Removal of Heavy Metal from Wastewater

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Removal of Heavy Metal from Wastewater. An Alternative Green Sonochemical Process Optimization and Pathway Studies. Nalenthiran Pugazhenthiran ...

Removal of Heavy Metal from Wastewater An Alternative Green Sonochemical Process Optimization and Pathway Studies Nalenthiran Pugazhenthiran, Sambandam Anandan, and Muthupandian Ashokkumar

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Conventional Technology for the Removal of Heavy Metal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Activated Carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Chemical Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Chemical Oxidation and Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Membrane Separation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Ion Exchange . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Ultrasonic Removal of Heavy Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Abstract

The development of environmental remediation technologies targets to minimize the toxic effects of pollutants. Among developing remediation technologies, sonochemistry is an emerging technology for the removal of pollutants in aqueous environment. Primary reaction generated during acoustic cavitation is the homolytic cleavage of water molecules into atomic hydrogen (H) and hydroxyl (OH) radicals. Hydroxyl radicals unselectively oxidize target pollutant molecules. This chapter deals with technical feasibility of sonochemical process for the removal of heavy metal pollutants from aqueous environment. The removal of heavy metal pollutants using adsorption materials in the presence of ultrasonic N. Pugazhenthiran • S. Anandan (*) Nanomaterials & Solar Energy Conversion Lab, Department of Chemistry, National Institute of Technology, Trichy, India e-mail: [email protected]; [email protected] M. Ashokkumar School of Chemistry, University of Melbourne, Parkville, VIC, Australia e-mail: [email protected] # Springer Science+Business Media Singapore 2015 M. Ashokkumar (ed.), Handbook of Ultrasonics and Sonochemistry, DOI 10.1007/978-981-287-470-2_58-1

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irradiation shows better efficiency compared to reactions in the absence of ultrasonic irradiation. It is concluded that ultrasonic technology is a simple and possibly cost-effective alternative for the oxidation of heavy metals with and without assistance of external catalysts. Keywords

Activated carbon • Cadmium emission • Heavy metal removal • By sonochemical • Conventional technology • From inorganic effluent • Ion exchange • Membrane separation methods • Ultrasound-assisted sorption processes • Ultrasonic removal • United State Environmental Protection Agency (USEPA) maximum contamination levels

Introduction The term “heavy metals” refers to any metallic element that has a relatively high density and is toxic or poisonous even at low concentrations. “Heavy metals” is a general collective term, which applies to a group of metals and metalloids with atomic density greater than 4 g cm3 [1]. Although several adverse health effects of heavy metals have been known for a long time, exposure to heavy metals continues and is even increasing in some parts of the world. Heavy metals include lead (Pb), cadmium (Cd), zinc (Zn), mercury (Hg), arsenic (As), silver (Ag), chromium (Cr), copper (Cu), and iron (Fe) [2]. Emission of heavy metals to the environment occurs via a wide range of processes and pathways contaminating air (e.g., during combustion, extraction, and processing), water (via runoff and releases from storage and transport), and soil [2, 3]. Atmospheric contamination tends to be of greatest concern in terms of human health [3–5]. Lead emission is mainly related to road transport and thus most uniformly distributed throughout the atmosphere [2, 5]. Cadmium emission is primarily associated with nonferrous metallurgy and fuel combustion, whereas the spatial distribution of anthropogenic mercury emissions reflects the level of coal consumption in different regions [2, 5]. Moreover, discharge of heavy metal wastes into effluent over the past few decades has inevitably resulted in an increased flux of metallic substances into the global aquatic environment due to their acute toxicity, nonbiodegradability, and buildup in high concentrations [6]. Point and nonpoint source industrial runoffs from battery manufacturing, printing and pigments, tanneries, oil refining, mining smelting, electroplating, paintings, and most recently e-wastes have resulted in elevated levels and chronic toxicity of lead (Pb2+), cadmium (Cd2+), copper (Cu2+), and iron (Fe2+). Consequently, these heavy metals have been extensively studied and their effects on human health regularly reviewed by international bodies such as the WHO [2, 6]. The maximum permissible limit of these heavy metal ions (Pb2+, Cd2+, Cu2+, and Fe2+) in inland surface water and drinking water are 0.006, 0.01, 0.25, and 0.1 mg L1, respectively, according to the United State Environmental Protection Agency (USEPA) (Table 1) [7].

Removal of Heavy Metal from Wastewater

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Table 1 United State Environmental Protection Agency (USEPA) maximum contamination levels for heavy metal concentration in air, soil, and water [7]

Heavy metal Cd Pb Zn2 Hg Ca Ag As

Maximum concentration in air (mg m3) 0.1–0.2 . . ... 1, 5a . . ... 5 0.01 . . ...

Maximum concentration in sludge (soil) (mg/Kg or ppm) 85 420 7,500 50 0.1 . . ...

Value in bracket is the desirable limit 1 for chlorine fume, 5 for oxide fume; . . . no guideline available b WHO; EPA, July 1992 c USEPA, 1987 a

Especially, wastes produced from the industrial activities not only bring about serious environmental effect but also threaten human health and ecosystem [5]. These heavy metals, for the convenience of analysis, reportedly fall into three families: toxic metals (Hg, Cr, Pb, Zn, Cu, Ni, Cd, As, Co, Sn, etc.), precious metals (Pd, Pt, Ag, Au, Ru, etc.), and radionuclides (U, Th, Ra, Am, etc.) [2, 3, 5, 8]. The methods for removing heavy metal ions from aqueous solution mainly consist of physical, chemical, and biological processes. Traditional physiochemical methods include chemical precipitation, oxidation or reduction, filtration, ion exchange, electrochemical treatment, reverse osmosis, membrane technology, and evaporation recovery [9–13]. Most of these are ineffective or excessively expensive when the metal concentrations are

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