Batch Adsorption Process of Metals and Anions for Remediation of Contaminated Water

Deepak Gusain, Faizal Bux, Deepak Gusain, Faizal Bux

• Publisher: CRC Press
• Year: 2021
• Print ISBN:
  9780367436483
• eBook ISBN:
  9781000348347
• Topic: Technology & Engineering
• Subtopic: Environmental Science
• Index: Technology & Engineering

Adsorption is one of the method that is in use for remediation of contaminated water. The experimental factors affecting the batch mode of adsorption of various metals and inorganic anions are discussed in this book. The elemental contaminants have been categorized into four major categories i.e. major toxic elements; essential elements having toxicity on excessive exposure; miscellaneous elements having undetermined effects; non-toxic elements having trivial or unidentified significance. In addition, anions like nitrate, perchlorate and sulphate as water contaminants are considered. This unique volume fills a niche in the area of water treatment.

Key Features:

• Provides practitioners with the background they need to understand and apply batch adsorption processes to the purification of water
• Describes the actions of adsorption capacity or percentage removal with respect to factors affecting the adsorption process
• Excellent source of information for those working in the industry for remediation of metals and anions
• Discusses the current era of Anthropocene which is highly dependent on the anthropogenic mineral sources for its sustenance

1 Introduction

Deepak Gusain

Durban University of Technology

Shikha Dubey and Yogesh Chandra Sharma

IIT(BHU), Varanasi

Faizal Bux

Durban University of Technology

Contents

1.1 Introduction

1.2 Adsorption: A Brief History

1.3 Absorption

1.4 Adsorption Process

1.5 Water Treatment by Batch Adsorption Process

1.6 Scope and Outline of the Chapters

1.1 Introduction

The rapid pace of development, or industrialization, resulted in an increased demand for metals. The widespread use of metals leads to their presence in the pristine environment. Over time, the natural remediation by the environment was not quite sufficient to maintain the level of contaminants below the safety levels recommended by health and environment organizations. In addition, lack or high cost of alternatives leads to oxymoron conditions in the use of metal industries. The concentration of contaminants can also present due to geological reasons, as in the case of arsenic in Bangladesh and West Bengal (India) where the concentration of the arsenic was sufficient to act as a pollutant (Nordstrom 2002). One of the major areas where the contaminants are present for a significant period of time is the aquatic ecosystem.

Living organisms are highly dependent on the aquatic ecosystem for their life sustenance. Consumption of contaminants present in the aquatic ecosystem causes health effects for the living organisms. Contaminants like chromium, manganese, iron, cobalt, nickel, copper, zinc, arsenic, lead, mercury and cadmium are known to affect human health (Klaassen 2013). In particular, chromium, cadmium, nickel and arsenic are reported to be carcinogenic in nature (WHO 2017). In addition, chromium causes ulceration and perforation of nasal septum, allergies, proteinuria, hematuria and anuria (Wilbur et al. 2012). Arsenic causes hyperkeratosis, liver injury (IARC 2012), black foot disease (Yu et al. 2002) and interference in heme synthesis, with an increase in urinary porphyrin excretion (Ng et al. 2005). Cadmium causes renal injury, osteoporosis and cardiovascular disease (Faroon et al. 2012). Lead causes peripheral neuropathy, chronic nephropathy and hypertension (Goyer 1990), proximal tubular dysfunction and renal failure (Goyer 1989).

In addition to heavy metals, other inorganic pollutants like anions also have adverse health effects; for example, a high intake of fluoride leads to dental or skeletal fluorosis (Death et al. 2015; Choubisa 2012) and a high intake of nitrate leads to methemoglobinemia (Gilchrist et al. 2010).

The need to deal with the adverse effects of metals and inorganic contaminants and the inability of the natural process to maintain the concentration of contaminants below the safety levels, above which they act as pollutants, lead to the development of methods for the treatment of these pollutants. Water can be remediated with a number of processes like precipitation, ion exchange, reverse osmosis, nanofiltration, coagulation–flocculation, electrocoagulation and adsorption. These technologies have their own benefits and limitations. Limitations include sludge generation during precipitation and the coagulation–flocculation process (Fu and Wang 2011), inability to handle high metal ion concentrations in ion exchange processes (Barakat 2011), membrane fouling in reverse osmosis (Greenlee et al. 2009; Kurniawan et al. 2006) and high operational and maintenance cost in electrochemical methods (Fu and Wang 2011). Adsorption also has limitations like the absence of a universal adsorbent and variable adsorption capacity for different materials (Dubey et al. 2017). In spite of this, adsorption is known for its cost-effectiveness, energy efficiency and complete removal of pollutants even at trace levels from dilute solutions, which makes it an attractive process for the removal of contaminants.

1.2 Adsorption: A Brief History

Adsorption is a surface phenomenon where change in concentration of the adsorbate occurs as compared to surrounding phases or accumulation or increase in concentration occurs at the interface between phases such as liquid-gas, liquid-liquid, and solid–gas; and the case we are discussing in this chapter is solid-liquid interface (Dąbrowski 2001; Summers et al. 2011; Swenson and Stadie 2019).

Adsorption process was observed in 1773 and 1777 by Scheele and Fontana, respectively (Dąbrowski 2001; West 1945; Swenson and Stadie 2019) during uptake of gases by charcoal. This was followed by Lowitz in 1785 when charcoal used for decolorization of tartaric acid solution. The term adsorption was first coined by du Bois-Reymond and introduced into the literature by Kayser (Dąbrowski 2001; West 1945; Patel 2019). Later, adsorption found its application in industries like sugar refinery and in chromatography.

Adsorption also forms the basis of chromatography developed by Mikhail Semyonovich Tsvet (Dąbrowski 2001). In addition, surface science yielded Nobel laureates like Irving Langmuir in 1932 and Gerhard Ertl in 2007.

1.3 Absorption

The term absorption was proposed by McBain while monitoring the slower uptake of hydrogen by carbon (Dąbrowski 2001; Swenson and Stadie 2019; Tan 2014). He also proposed the term sorption in cases where adsorption and absorption are difficult to distinguish, which led to the use of other terms like sorbate, sorbent and sorptive rather than adsorbate, adsorbent and adsorptive, respectively (Dąbrowski 2001).

Absorption is a bulk, or volumetric, phenomenon rather than a surface phenomenon, and it is limited by the degree of solubility of the adsorbate. Adsorption of gas in liquid depends on its solubility, whereas adsorption of gas depends on the adsorption isotherm. In absorption, the absorbate or material or gases penetrate into the structure of the solid or liquid rather than remaining on the surface and are mostly controlled by diffusion (Tan 2014; Worch 2012e).

1.4 Adsorption Process

Adsorption process can be carried out in any of the following ways: batch adsorption, continuous fixed-bed adsorption, continuous-flow tank adsorption, continuous moving bed, continuous fluidized bed and pulsed bed. The two most commonly used adsorption procedures are the batch and continuous mode for the removal of contaminants from an aqueous medium. These two adsorption procedures can be distinguished from each other in many ways (Table 1.1).

TABLE 1.1
Merits and Demerits of Batch and Continuous Mode of Adsorption Process

	Batch Adsorption Process	Continuous Adsorption Process	References
1	Batch adsorption process is classified as a discontinuous process.	Column adsorption experiments are identified as continuous experiments.	Worch (2012c)
2	Low amounts of adsorbent dispersed in large volumes of liquid. So, bulk density has the characteristics of a mass concentration of the solid particles rather than that of a conventional density.	Adsorbent particles are arranged in an adsorbent bed. Consequently, the proportion of the void volume is much lower than in the case of a batch reactor. For fixed-bed absorbers, the term bed density is often used instead of bulk density.	Worch (2012a)
3	In batch adsorbers, the adsorbent is in contact with the adsorbate solution until equilibrium is reached. The batch adsorber design for single-solute adsorption is, therefore, very simple and requires only combining the material balance with the isotherm equation.	A comparable material balance equation can be used under the assumption that the contact time in the adsorbent is longer than the time needed for establishing the equilibrium.	Worch (2012c)
4	In batch reactors, to minimize the influence of film diffusion, higher stirring speed is a prerequisite. High stirring speed leads to an increase in the risk of destruction of adsorbent particles. This can lead to errors in the determination of mass transfer coefficients, due to their particle size dependence.	In column experiments, the solution flows through a fixed bed of adsorbent. High flow velocities avoid the influence of film diffusion. In column experiments, adsorbent particles are shielded by the destruction due to high velocity.	Worch (2012d)
5	The mass transfer driving force decreases along with the adsorption rate due to declining concentration in the reactor.	In a fixed-bed reactor, the adsorbent faces a high driving force over the whole process	Worch (2012b)
6	In a batch reactor, very low residual concentrations can be achieved only if very high adsorbent doses are applied.	In a fixed-bed reactor, the adsorbate will be totally removed until the breakthrough occurs.	Worch (2012b)

Batch adsorption: In this process, a fixed amount of the adsorbent (solid phase) and the adsorbate (liquid phase) is agitated in a closed vessel. The detailed description of the process is given below.

Batch adsorption process in most of the studies is conducted in an Erlenmeyer flask or reagent bottles. Agitation is carried out in a temperature-controlled water bath shaker or orbital shaker. First, a requisite amount of the adsorbent is weighed and put into the reagent bottle. The temperature of the adsorbate solution and the water bath should be the same to minimize any energy exchange due to temperature difference. Thin-walled bottles are more prone to energy transfer than thick-walled reagent bottles. The adsorbate solution setup at the requisite temperature is then poured into the reagent bottle containing the adsorbent. The solution is then stirred for the requisite time or until equilibrium time is achieved. The adsorbent is then separated from the aqueous solution by filtration or centrifugation process. The solution is then analyzed for adsorbate concentration. The adsorbent post adsorption can then be regenerated by desorbing agents for reuse. The detailed batch adsorption process is illustrated in Figure 1.1.

FIGURE 1.1 Illustration of batch adsorption process.

Data collected during batch adsorption were used to test the new ad...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Acknowledgement
• List of Abbreviations
• Editors
• Contributors
• Chapter 1 Introduction
• Chapter 2 Adsorbents: Classification, Characteristics, Chemical Nature, and Interaction with Contaminants
• Chapter 3 Impact of Factors on Remediation of Major Toxic Elements (Vanadium, Chromium, Nickel, Arsenic, Strontium, Cadmium, Mercury, Lead, Uranium) Via Batch Adsorption Process
• Chapter 4 Remediation of Essential Elements Exerting Toxicity on Excessive Exposure (Mn, Co, Cu, Zn, Se) Via Batch Adsorption in Response to Variable Factors and Elucidation of the Mechanism for the Batch Adsorption Process
• Chapter 5 Impact of Factors on Remediation of Miscellaneous (Fe, Cs) and Nontoxic Elements (Sc, Ti, Ga, Ge) Via Batch Adsorption Process
• Chapter 6 Impact of Factors on Remediation of Anions (Fluoride, Nitrate, Perchlorate, and Sulfate) Via Batch Adsorption Processes
• Chapter 7 Impact of Initial Concentration, Adsorbent Dose, and Ionic Strength on Batch Adsorption of Metals and Anions and Elucidation of the Mechanism
• Chapter 8 Kinetic, Isotherm, and Thermodynamic Studies for Batch Adsorption of Metals and Anions, and Management of Adsorbents after the Adsorption Process
• References
• Index