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With the rapid development of economy and society, heavy metal and organic contaminants, as a typical combination of mixed contaminants, enter into the environment through multiple pathways and pose a serious threat to human beings. Therefore, there is an urgent need to find an efficient, rapid and non-secondary pollution method to remove them from the water environment. However, it is difficult for traditional water treatment technologies to completely degrade them in a short time. With the continuous progress of nanotechnology, nano-zero-valent iron (nZVI) has become one of the very promising materials for the removal of mixed contaminants from aqueous environments due to its high reducibility, fast reaction rate and environmental friendliness. However, nZVI is prone to agglomeration and oxidation, which limits its practical application. Therefore, this paper reviews the modification methods of nZVI and the problems they face. In addition, the degradation mechanisms of modified nZVI for heavy metals and organic contaminants is also reviewed. The removal of heavy metal-organic mixed contaminants by sodium alginate (SA), cyclodextrin (CD) and chitosan (CS)-modified nZVI was also analyzed in details. Finally, challenges and future perspectives are discussed, as well as providing a more comprehensive perspective on nanomaterial modification.

Organic dyes and heavy metals are renowned environmental contaminants due to their hazardous, long life time in the environment, and capability to accumulate into the human body. Most heavy metals are accumulated naturally, however only some are derived from anthropogenic sources. In the recent decades, metal organic framework (MOF) and their most fashionable derivatives are extensively examined to eradicate heavy metals and organic dye substances from polluted water as powerful adsorbent materials. MOFs have forever exposed attractive applications in adsorption technologies and membrane separation, among which water-stable MOFs are predominantly important in wastewater treatment (WWT) relevance. MOFs like metal-organic polymers, hybrid organic–inorganic materials, organic zeolite materials and coordination polymers have increased awareness and many of the MOFs have been synthesized to eradicate heavy metals and organic dyes from waste water, because of their outstanding characteristics like large surface area, stability, greater porosity which make the MOF a strong and powerful adsorbent. In this paper, we discussed about the removal of hazardous heavy metals and organic dyes using MOF materials and their analogues as strong adsorbents for contaminated waste water.

A PIXE analysis was performed at Nishina Memorial Cyclotron Center (NMCC) for some leaf and ash samples from bottom of a waste pond at the Fankou Pb-Zn mine, Guangdong, China. The ash is the product after burning "Luzhu" that is planted by the mine for the environmental cleaning purpose in the waste pond. The PIXE detected high level of zinc and lead for both of the samples. As Fankou is one of the largest Pb-Zn producer in Asia, careful and urgent treatment is necessary for the deposited ash in the pond. This analysis was performed due to a request of analysis of the Fankou mine to promote environmental protection of the area.

It has been reported that edible mushrooms are able to enrich the concentrations of several heavy metals. The Cd has especially drawn attention due to its high toxicity. By using PIXE analysis for the determination of the heavy metals it is possible to obtain a screening of the content of a wide number of elements. By analysing different species it is shown that one or a few elements may be characteristic for a single species. It is especially remarkable that several species of the family Agaricaceae are enriching Ag to a very high degree (up to 200 ppm).

Geosiphon pyriforme is a unique symbiosis between a fungus, belonging to the arbuscular mycorrhizal (AM) fungi, and a cyanobacteria (blue-green algae). Since more than 80 % of the land plant species form an AM, the importance of this symbiosis becomes evident. In our research on heavy metal uptake and resistance of plants, Geosiphon is used as a model system for the AM symbiosis. Whilst we have studied heavy metal uptake of Geosiphon pyriforme from a macroscopic point of view we will now present first and preliminary results of element distributions in heavy metal stressed and non-stressed cryo-sections of Geoslphon pyriforme.

Chinampas are island plots (500-1000 m²) constructed of soil scooped from the bottom of the lake and surrounded by canals. Over 40 agricultural species, including vegetables, cereals, and flowers, are produced on chinampas and consumed by approximately 100,000 people. This agro-ecosystem, once one of the most diverse and productive, at present is at risk of disappearing, mainly as a consequence of the severe pollution of the irrigation water. To evaluate the relationship between the accumulation of metals and physical soil properties, total trace metals Fe, Cu, Mn and Zn and total heavy metals Pb, Ni, and Cr in soils were determined by Particle Induced X-Ray Emission (PIXE). This method provides a very suitable technique for treating a large number of samples because sample preparation is simple and determination of a large number of elements is simultaneous. Three sites were chosen because of their long history of pollution: Xochimilco, San Luis Tlaxialtemalco and Mixquic in Mexico City. Soil properties were determined by conventional analytical methods. Soils were found to be high in organic matter content, high in sodicity and salinity, and with an alkaline pH. The metals present in the samples are in the following order of abundance: Fe>Mn>Cr>Zn>Cu>Pb.

Phytoremediation is a technology for remediation of contaminated soils. In this study, we used a submilli-PIXE camera to analyze plants and soils from a shooting range. Some heavy metals were rapidly and easily detected in these samples. Element dot-maps of the plant show Cu and Pb accumulated in the epidermis of subterranean stems and the venation of leaves. From these findings, it is possible to map the distribution of heavy metals and to detail their location in the plant, using the submilli-PIXE camera. PIXE analysis is an effective tool for undertaking phytoremediation research.

Lead (Pb), cadmium (Cd) and uranium (U) present no known biological function but are toxic in various concentration ranges. Pb and Cd lead generally to nephrotoxicity consisting in proximal renal tubular dysfunction and accumulation while U has been reported to induce chemical kidney toxicity, functional and histological damages being as well mainly observed in proximal tubule cells. This work address the question of Cd, Pb, and U cytotoxicity, intracellular accumulation and repartition after acute intoxication of renal proximal tubule epithelial cells. After cells exposure to different concentrations of metals for various times, morphological changes were observed and intracellular concentrations and distributions of toxic metals were specified by PIXE coupled to RBS. Cell viability, measured by biochemical tests, was used as toxicity indicator. A direct correlation between cytotoxicity and intracellular accumulation in renal epithelial cells have been established. Finally, intracellular Pb and U localizations were detected while Cd was found to be uniformly distributed in renal cells.

Industrial wastes are considered as critical factors for disturbing natural ecosystems. The East Calcutta Wetlands, a Ramsar site in West Bengal, India, receives composite industrial effluents, subsequently bringing various kinds of heavy metals throughout the year. This wastewater is being utilized by the local people for pisciculture. The present investigation was carried out to study 1) elemental distribution various components of the wetland and 2) potentiality of water hyacinth in metal amelioration. Water and sediments were collected from four different spots along a wastewater-carrying canal having a stretch of 40km from the source point to the final confluence with river and from the wastewater fed fishpond. Fish (three common carps viz. Labeo rohita, Cirrhinus mrigala and Oreochromis niloticus) and water hyacinth were collected from fishpond mentioned above. Samples were analyzed by PIXE with 3MeV tandem Pelletron. Cr, which is a known metal contaminant of tannery effluent, was detected along with S, K, Ca, Ti, V, Mn, Fe, Ni, Cu, Zn, As, Br, Rb, Sr, Zr. Variable concentrations of some elements like Ca, Fe, Zn in different fish organs was noted in the experiment. Accumulation of Cr, Cu from the water bodies by water hyacinth suggesting their crucial role in heavy metal amelioration.

The enrichment procedure of heavy metals (Fe³⁺, Co²⁺, and Hg²⁺) in water was examined in conjunction with in-air PIXE. The preconcentration step consisted of adsorption of dibenzyldithiocarbamate complexes of the metal ions onto dibenzylidene-D-sorbitol gels. The colloidal gels in solutions were then collected on a nuclepore membrane for direct irradiation by proton beams in a system of vertical beam type in-air PIXE. The amounts of the chemicals used in the enrichment were minimized to prepare thin target specimens with the homogeneous composition. The metal-recovery in the preconcentration step was confirmed to be quantitative in a wide range of the concentrations. The reproducibility and detection limit were shown and discussed for the present setup of PIXE analysis in our laboratory.

A metal-preconcentration procedure, which consists of a combination of chelation by dibenzyldithiocarbamate ions with subsequent condensation into dibenzylidene-D-sorbitol gels, has been reformed by using Zr as an internal standard. The colloidal gels formed in solutions were collected on a nuclepore filter for direct irradiation by 3 MeV proton beams in a system of vertical beam type in-air PIXE. The methodology was tested for simultaneous determination of the concentrations of seven metals (Fe, Co, Ni, Cu, Cd, Hg, Pb) in 25 ml of an aqueous sample. A good linear relationship was obtained between the nominal concentration and the elemental X-ray yields normalized with Zr-K_α ones. Absolute values of concentration in the sample solutions can be determined with an experimental error less than ±14 % in the 5-100 ppb range by employing published data pertinent to the inner shell ionization and subsequent X-ray emission of the heavy metals.

The electronics industry uses high volumes of heavy metals in its production processes. Many of these heavy metals can end up in water and can be very difficult to remove due to the different forms that the heavy metal can exist in. Special design characteristics should be used to produce filters to remove heavy metals. In this study, we identify the different species of heavy metals and describe a method that has been tested for removing all types of species for heavy metals from water. This filtration technique utilizes multiple layers to ensure the removal of soluble, insoluble and complex species of heavy metals in water. The testing was done with a complex solution of lead according to NSF/American National Standards Institute (ANSI) standard 53 for the removal of lead at pH 8.5, using a combination of soluble, particulate and semi-insoluble lead. Filters were compared to standard, commercially available, gravity pitcher filters. The testing showed that the newly designed filter removed over 80 gallons of lead below the drinking water limit, compared to a standard filter which failed immediately. When trying to remove heavy metals from water, special care needs to be used in the design of the system to ensure the removal of all species of heavy metals.

The fate of different trace elements and radio nuclides in the new ZWILAG nuclear waste treatment plant (Switzerland) has been modelled, in order to predict and check the transport behaviour of the volatile species and their distribution in the plant. Calculations show that for active waste from medicine, industry, research (MIR waste) only Zn and Cs have stable gaseous species at 1200°C. The investigations confirm the efficiency of the examined flue gas cleaning system.

Mn co-precipitation method combined with Raman spectroscopy were used to determine trace heavy metals (copper, zinc, cadmium and lead) in water sample. Different concentrations of heavy metals including copper, zinc, cadmium and lead in water samples were separated and enriched by Mn²⁺-phen-SCN- ternary complex co-precipitation procedure. The Raman spectra of co-precipitation sediments were collected using confocal micro-Raman spectrometry. Different preprocessing treatments and regression calibration methods were compared. The best models using partial least squares regression (PLS) of copper, zinc, cadmium and lead were built with a correlation coefficient of prediction (R_p) of 0.979, 0.964, 0.956 and 0.972, respectively, and the root mean square error of prediction (RMSEP) of 6.587, 9.046, 9.998 and 7.751 μg/kg, respectively. The co-precipitation procedure combined with Raman spectroscopy method are feasible to detect the amount of heavy metals in water.

We report the cloning and characterization of two new metallothionein (MT) genes (cDNAs) isolated from the ciliated protozoa Tetrahymena rostrata (named as TrosMTT1 and TrosMTT2). TrosMTT1 protein is included into the TetrahymenaCdMT subfamily, due to its similarity to T. thermophila MTT1 and its overexpression under Cd exposure, while TrosMTT2 is identified as a CuMT, due to its similarity to TpigMT-2 and its significant induction by copper. Both are also multi-stress-inducible genes because they are induced, at lower level, by other heavy metals. These two new TetrahymenaMTs complete the actual view of this protein superfamily, and corroborate the unique features of ciliate MTs.

Each heavy metal's pollution of the sedimentary column is evaluated by using 108 cm K1 columnar sediment samples of Yalu River estuary watercourse. The potential ecological harm index of the sedimentary column was proposed by a Swedish scholar Hakanson. The results show that it had a great influence on the result by using different background values to evaluate. Pollution level is generally low with choosing pre-industrial world sediment of high evaluation of heavy metal. Average of heavy metals is obviously on the high side to evaluate by China and the DPRK Platform Shale for reference rating. The potential ecological risk degree of the region can better be reflected by using Chinese waters background values and Yalu River estuary background values of heavy metals.

Dissolved organic carbon (DOC) washing has been proved that it could remove heavy metals effectively from contaminated soil. Addition of Ca or Mg into an acid aqueous solution was known promoting the removal for heavy metals. The object of this study was employing mixture solutions prepared using CaCl_2(aq), MgCl_2(aq), and the liquid fertilizer for remediation of a soil severely contaminated with Cr (918 ppm), Cu (1015 ppm), Zn (1105 ppm), and Ni (529 ppm). Effect of Ca and Mg additions on the removal was examined. When soil washings were conducted using the Ca/Mg solutions, only content of Zn remained in soil favored the level of control standard. The DOC substantially elevated removal efficiency of metal during the washing. Two soil washes using a 4000 ppm DOC/0.1M CaCl₂/0.1M MgCl₂ solution with a of pH 2.0 at 25°C removed approximately 68%, 70%, 69%, and 9% of Cu, Ni, Zn, and Cr respectively. Combined action from the Ca²⁺, Mg²⁺, and proton replacements as well as the organic complexation brought the removal of metals to a maximum level.

Excessive heavy metals contents in sewage sludge maybe hinder the recycling of the sludge and should be mitigated effectively using engineered processes such stabilization as reported. In this work, Sorel cement is used as additive to stablize heavy metals present in sewage sludge. It was found that the contents of Zn, Cu, As, Cr, and Pb in sewage sludge were stabilized as high as 96%, 87%, 84%, 99% and 92%, respectively in the leachability test. The sequential extraction procedure tests showed that the increase of immobile fractions of heavy metals in mixtures, e.g. organic or residual forms, inhibited the transferability of heavy metals to the solution. In addition, the SEM photos of the stabilized microstructures proved that hydration of Sorel cement was changed with various ratios. Therefore, the increase of pH towards highly alkaline value and the formation of ternary hydration in the mixtures appear to have developed to stable heavy metals in sewage sludge.

Soil, sediment, water and sugarcane plant stem around Ewekoro Cement Factory in Ogun state, South Western Nigeria were assessed for heavy metals (Cd, Pb and Zn) contamination, exchangeable bases and pH over a range of about half kilometer from the factory during the wet (harvest) season of 2008. Bioavailability of Zn (as the only heavy metals detected) in sugarcane plant stem was determined as well. The metal concentrations in topsoil ranged from 35.65 ± 0.29 to 28.45 ± 1.60; 14.10 ± 0.44 to 9.65 ± 0.84; 2.43 ± 0.04 to 1.90 ± 0.08 mgKg-1 for Zn, Pb and Cd respectively while in subsoil; it ranged from 29.56 ± 0.50 to 18.53 ± 1.63; 8.21 ± 1.53 to 7.34 ± 0.67; 1.93 ± 0.03 to 1.19 ± 0.09 for Zn, Pb and Cd respectively. There is reasonable spatial correlation of Zn to Cd and Zn to Zn in soil and sugarcane (R2 = 0.699; R2 = 0.665) respectively.

This work describes the experimental studies on the influence of the heavy metals copper (Cu) and zinc (Zn) in different conditions of the fermentation of A.corymbifera using corn steep liquor 6% added with the heavy metals 2 and 4 mM concentrations. The experiments were incubated in orbital shaker at 150 rpm, at temperature of 28°C during 96 hours. The biomass was removed by vacuum filtration, lyophilized and, evaluated by gravimetry. Chitin and chitosan were extracted by alkali and acid treatment and characterized by Infrared Spectroscopy (FTIR). The higher yield of the biomass was obtained in the condition copper 4mM (6.97g/L). The chitosan production (44.5mg/g of biomass) in the 4mM condition, and the copper 2mM (67.29mg/g of biomass) were observed. The chitosan acetylating degrees was 81 and 88%, respectively. These results suggest that the metals copper and zinc promoted an increase in the yield of chitosan, indicating that these metals influence the chitin deacetylase action, for the chitosan production by A. corymbifera. The strategies used for increase the chitosan production suggest A. corymbifera as biopolymer source.