1997; Le, 2002). Although beneficial effects have been reported for some arsenic compounds e.g. reduction of fever, prevention of black-death, healing of boils, and treatment of chronic myelocytic leukaemia (Goessler and Kuehnelt, 2002), the adverse health effects of arsenic are much more common. While acute arsenic poisoning can lead to rapid death, chronic negative health impacts are more common and tend to appear only after several years of exposure (Hanchett et al., 2002). The most commonly observed symptoms identifying people suffering from chronic arsenic poisoning are arsenical skin lesions (e.g. melanosis, keratosis), blackfoot disease, and in more serious cases, incidents of gangrene, skin cancer (when ingested), and lung cancers (when inhaled) (Das et al., 1995; Karim, 2000; Hanchett et al., 2002). It is noted, however, that no clear correlation between arsenic concentrations in water and skin cancer has been reported in the USA (see Valberg et al., 1998) suggesting that other factors may affect the link between arsenic intake and skin cancer; e.g. dietary factors (Das et al., 1995). It is important to note that the most effective way to overcome the adverse health effects of arsenic is prevention of further exposure by providing safe drinking water, because there is no effective treatment to counteract arsenic toxicity. Therefore, the World Health Organization (WHO, 1993) has recommended a maximum contaminant level (MCL) for drinking waters of 0.01 mg/L. Many countries however, permit higher arsenic concentrations in drinking water mainly due to the high cost of treatment to lower concentrations. As noted by Gregor (2001) the MCL value is the concentration below which the presence of arsenic is not considered to pose a significant health risk, even after a lifetime consumption of the water. Hence, when setting an MCL it is necessary to better understand and balance the health risks associated with drinking arsenic bearing water against alternative sources of water, the cost and practicality of the treatment and the practical limitations of analytical methods (Waypa et al., 1997). The treatment of arsenicfrom drinking water has attracted growing interest due to the negative health effects of drinking arsenic contaminated water as noted above, and to the fact that more stringent standards have been introduced for arsenic in many countries e.g. in the USA and the EU the allowable limit has been reduced from 0.05 mg/L to 0.01 mg/L (Council Directive, 1998; US EPA, 2001). As a result, a lot of research has been carried out with the specific aim of developing cost-effective arsenicremoval techniques. Several removal methods have been proposed and adsorption has emerged as one of the most practical methods because it can easily be used in small- scale systems and developing more efficient new adsorbents is possible; a wide range of cost-effective adsorbents are already available or may be developed.
These new regulations impose a demand for more ef- ficient arsenicremovalfrom drinking water. Among conventional arsenicremoval technologies mainly utiliz- ing adsorption and coagulation processes, membrane processes have emerged as a promising new route for high quality water purification. These approaches have many advantages, including no requirement for the addi- tion of chemical substances, easy increase of capacity, separation in the continuous mode and the possibility to easily join membrane processes with other unit processes [6-9]. Arsenicremoval pressure-driven membranes are mainly based on reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF) or microfiltration (MF) [10-12].
This study examines the potential of removing arsenicfromwater by coprecipitation with naturally occurring iron. The experimental study examined the sensitivity of removal of arsenic in response to manual mixing and prolonged settlement. It was found that about 88% arsenicremoval could be achieved after 24 h settlement. It has also demonstrated that provided the iron levels are sufficiently high (say 1.2 mg/l), simple shaking of a container and allowing the iron-arsenic complex to settle out for 3 days could reduce the concentration of arsenicfrom 0.10 mg/l to Bangladesh standard (0.05 mg/l). There was evidence that adsorption may be the dominating trapping mechanism when Fe/As weight ratio was ≥ 10.
treatment and disposal of the resulting waste sludge. Bioconversion and photochemical oxidation of As(III) need another units to remove As(V). Adsorption process remains ineffective in low concentration and needs pre oxidation of As(III) to As(V) for effective removal. Furthermore, frequent regeneration of adsorbent and disposal of spent adsorbent are the other disadvantages with adsorption process. Disposal of arsenic containing sludge produced in electrocoagulation process generates a new problem. In addition, it requires air injection, high voltage (40 V) and high current (4A) for effective performance of electrocoagulation process . Reverse osmosis, membrane filtration and ion exchange processes have high arsenicremoval efficiency that can lower down arsenic concentration in treated water as low as 2-5 μg/L . In electrochemical ion exchange (EIX) process an electric potential in place of chemical reagents is used to elute ion exchange media . In this paper, comparisons on the efficiency of ion exchange, electro membrane and EIX methods on arsenicremoval have been made.
mining and metallurgy of non-ferrous metals . Con- tamination of drinking water (groundwater) arises fromarsenic-rich rocks . At present, different media such as granular ferric hydroxide, activated alumina, etc. is used for the removal of arsenicfrom drinking water. The dis- posal of the sludge from As filter media has become a great concern for the environmental scientists. Once the sludge is disposed of into the soil, it may act as a source of soil contamination with arsenic and other toxic ele- ments . The release of arsenicfromarsenicremovalwater filter sludge could enhance arsenic bioavailability to plants due to mobilization of As into the soil solution. Therefore, the objective of this study was to investigate the extent of arsenic release fromarsenicremovalwater filter sludge and its uptake by amaranth plant.
application was investigated for arsenicremovalfromwater. Characterization of the nano sized adsorbent particles was carried out using SEM and XRD techniques. Systemic adsorption experiments were performed in batch systems and the optimum conditions were obtained. The effects of pH, contact time, adsorbent mass, temperature, ionic strength and initial concentration of arsenic were investigated on kinetics and equilibrium of the adsorption. Thermodynamic parameters and adsorption kinetics were studied in detailed to know the nature and mechanism of adsorption. Kinetic studies showed that the adsorption process followed pseudo second order kinetic model. The thermodynamic parameters such as ΔG ⁰ , ΔS ⁰ and ΔH ⁰ were calculated, and it was found that the reaction was spontaneous and exothermic in nature. Adsorption equilibrium was studied using Langmuir and Freundlich isotherm models. It was observed that the investigated adsorption process followed Freundlich isotherm. Adsorption capacity (q0) calculated from Langmuir isotherm was found to be 8.260 mg.g-1.The results showed that CeO 2 /Fe2O3 nanocomposite particles can be effectively used for the removal of As(III) ions from
Scanning electron microscopy (SEM) images were obtained by Hitachi TM3030 (Japan) and the elemental contents were analyzed by energy dispersive X-ray spectroscopy (EDS). X-ray diffraction (XRD) patterns were obtained by Philips PW automated X-ray powder dif- fractometer (USA). The specific surface area was obtained by nitrogen adsorption using the Brunauer–Emmett–Teller (BET) method and the mesopore and micropore volumes were det- ermined using the BJH and t-test methods, using a Quantachrome autosorb TMiQ surface area analyzer. The point of zero charge (pH pzc ) was determined according to the method described
Although humans can be exposed to arsenic through different pathways like air, food or soil, arsenic conta- minated drinking water represents the major threat of all arsenic sources to human health, contributing mainly to the incidence of Chronic Endemic Regional Hydroarsenicism . Toxicity of arsenic depends on the form it is found in nature; it can be present in different oxidation states ( −3 Arsine, +1 Arsonium Metals, +3 Arsenites, +5 Arsenates, 0 Elemental Arsenic)  . Those compounds with +3 oxidation state are more toxic than com- pounds with +5 oxidation state, and inorganic arsenic compounds show higher toxicity than organic ones . Arsenic organic compounds are found in food and marine organisms while inorganic arsenic compounds are found in minerals and in many aquifers, where they accumulate by means of natural processes . In several re- gions of the world, aquifer water is used for drinking purposes. It represents an increased risk to develop serious diseases  ; since soluble arsenic compounds are extremely toxic  .
Arsenic contamination in natural water is a worldwide problem because of its known toxicity and health hazards. The US Environmental Protection Agency (USEPA) has classified arsenic as a Class ‘A’ human carcinogenic and because of the serious health problems caused by arsenic in 2001, it reduced the maximum arsenic content in drinking waterfrom 50 ppb to10 ppb. Thus several technologies such as oxidation and filtration , A wide range of physical and chemical treatment methods have been applied for arsenicremovalfrom contaminated waters fall into the following categories: (a) precipitation–coagulation processes, such as coagulation with iron or aluminum salts or Lime softening (b) membrane processes, such as reverse osmosis, ultrafiltration, Nano filtration, and electro dialysis. (c) adsorption processes, such as adsorption on activated or modified materials (d) ion exchange . In these methods, the adsorption techniques are simple and convenient and easily available and have the potential for regeneration and sludge-free operation. Various adsorbents for arsenicremoval have been developed that include such materials as activated carbon, agricultural products and by-products e.g. waste rice husk , eggshell  and shrimp shell , industrial by- products/wastes e.g. fly ash  and redmud ), oxides e.g. iron oxide , manganese oxides  and alumina , bio sorbents [13,14]
A liquid and/or solid residual may be produced from an AA system depending on the type of operation. If the system is regenerated, a liquid waste is produced from the backwash, caustic regeneration, neutralization, and rinse steps. In some instances, sludge may be generated from the regeneration and neutralization streams because some alumina dissolves during the regeneration step and may be precipitated as aluminium hydroxide . If aluminium based sludge is produced because of lowering the pH of the liquid residual, this sludge will contain a high amount of arsenic because of its arsenic adsorption characteristics. This sludge and the remaining liquid fraction of the solution will require disposal . Because both residuals contain arsenic, their disposal may be subject to disposal requirements. When the AA has reached the end of its useful life, the media itself will also become a solid residual that must be disposed . Because of its high arsenicremoval capacity, an activated alumina system may be operated on a media throwaway basis rather than a media regeneration basis. When operated on a throw-away basis, the exhausted AA media will be the principal residual produced. This media has the potential of being classified as a hazardous waste because of its high arsenic content. A TCLP (Toxicity Characteristic Leaching Procedure) test is necessary, therefore, to determine its classification and ultimate disposal restrictions . Because the AA media will filter out particulate material in the source water, the media bed will occasionally require backwashing. This backwash water will likely contain some arsenic attached to either the particulate material or the very fine AA material that is removed during backwashing. Consequently, the disposal of the backwash water may also be subject to the disposal requirements [101,102].
97% supplied by Chemical Products, Monterrey) and deionized water with conductivity of 0.95 μS cm −1 (Al- drich Chemical Co. 99.5%). The solutions and solids were then separated by filtration through cellulose filter paper. The sludge from the EC was dried either in an oven or under vacuum at room temperature. The experi- mental set-up is presented in Figure 2. The current and voltage during the EC process were measured and rec- orded, using Cen-Tech multimeters. The pH values of the solution before and after EC were measured with a VWR scientific 8005 pH meter.
In spite of the severity of the groundwater arsenic pollution problem, unfortunately there is presently no perfect solution in the affected areas. Among the countermeasures recommended are in the following order: (1) piped surface water, (2) rainwater harvesting, (3) deep tube well water, (4) dug well water, (5) shallow tube well water purified by a reliable and sustainable arsenicremoval technology . However, as described in section 1, residents in the areas have no choice but to use, or partially use, tube well water for their daily life and/or irrigation of crop land. Therefore, the establishment of arsenicremoval systems in these areas must have the highest priority. Arsenicremoval systems for daily use water and irrigation water can be considered separately. The water quality for daily use must consistently meet WHO drinking water standards, and the desired removal style is set up for larger communities so that maintenance and reliability issues can be addressed. On the other hand, arsenicremoval systems for irrigation water can be individual or group maintained, depending on the area of crop land and distance to the tube
DOI: 10.4236/ajac.2018.97027 341 American Journal of Analytical Chemistry aroused attention due to groundwater levels in many parts of the world at much higher concentrations than the maximum contaminant level of 10 μg/L for ar- senic in drinking water. Many problems of health fromarsenic contained in drinking water have been observed in Bangladesh , in Vietnam  in Cambo- dia  and Burkina Faso . In Akouédo (Côte d’Ivoire), high Arsenic concen- trations in drinking waterfrom well have been recorded in our previous work . In fact, in this area, well water is the main source of drinking water supply. So, the presence of the arsenic in these underground waters will cause problems. Thus, several conventional processes for treatment of arsenic like coagula- tion-flocculation , co-precipitation , ion-exchange  and nanofiltration process  have been reported. However, these processes involve production of high arsenic contaminated sludge , high maintenance cost and require rela- tively expensive mineral materials . Therefore, an effective arsenicremoval technology is thus highly desirable to provide safe drinking water to the affected people. Adsorption is gaining importance in recent days due to its technical simplicity and easier applicability in developing countries. This research work aims at removing arsenicfrom aqueous solutions by the geo-materials like late- rite, sandstone and shale. The specific objectives are 1) to determine optimal dose, the kinetic parameter of arsenic (III) adsorption, and 2) to study the effect of pH, time, and initial concentration on the arsenic (III) adsorption.
iron hydroxide). The results indicate that initial iron content of between 130 and 160 [µg / L] decreased to less than 20 [µg / L]. The conductivity slightly decreases by 10%. Expressed in carbonate hardness increased slightly by 5 to 7%. In all tests arsenicremoval was passed a flow of water through the bed to detect the presence of arsenic content of 10 [µg / L]. The initial silica content between 59 and 60.5 [mg / L] were significantly reduced. Initial although not relevant (0.25 [mg / L]), phosphates were not detected in the outlet water. In the plant operation with initial content of 65 [µg / L] has exceeded 10 [µg / L] in treated water after
In 1978 Sorg and Logsdon  first started to study the arsenicremoval technologies, like coagulation, lime softening, ion exchange, adsorption, reverse osmosis and electrodialysis. Jekel  continues their work by testing oxidation processes and activated alumina. Kartinen and Martin  found good results on arsenicremoval by using green sand and they also systematically arrange different treatment technologies into catego- ries. UV rays and ozone were introduced for arsenicremoval by Kuhl- meier and Sherwood in 1996 . Rott and Friedle  demonstrated in 1999 how to remove arsenic by adsorption onto fresh Fe(OH) 3 precipi- tatation if the water contains iron and manganese. There are a number of technologies used for removing arsenic . It is very important to establish the form in which arsenic is present in water, because the
the following effects, increasing proportionally to the amount of redmud added: 1) increase in pH, 2) increase in aqueous DOC concentrations, 3.) increase in aqueous metal(loid)s concentrations, and 4) increase in salinity (TDS). The redmud suspension released on the 4 th October 2010 was highly alkaline (pH 13), contained elevated concentrations of potentially soluble trace elements such as Al As Mo and V, and was highly saline (Klebercz et al. 2012; Milacic et al. 2012); therefore, the results observed in these experiments are to some extent expected. Soil specific behaviour, however, was observed. One of the soils tested (Soil H2) more effectively buffered the alkalinity added with the redmud, possibly due to the higher organic carbon content of this soil. This resulted in more modest increases in pH and trace element concentrations in experiments using soil H2 compared to those using soil H1 and H3. Interestingly, the higher pH buffering capacity observed for soil H2 was very similar to that of the single Hungarian soil sample used by Ruyters et al (2011) who also reported relatively small pH increases and no significant increase in trace metal concentrations in experiments using soil / redmud mixtures (up to 17% w/w redmud). In the present study significant increases in pH and trace element concentration were observed at redmud loadings less than 10% w/w using two of the three soils studied.
Thus the aim of this work was to use redmud as an absorbent to remove nitrogen and phosphorous from wastewater of petrochemical industry. The objective of this research is to investigate the potential of redmud for nitrogen and phosphorus removal in petrochemical industry wastewater. In order to achieve the objective of this work, the following scopes were identified for investigation: type of adsorbent treatment- raw, heat-treated, acid-treated, effect of adsorbent dosages of redmud on the performance of the phosphorus and nitrogen removal at 1 g/L, 3 g/L and 5 g/L, investigate effect of adsorbent sizes on the removal of phosphorus and nitrogen at 63 µm, 125 µm and 180 µm, effect of rotational speed at 0 rpm and 125 rpm on the performance of the nutrient removal, and investigate the effect of contact time from 0 to 150 min on the removal of nutrients.
In recent studies, plant wastes are inexpensive and they have no or very low economic value. In the present study activated carbon was prepared from cheap adsorbent as a new adsorbent for the removal of cresol red and basic fuchsine dyes from aqueous solutions. The effect of different parameters such as pH, adsorbent dosage, initial dye Abstract: An experimental investigation on the removal of cresol red and basic fuchsine dyes from waste water by using Albizzia lebbeck seed activated carbon (ALS AC) as low cost (cheap) adsorbent was carried out in a laboratory. Batch type experiments were conducted to study the influence of different parameter such as pH, adsorbent dosage, initial dye concentration, contact time and temperature of adsorbent. The removal data have been analyzed using Langmuir and Freundlich isotherm models. The kinetic data were used from the pseudo first order, pseudo second order and intra particle diffusion model and thermodynamic studies. The adsorption processes was in conformity demonstrated use of ALS to obtain low cost adsorbent for dye removalfrom aqueous solutions. The present investigation confirmed that ALS AC can be successfully employed as a good adsorbent for the removal of dye from effluent.
Seawater contains a variety of salts, and when evaporated, these solids are left behind. Layers of salt occur naturally in the geologic record, compromising an abundant source of salt for human consumption worldwide. Today, some salt deposits are land derived as when salty water seeps from rock, evaporates and leaves a salty residue. Human beings have been aware of deposit of rock salt for centuries, and when salt was still quite rare, wars were sometimes waged over the control of such deposits, because salt is so critical to many human activities 1 . Salt was controlled by governments and taxed as far back as 20 th century in China 2 . By the middle ages, caravans consisting as many as forty thousand camels traversed four hundred miles of the Sahara barring salt, sometimes trading it for slaves while other communities enriched themselves by trading salt and salted meats in the form of “trade by barter” for wine and other luxuries. Crystallization which is one of the most pristine unit processes has been thoroughly studied in more recent times by chemical industries so as to acquire more
The present work shows that thermally activated acid neutralized redmud can be used as adsorbent for the re- moval of hexavalent chromium from aqueous solutions successfully. SEM image indicated clearly the structural transformation of the RM after modified. The XRD and XRF studies revealed that RM contains significantly more metal ions than ARM. All the characteristics analysis indicated the successful modification of RM. The ARM has shown good adsorptivity for hexavalent chromium. For the solution of 0.08 mg∙L −1 , the maximum