<p>Equilibrium isotherms and the adsorption kinetics of heavy metals onto chitosan were studied experimentally. Chitosan, a biopolymer produced from crustacean shells, has applications in various areas, particularly in drinking water and wastewater treatment due to its ability to remove metallic ions from solutions. The adsorption capacity of chitosan depends on a number of parameters: deacetylation degree, molecular weight, particle size and crystallinity. The purpose of this work was to study the adsorption of copper, zinc, mercury, and arsenic on chitosan produced from shrimp shells at a laboratory level.</p><p>The experimental work involved the determination of the adsorption isotherms for each metallic ion in a batch system. The resulting isotherms were fitted using the Langmuir model and the parameters of the equation were determined. Kinetic studies of adsorption for different metallic ions at different concentrations and with different particle sizes were performed in batch and column systems. Simplified models such as pseudo-first-order, pseudo-second-order, and intra-particle diffusion equations were used to determine the rate-controlling step. Some preliminary studies were carried out to address the application of chitosan as an adsorbent in the removal of heavy metals or other metallic ions from natural water and wastewater. The regeneration of chitosan was also studied.</p><p>The results showed that the adsorption capacity depends strongly on pH and on the species of metallic ions in the solution. The optimum pH value for the metallic cation adsorption was between 4 and 6, whereas for arsenic adsorption it was about 3. When the pH is not controlled, the adsorption capacity is independent of the initial pH with the solution reaching a final pH of about 7. It was also found that the Langmuir equation described very well the experimental adsorption data for each metallic ion. The adsorption capacity for the metals on chitosan follows the sequence Hg>Cu>Zn>As.</p><p>The study of the adsorption kinetics of these metallic ions shows that the particle size has a significant influence on the metal uptake rate for copper; but that it has only a slight influence on the adsorption rate of zinc and mercury in the range studied. Arsenic adsorption exhibited an interesting behaviour which depends strongly on the pH of the solution; the uptake increased at short adsorption times and then decreased at long times. The analysis of kinetic models showed that the pseudo-second-order adsorption mechanism is predominant, and the overall rate of the metallic ion adsorption process is therefore controlled by adsorption reactions and not by mass transfer for the range of particle sizes examined in this study.</p><p>With regard to the regeneration of chitosan, it was found that sodium hydroxide is a good agent for zinc and arsenic desorption, whereas ammonium sulphate and sodium chloride were the most suitable for copper and mercury desorption, respectively. The ability of chitosan to remove arsenic from natural water, and copper and zinc from mining waste water was verified. The use of these results for designing purposes is a subject for future work.</p>

Heavy-metal pollution is an issue of concern in estuaries such as Biscayne Bay that are heavily influenced by agricultural, urban, and harbor activities. The goals of this study were to provide a state of the bay assessment that can be used to interpret changes that have occurred over the past 60 years in Biscayne Bay, to provide a baseline to compare changes in the ecosystems during and after execution of the Comprehensive Everglades Restorations Plan (CERP), and to determine if benthic foraminiferal assemblages in Biscayne Bay reflect heavy-metal contamination in sediments. Surficial samples were collected at 147 sites throughout the bay. Analyses included geochemical assessment of the mud fraction for 32 chemical parameters, grain-size analysis, and assessment of foraminiferal assemblages at the genus level. Geochemical analyses revealed elevated concentrations of a suite of heavy metals in the sediments of the northern bay, between Miami and Key Biscayne, and the periphery of the southern bay from Black Creek Canal south to Turkey Point. Cluster analysis, multi-dimensional scaling, and multivariate-correlation analyses revealed three distinct foraminiferal assemblages. One assemblage, characteristic of the northern bay, was defined by stress-tolerant taxa including Ammonia, Cribroelphidium, Nonion, and Haynesina, which were present in low abundances. Distribution of this assemblage correlated with the most elevated concentrations of heavy metals. The assemblage that defined the southwestern margin of the bay was dominated by Ammonia and Quinqueloculina. This assemblage is characterized by the lowest diversities and highest abundances, and is likely influenced by both reduced salinity and elevated organic-carbon concentrations.

The Manatee River Watershed (Manatee County, FL) has experienced heavy anthropogenic development over the last 100 years and was relatively pristine previous to this development. The population growth within the watershed has surpassed the national trends and has doubled in the last 30 years. The heavy anthropogenic development has led to depletion in natural resources, nutrient loading, coastal erosion, and increased pollution. This study constructs records of sedimentological processes to compare the pre-development records to the past 100 years of anthropogenic development. The first portion of this study identifies specific changes in sedimentation attributed to anthropogenic activity in the Manatee River. Anthropogenic development has increased the input of terrigenous material into the river by as much as an order of magnitude (0.3-3.0 g/cm2/yr) over three periods; 1) the predevelopment period (1900-1941), 2) the agricultural development period (1941-1970's), and 3) the urban development period (1970's-2010). The second portion of this study examines records of heavy metal (As, Cu, Pb) enrichment in the Manatee River. There are areas in the Manatee River that currently have, or recently have had, concentrations of heavy metals above the EPA regional screening levels. Throughout all of the Manatee River sediment cores there has been a continuous increase in the concentration of arsenic (0.32-20.91 ppm), lead (0.35-35.79 ppm) and copper (1.49-49.55 ppm) from 1900-2010. The third portion of this study utilizes calcareous tests from benthic foraminifera (Ammonia beccarii) in the longest sediment core to determine the Mg/Ca, 18O/ 16O, and 13C/ 12C ratios as proxies for river water temperature, salinity and nutrient content. These proxies allow for the assessment of changes in rates and range of river water parameters from the pre-anthropogenic to the anthropogenic periods. A Manatee River temperature record, precipitation/evaporation record and nutrification record have been constructed for the last 450 years (1550-2009 CE). These records are necessary to inform and enhance future coastal resource management practices.

Deep Bay is located in the northwestern coast of Hong Kong (HK), where brackish water from the Pearl River Estuary meets and interacts with fresh water from Shenzhen River and Yuen Long Creek. A review of published material in this study indicates rapid economic and industrial developments can be found in Hong Kong and Pearl River Delta (PRD) region in the last 60years, which would have contaminated the sediment in Deep Bay with heavy metals. To examine the nature of metal contamination history, two 2m-long sediment cores are collected from the mud flat of Deep Bay, and the chemical and physical properties of the sediment sequence analyzed. Small disturbance of sediment profile is observed by the fluctuation of 210Pb signal, and constant rate of supply (CRS) model is applied for the calculation of sedimentation rate which is estimated to be 1.82cm/year.137Cs dating resolves two peaks for the radionuclide at 28cm and 109cm, as well as the onset of excessive 137Cs activity at 135cm, which are connected to the Chernobyl accident in 1986 and the banning and beginning of atmospheric testing of nuclear weapons in 1963 and 1950 respectively. Particle size analysis shows the core sediments are predominantly silt (4-64μm) and clay(<4μm). Enrichment factor of metal concentration displays that Cd, Cr, Cu and Zn has been significantly enriched since the 1950s, and hence 3 phases of metal enrichment could be identified: 1) insignificant anthropogenic input in preindustrial period before 1950, 2) significant enrichment of metal from anthropogenic sources during industrial stage in HK from 1950 to 1980, and 3) a further increase of metal enrichment after the introduction of new town development in northwestern part of HK and Chinese economic reform since 1980. Among the metals in the sediments at depth over 70cm, Cu and Zn are found to be exceeded the Lower Chemical Exceedance Level of the sediment quality criteria given by the Hong Kong Environmental Protection Department; hence, the metals would impose threats to the natural environment once they are released back to water column by changes to physical conditions. To evaluate the extent of environmental threats, future studies could focus on the bioavailability of the metals and the interaction of metals in sediments and water with organisms in the ecosystem of Deep Bay. / published_or_final_version / Earth Sciences / Master / Master of Philosophy

The tropical Indo-Pacific is the location of highest global foraminiferal biodiversity. However, the shallow-water hydrothermal system in Tutum Bay at Ambitle Island, Papua New Guinea, possesses some of the world's highest naturally-occurring [As]. Foraminifers were collected in this intriguing system in 2003 and 2005 as part of a larger project to examine the possible effects of As and other hydrothermal factors on benthic communities. Despite the high ambient [As], a diverse foraminiferal fauna was observed. Foraminferal communities were examined from surface sediment and from material adhered to rubble at locations from 1-300m from venting and from reference sites, at depths from 1-28m. From this material, 159 species were identified representing 107 genera, 55 families, 30 superfamilies, and 10 orders. Species abundances exhibit a logarithmic series distribution, with two species comprising 40%, twelve species comprising two-thirds, and 20 species comprising 80% of all identified specimens. All other species individually contributed <1% to the total community. Foraminiferal abundance and diversity were analyzed across the hydrothermal field; both increase with decreasing hydrothermal influence: decreasing sediment and pore water [As] and temperature, and increasing pH and salinity. A thorough taxonomic reference of the region was compiled, consulting appropriate original descriptions, and is herein presented, and initial steps in creating an online database of all Recent foraminifers is described. Scanning electron micrographs of the most common taxa are provided. Laboratory experiments assessed the effects of [As³?] and [As5?] on growth of Amphistegina gibbosa. Exposure to As³? and As5? at concentrations of 0- 1000µg/kg showed that As³? is approximately 2.2 times more toxic than As5?, that [As³?] of 600- 1000µg/kg is sufficient to kill or severly impair specimens on approximately two-week timescales, and that [As5?] of 1000µg/kg or [As³?] of 200µg/kg are sufficient to retard the growth of A. gibbosa on approximately four-week timescales. Over timescales of several months, cultures with extremely low [As] (2µg/kg As5? and 0µg/kg As), showed growth rates not significantly greater than high-[As] treatments, possibly due to antimicrobial/parasiticidal properties of low [As]. Foraminifers displayed an exponentially-decaying functional relationship to [As], halving their rate of growth with every 300µg/kg increase in [As³?] or 600µg/kg increase in [As5?]. Measurements of foraminiferal whole-specimen [As] via SEM-EDX, AFS, and ICP-MS revealed high [As] of ~20mg/kg for specimens near hydrothermal venting declining to background values of ~2mg/kg for distal and non-hydrothermal reference species. Laboratory-exposed specimens contain [As] of ~6mg/kg indicating an As adsorption rate of ~0.25mg/kg/wk. The major portion of foraminiferal As likely occurs in a reduced-toxicity organoarsenical form, such as arsenobetaine.

Phytoremediation has been intensively studied during the past decade due to its cost-effectiveness and environmental harmonies. Most of the studies on treatment of heavy metal pollution in soil and water by plant species have been done in developed countries but are limited in Vietnam. In this study, we presented some research results of phytoremediation of polluted soils and water with heavy metals that were done by Institute of Environmental Technology for several last years. For treatment of heavy metal pollution in the water, some plants have great ability to accumulate heavy metals such as Vetiveria zizanioides, Phragmites australis, Eichhornia crassipes, Pistia stratiotes, Ipomoea aquatica, Nypa fruticans and Enhydra fluctuans. The heavy metal uptake into shoots and roots of 33 indigenous plant species in Thai Nguyen province was also determined. Two species of the plants investigated, Pteris vittata L. and Pityrogramma calomelanos L. were As hyperaccumulators, containing more than 0.1% As in their shoots while Eleusine indica, Cynodon dactylon, Cyperus rotundus and Equisetum ramosissimum accumulated very high Pb (0.15-0.65%) and Zn (0.22-1.56%) concentrations in their roots. Some experiments to clarify the potential of several plants as good candidates for phytoremediation of polluted soil by heavy metals were carried out in our institute. / Phương pháp sử dụng thực vật để xử lý ô nhiễm đã được nghiên cứu nhiều trong thập kỷ qua do chi phí thấp và thân thiện với môi trường. Hầu hết các nghiên cứu về xử lý ô nhiễm kim loại nặng trong đất và nước bằng thực vật đã được thực hiện ở các nước phát triển nhưng ít có tại Việt Nam. Trong nghiên cứu này, chúng tôi giới thiệu một số kết quả dùng công nghệ thực vật để xử lý ô nhiễm kim loại nặng trong đất và nước tại Viện Công nghệ môi trường trong những năm gần đây. Dối với xử lý ô nhiễm kim loại nặng trong nước, một số thực vật có khả năng tích lũy tốt kim loại nặng như Vetiveria zizanioides, Phragmites australis, Eichhornia crassipes, Pistia stratiotes, Ipomoea aquatica, Nypa fruticans và Enhydra fluctuans. Sự hấp thụ và tích lũy kim loại nặng trong phần trên mặt đất và rễ của 33 loài thực vật bản địa tại Thái Nguyên cũng đã được xác định. Hai loài thực vật khảo sát là Pteris vittata và Pityrogramma calomelanos là những loài siêu tích lũy As, chứa hơn 0,1% As trong phần trên mặt đất của cây. leusine indica, Cynodon dactylon, Cyperus rotundus và Equisetum ramosissimum tích lũy Pb (0,15-0,65%) và Zn (0,22-1,56%) rất cao trong rễ. Một số thí nghiệm đánh giá tiềm năng của một số thực vật là đối tượng tốt cho xử lý ô nhiễm kim loại nặng trong đất đã được tiến hành trong phòng thí nghiệm của Viện Công nghệ môi trường.

M. Tech. Chemical Engineering / The lack of clean and fresh water has become a worldwide problem because of water pollution caused by industrialization. Contamination of natural water sources by heavy metal is a worldwide public health problem, leading to waterborne outbreaks of infectious hepatitis, viral gastroenteritis, and cancer. Therefore it very important to remove these toxic metal ions from municipal and industrial effluents in order to protect plants, animals and human beings from their adverse effect before discharging into natural water bodies. Although, several separation methods such as filtration, reverse osmosis and membrane technology have been developed to remove these toxic heavy metal ions from wastewater, however these conventional treatments technologies were found to be expensive on a sustainable basis. Adsorption process was identified as the most effective, and extensively used essential process in wastewater treatment, and in order for adsorption process to feasibly remove pollutants from wastewater, there should be a need for a suitable adsorbent which will have a large porous surface area, and a controllable porous structure. Through the application of nanotechnology, nano adsorbents can be developed as effective adsorbents to treat wastewater. The main objective of this project was to apply magnetic metal doped iron oxides as an efficient adsorption media for the removing of Cr(VI), Cd(II) and V(V) ions from wastewater.

M. Tech. Chemical Engineering. / In this study, nano-structure hydrotalcite material was used as an adsorbent for the removal of heavy metals of lead (Pb), nickel (Ni), cadmium (Cd) and cobalt (Co) from wastewater. It was observed that, in comparison with single component system (Ni, Cd and Co only), the presence of co-ions reduced the Ni (II), Cd (II) and Co (II) adsorption suggesting suppression of the desired ion by the presence of co-existing ions. The kinetic data fitted well to pseudo-second order model while the equilibrium data were satisfactorily described by Langmuir isotherm. The adsorption capacities of Ni (II), Cd (II) and Co (II) at pH 6.0 were found to be 142.8, 200 and 142.8 mg/g at 25oC.

M. Tech. Environmental Management / Investigates the possibility of using maize tassel powder as a solid phase extraction sorbent for the recovery of Ag, Au and Cu from aqueous solution. The surface characteristics of maize tassel and its ability to remove Ag, Au and Cu from aqueous solutions needed to be established before the preparation of maize tassel beads.

Thesis (MTech. degree in Environmental management.)-Tshwane University of Technology, 2008. / Aims to generate information on the quality of water from boreholes and the Steelpoort river in order to ascertain the level of pollution within the vicinity of Vantech mine. The information is envisaged to help a better water management within the area. The following objectives were pursued: to measure water quality parameters ; to investigate the extent of the pollution plume movement ; to study the composition and geological factors in the area in relation to mobility of groundwater and to determine the impacts of Geo hydrological characteristics.