Elsevier

Water Research

Volume 38, Issue 17, October 2004, Pages 3780-3790
Water Research

Removal of arsenic using hardened paste of Portland cement: batch adsorption and column study

https://doi.org/10.1016/j.watres.2004.06.018Get rights and content

Abstract

Hardened paste of Portland cement (HPPC) has been used as a low-cost adsorbent for the removal of arsenic from water environment. Results from the batch experiments, conducted at an initial concentration of 0.2 ppm of arsenate, suggest arsenate removal up to 95%. Kinetic profiles were developed for various conditions. Effects of adsorbent dose, common ions such as Ca2+, Mg2+, Fe3+, Fe2+, Cl, SO42−, NO3, PO43− and of pH were studied in detail. Adsorption isotherm studies revealed that the Freundlich isotherm was followed with a better correlation than the Langmuir isotherm. Arsenite could also be removed up to ∼88% using the same material, HPPC. Finally, column studies were undertaken involving the new HPPC to check the suitability of the material for the removal of total arsenic content from water body. Kinetic experiments for the removal of arsenic by column studies revealed a film diffusion mechanism.

Introduction

Today, millions of people in the world are suffering from arsenic related diseases due to consumption of arsenic contaminated underground water. Arsenic pollution in ground water has been found in many countries in different parts of the world. High concentration of arsenic in water has caused symptoms of chronic arsenic poisoning in local populations of many countries like India (Das et al., 1994; Chatterjee et al., 1995), Bangladesh, Taiwan (Shen, 1973; Hricko, 1994), Mongolia, China (Hricko, 1994; Niu et al., 1995), Japan, Poland, Hungary, Belgium, Chile, Argentina and North Mexico. The arsenic polluted areas of the world can be geologically subdivided into areas made of sediments derived from water or volcanic rocks characterized by the presence of geysers, gold and uranium mining areas. These elevated arsenic concentrations are mostly of natural origin. Arsenic is a contaminant in ground water because of the same reason. In areas with current or historical mining activities, however, arsenic contamination of natural water may be associated with leaching of mine tailings or deposition of arsenic released to the atmosphere during smelting process as has occurred in southern Thailand, Ghana (Bowell et al., 1994) and the western United States (Benner et al., 1995). Mitigation of arsenic exposure in such areas primarily involves substitution of drinking water from alternative (uncontaminated) sources, or treatment of source waters containing arsenic well in excess of the current standards. The current standard or maximum contaminant level (MCL) in the United States is 10 μg L−1 (10 ppb); the provisional guideline value recommended by the World Health Organization is 10 μg L−1 (WHO, 1993; Pontius, 1993). In the United States, uses of source waters containing arsenic concentration significantly above the current MCL and consequent exposure of local population to such elevated levels of arsenic in drinking water are rare. Isolated incidents have been reported including a case of acute arsenic poisoning in the state of Washington (Frost et al., 1993). A reduction of the arsenic MCL to a value in the range of 2–10 μg L−1 is currently under consideration by the US Environmental Protection Agency (Pontius, 1993).

Arsenite is about 60 times more poisonous than arsenate and 70 times more toxic than the methylated species (Ferguson and Davis, 1972; Cullen and Reimer, 1989; Korte and Fernando, 1991). Manifestation of higher doses of inorganic arsenic compounds in the human body leads to the disease called arsenocosis. Arsenic contamination is of mostly geogenic origin and is known for its high toxicity and its ability to induce skin cancer on long-term ingestion. On this background some research on the evaluation of treatment methods has been done. Any treatment of arsenic contaminated water requires methods of detection and decontamination, i.e., removal of arsenic from water, which can span a wide range of concentrations. Although cited references of both the processes (detection and removal) well summarized the chemistry at hand, additional efforts are required for real-time application of these principles. Detection procedures/kits that are usually employed vary from the age-old Marsh test to ion-associate formation (Pal et al., 1995, Pal et al., 1996), atomic absorption spectroscopy (AAS) (Grabinski, 1981), neutron activation analysis (NAA) (Steinnes, 1975) etc. depending on the gravity and need of the situation. Great number of scientists have put forward their efforts to alleviate the problem of arsenic removal from water body. A number of treatment options are available with demonstrated efficiency for arsenic removal at least to the level of the current MCL. Such treatment technologies include coagulation (Shen, 1973; Sorg and Logsdon, 1978; Hsia et al., 1994; Cheng et al., 1994; Edwards, 1994; Scott et al., 1995), softening (McNeill and Edwards, 1995), adsorption on alumina (Belleck, 1971; Gupta and Chen, 1978; Ghosh and Yuan, 1987; Hathaway and Rubel, 1987; Xu et al., 1991; Yodnane et al., 1992), or activated carbon (Gupta and Chen, 1978; Huang and Fu, 1984), anion exchange (Clifford, 1990; Ramana and Sengupta, 1992) and reverse osmosis (RO) (Fox and Sorg, 1987; Fox, 1989). The choice of a suitable treatment option for a specific water supply scheme will depend on a number of factors including the mandated arsenic concentration, the existing treatment system and the extent to which it can be modified to optimize for arsenic removal and other water quality parameters that must be met along with the arsenic standard.

In general, coagulation technique (Shen, 1975; Sorg and Logsdon, 1978; Hsia et al., 1994; Cheng et al., 1994; Edwards, 1994; Scott et al., 1995) is not cost effective and less efficient for As(III) removal. RO (Fox and Sorg, 1987; Fox, 1989) process removes As(V) more effectively. Again, ion exchange (Clifford, 1990; Ramana and Sengupta, 1992) and adsorption on activated alumina (Belleck, 1971; Gupta and Chen, 1978; Ghosh and Yuan, 1987; Hathaway and Rubel, 1987; Xu et al., 1991; Yodnane et al., 1992) have been found to be the best suited techniques for the removal of As(V) than As(III), because As(V) is generally present as an anion in the medium-pH range while As(III) exists as uncharged molecules in water. The most common technique is the removal of arsenic on the precipitation of ferric arsenate FeAsO4.2H2O over the temperature range of 25–110 °C (Robins, 1985) followed by filtration. This technique allows residual arsenic concentrations below 10 μg L−1 and the dose of ferric salts below 10 mg L−1 (Cheng, 1994). Studies were made at the University of Burgas (Department of Water Technology) to examine the efficiency of Fe(III)–As system to decontaminate the lake Topolniza in Bulgaria, which was polluted due to a copper production plant situated in the upper part of the river Topolniza (Nenov et al., 1994). Recently, Le Zeng reported the use of granulated iron(III)-based binary oxide adsorbent for As removal (Zeng, 2003) through column adsorption process. Another more simple but less effective technique involves adsorption of arsenic on activated alumina in fixed bed reactor (Rosenblum and Clifford, 1984). The typical capacity of this fixed bed reactor is 3000–10,000 bed volume with respect to a tolerable effluent arsenic level of 10 μg L−1. The residual mass of spent adsorbent is in the range of 50–200 g m−3 treated water, this is nearly ten times more than the amount of coagulant sludge from the coagulant with ferric salts.

The requirements for a removal technique of arsenic from drinking water are the safe operation with respect to the maximum contaminant level, effectiveness, simple processing for application in small water facilities and minimal residual mass of arsenic contaminated waste.

We have developed a simple, cost effective arsenic removal technique using a commercially available Fe–Al–Si–O2 containing complex material (hardened paste of Portland cement (HPPC), L&T, India). The chief constituents of the cement are SiO2 (21%), CaO (63%), Al2O3 (7%), Fe2O3 (3%), MgO (1.5%) along with other trace constituents. Under the same experimental condition, the removal efficiency involving HPPC was compared with other materials such as activated charcoal and brick bat granules (Table 1). The comparison has been made with the adsorbents like activated charcoal and brickbat granules (Table 1). It has been found that HPPC is the best among them. The adsorbent has been successfully applied for arsenic removal from three water samples collected from arsenic contaminated tube wells of different parts of arsenic-affected regions of Eastern India (West Bengal). Different important parameters like adsorption isotherm, efficiency and regeneration of the adsorbent have been studied. A recently developed method (Kundu et al., 2002) has been used for the quantification of arsenic. Batch and column operations involving HPPC as the adsorbent successfully removed >90% arsenic (total) from the local well-water samples containing ppb levels of arsenic (Pal et al., 1996).

Section snippets

Instrumental

A digital pH meter (ECL, Government of India) was used for pH measurement. A mechanical shaker was used for shaking all the solutions. All absorbance measurements were carried out with Shimadzu (Kyoto, Japan) UV-160 digital spectrophotometer equipped with 1-cm quartz cuvette. For column studies a Masterflex peristaltic pump was used to feed solutions into the columns (Sigma, borosilicate glass).

Reagents

All reagents were of analytical grade. Methylene blue (MB) (Fine Chemicals, India) was purified by

Micellar catalysis

The quantitative colour bleaching of MB (Ghosh et al., 2002) by Arsine (AsH3) has been studied in micelle. This colour bleaching of MB was found to be spontaneous in SDS micelle. This can be explained with the concept of encounter probability (Pal et al., 1998) and fractal nature of the micellar surface (Blumen et al., 1986). In this case, MB being a cationic dye, is bound to SDS (Ghosh et al., 2002) by both electrostatic as well as hydrophobic interactions (Pal and Jana, 1996). The

Conclusions

Hardened paste of Portland cement has been shown to be an effective adsorbent for arsenic removal. In view of the study reported here it appears possible to remove arsenic (if present as arsenate) almost quantitatively (>95%) from drinking water. The adsorption isotherm follows Freundlich isotherm model better than the Langmuir isotherm. Reasonable quantity of sulfate, phosphate and lower amount of chloride do not affect arsenic removal. Other positive and negative ion viz., ferrous/ferric,

Acknowledgements

S. Kundu and S.K. Ghosh are grateful to the Department of Science and Technology (DST), New Delhi for financial support and M. Mandal thanks Council of Scientific and Industrial Research (CSIR), New Delhi for financial assistance.

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