 7% of immobilized Pb(2+) ions were released into aqueous phase within 2h due to ferrite deformation. Oxidation-reduction potential (ORP) values below -600 mV correlated with excess Fe(0) conditions (complete Pb(2+) immobilization), while ORP values ≥-475 mV characterized excess nitrate conditions (ferrite process and Pb(2+) release occurrence). This study indicates that ORP monitoring is important for proper management of nZVI-based remediation in the subsurface to avoid lead remobilization in the presence of nitrate

The Application of Advanced Materials on the Water or Wastewater Treatment

Water scarcity is being recognized as a present and future threat to human activity, and, as a consequence, water purification technologies are gaining major worldwide attention. Advanced materials have many properties, such as strong adsorption, enhanced redox, and photocatalytic properties, providing unprecedented opportunities to treat surface water, groundwater, and industrial wastewater that are contaminated with toxic metals, organic and inorganic compounds, bacteria, and viruses. Currently, tremendous progress has been made in development of advanced materials for their environmental applications, and knowledge has been accumulated of the effects of these advanced materials on and their applications in the environment security, recycling, and reuse of raw materials and treatment agents, economic benefits, and potential problems to our society.This special issue aims to provide an up-to-date account of advancement in these areas as well as insights gained through field experience

Application of zero-valent iron nanoparticles for the removal of aqueous zinc ions under various experimental conditions.

Application of zero-valent iron nanoparticles (nZVI) for Zn²⁺ removal and its mechanism were discussed. It demonstrated that the uptake of Zn²⁺ by nZVI was efficient. With the solids concentration of 1 g/L nZVI, more than 85% of Zn²⁺ could be removed within 2 h. The pH value and dissolved oxygen (DO) were the important factors of Zn²⁺ removal by nZVI. The DO enhanced the removal efficiency of Zn²⁺. Under the oxygen-contained condition, oxygen corrosion gave the nZVI surface a shell of iron (oxy)hydroxide, which could show high adsorption affinity. The removal efficiency of Zn²⁺ increased with the increasing of the pH. Acidic condition reduced the removal efficiency of Zn²⁺ by nZVI because the existing H⁺ inhibited the formation of iron (oxy)hydroxide. Adsorption and co-precipitation were the most likely mechanism of Zn²⁺ removal by nZVI. The FeOOH-shell could enhance the adsorption efficiency of nZVI. The removal efficiency and selectivity of nZVI particles for Zn²⁺ were higher than Cd²⁺. Furthermore, a continuous flow reactor for engineering application of nZVI was designed and exhibited high removal efficiency for Zn²⁺

A new insight on the core-shell structure of zerovalent iron nanoparticles and its application for Pb(II) sequestration.

Nanoscale zerovalent iron (nZVI) has shown a high efficacy for removing heavy metals from liquid solution. However, its removal capacity has not been fully explored due to its common shell composition (FeOOH). In this study, a much higher removal capacity of Pb(II) is observed (1667 mg Pb(II)/gFe), which is over 100% higher than the highest removal capacity of nZVI reported before. High-resolution X-ray photoelectron spectroscopy (HR-XPS) reveals that through restricting the dehydration process of Fe(OH)3, nZVI can acquire a unique shell, which is composed of 45.5% Fe(OH)3 and 54.5% FeOOH. The presence of Fe(OH)3 suppresses the reduction of Pb(II), but greatly promotes the co-precipitation and adsorption of Pb(II). Combining the ratio of Fe-released to Pb-immobilized and the result of HR-XPS, a reaction between Fe(0) core, Fe(OH)3, and Pb(II) is proposed. The Fe released from the Fe(0) core leads to the core depletion, observed by transmission electron microscopy (TEM) under high Pb(II) loading. While temperature has little influence on the removal capacity, pH affects the removal capacity greatly. pH<4.5 favors Fe dissolution, while pH>4.5 promotes Pb(II) adsorption. Given the high Pb removal capacity via the Fe(OH)3 shell, nZVI can be used to remedy Pb(II) contamination

Application of molecularly imprinted polymers to selective removal of clofibric acid from water.

A new molecularly imprinted polymer (MIP) adsorbent for clofibric acid (CA) was prepared by a non-covalent protocol. Characterization of the obtained MIP was achieved by scanning electron microscopy (SEM) and nitrogen sorption. Sorption experimental results showed that the MIP had excellent binding affinity for CA and the adsorption of CA by MIP was well described by pseudo-second-order model. Scatchard plot analysis revealed that two classes of binding sites were formed in the MIP with dissociation constants of 7.52 ± 0.46 mg L(-1) and 114 ± 4.2 mg L(-1), respectively. The selectivity of MIP demonstrated higher affinity for CA over competitive compound than that of non-imprinted polymers (NIP). The MIP synthesized was used to remove CA from spiked surface water and exhibited significant binding affinity towards CA in the presence of total dissolved solids (TDS). In addition, MIP reusability was demonstrated for at least 12 repeated cycles without significant loss in performance