**Abstract**

Heavy metals are one of the toxic pollutants threatening the human kind by causing various health issues. The detection of such polutants are of important environmental concern and we need a real-time monitoring equipment. Many researchers have established a number of approaches for the detection of these heavy metals so far. But, the development of one time use sensors for the quick, and real time detection of toxic heavy metals is in great demand. The electrochemical methods like cyclic voltammetry, is proved to be one of the best and popular methods, and are preferred over other electrochemical methods because of its high sensitivity, selectivity, anti-fouling, quick and accurate detection. In the present book chapter, we will discuss the various modifiers used to detect the arsenic, cadmium, and lead heavy metals using cyclic voltammetry.

**Keywords:** heavy metals, electrochemical sensors, cyclic voltammetry, electrodes, toxic pollutants

### **1. Introduction**

Heavy metals occur either naturally by geological activities, or by agricultural and industrial wastes. Any elements exhibiting relatively high molecular weight and more than 5 g/cm3 density are considered as heavy metals [1]. They are generally non-biodegradable and toxic in nature due to their ability to transform from one oxidation state to another easily. The heavy metals can cause bioaccumulation because of absorption of them by plants and animals living in that contamination areas [2] and causes various health effects like malfunction of gastrointestinal, nervous system, kidney and immune system, followed by birth defects, skin lesions, and cancer [3]. **Figure 1** depicts the different organs of humans affected by the consumption of various heavy metals.

The agricultural and industrial wastes like pesticides, fungicides, refineries, fertilizers, mining, smoking, nuclear fission plants, chemical industry, paint, electroplating, welding, automobiles, batteries, are the major sources of heavy metal ions [5]. Currently, there are more than 50 heavy metals are known and some of them are metalloids, actinides, transition elements and lanthanides [6]. The elements like lead, mercury, arsenic and cadmium are considered as very toxic and their consumption

#### **Figure 1.**

*Various heavy metals affecting the different organs of human [4].*

in small amount can cause serious health issues. But, some of the heavy metals are human friendly and their consumption in trace amount can maintain good health. Therefore, regular determination of the heavy metals is advisable in the contamination areas. **Figure 2** depicts the possible ways of heavy metal exposure, their impact on human health and their mechanism.

Many researchers used cold vapor atomic fluorescence, atomic absorption, and emission spectroscopies and inductively coupled plasma techniques [8] to detect heavy metals. But these methods are time consuming, chances of contamination, requires huge manpower and area. Therefore, we need some standard analytical methods to detect the presence of heavy metal ions in foods, plants, animals, water, and soils. Electrochemical methods like cyclic voltammetry [9–16], stripping voltammetry,

*A Review on Cyclic Voltammetric Investigation of Toxic Heavy Metals DOI: http://dx.doi.org/10.5772/intechopen.108411*

**Figure 2.**

*The possible ways of heavy metal exposure, their impact on human health and their mechanism [7].*

differential pulse voltammetry, and polarography are so far best and popular choice to determine the various heavy metals in the environment. These methods are cheap, highly accurate, quick, robust in nature. Among them, cyclic voltammetry is proved to be one of the better and highly advantageous electrochemical methods used to detect organic, inorganic, organometallic, and biological heavy metal ions. High sensitivity, fast response, live monitoring data acquisition, wide detection limit, and possibility of simultaneous detection of multi elements by surface functionalization has made it one of the popular choices among the environmentalists used to detect the heavy metals [6, 17–21]. The present book chapter focus on the recent developments, current challenges, and prospects for future research in cyclic voltammetric determination of lead, arsenic, and cadmium in the environment. We hope that this book chapter will be useful for all the environmental researchers working on heavy metals.

#### **2. Electrochemical determination of Lead (Pb) using cyclic voltammetry**

Lead is a bluish-gray metal generally found in the earth crust. Lead is very poisonous metal directly affect the human nervous system and causes severe headaches, and memory loss [22]. Lead is very dangerous woman especially during the pregnancy, when a pregnant woman consumes lead, then it reaches the fetus and causes premature childbirth, abnormal growth, and low weight of the fetus. Lead also affect the brain developments in children and causes the abnormalities [23]. Therefore, people working in lead contamination zone must regularly check the amount of lead in their body.

Mei et al. have reported the use of TC4 arene-modified screen-printed carbon electrode (SPCE) to detect lead ions in river water using cyclic voltammetry [22].

**Figure 3.**

*(a) The schematic representation of electrode preparation to determine Pb2+, and (b) binding of electrode with Pb2+ [22].*

**Figure 3** demonstrates the schematic representation of electrode preparation to determine Pb2+. They reported the 0.7982 × 10−2 ppm detection limit for Pb2+ followed by the excellent reproducibility and stability. **Figure 4** depicts the current response of the sensor detecting Pb2+ ions at different pH levels.

Riyanto has determined lead ions by cyclic voltammetry method using platinum wire as a working electrode in wastewater [24]. Authors reported that, they successfully detected the lead from wastewater with correlation of determination (R2 = 0.999), LOD of 0.9029 mg/L, limit of quantification (LOQ ) of 3.0098 mg/L and recovery of 100.67% respectively. They found that, the electro-oxidation of lead on Pt wire electrode occurs in a reversible system and reported that the analytical parameter from cathodic peak is better compared to anodic peak for analyzing of Pb using CV method. They claimed that, the fabricated electrode is simple, economic and showed an excellent selectivity, accuracy, sensitivity, reproducibility [24].

#### **Figure 4.**

*Current response of electrode during electrochemical determination of lead ions in a KCl supporting electrolyte at different pH [22].*

#### *A Review on Cyclic Voltammetric Investigation of Toxic Heavy Metals DOI: http://dx.doi.org/10.5772/intechopen.108411*

Khodari et al. İnvestigated the cyclic voltammetric behavior of lead ions well water samples using glassy carbon electrode [25]. Cyclic voltammogram showed an anodic peak at −520 mV for lead ions. Authors reported that, the glassy carbon electrode showcased an excellent linear response to a good linear response to Pb2+ in the concentration range from 8 × 10−6 M to 1 × 10−4 M with a detection limits of 2 × 10−7 M. They also studied the effect of scan rate, deposition time, deposition potential, and the pH of the supporting electrolyte on lead ions. They claimed that, the fabricated electrode is accurate, precise, highly selective in determining the lead ions in well water.

Honeychurch used carbon rod electrode extracted from zinc-carbon batteries to determine the traces of lead ions present in tap water sample using cyclic voltammetry [26]. Author studied the electrochemical behavior of Pb at different supporting electrolytes like ortho-phosphoric acid, HNO3, HCl, CH3COOH, KCl and malonic acid. They found the optimum electrochemical condition of a supporting electrolyte

#### **Figure 5.**

*Effect of acetic acid supporting electrolyte concentration on the cyclic voltammetric behavior of 116 μM Pb: (a) 0.0 M, (b) 0.03 M, (c) 0.1 M, (d): 0.66 M, and (e) 3.0 M [26].*

of 4% v/v acetic acid, with a deposition potential and time of −1.5 V (vs. SCE) and 1100 seconds as per the **Figure 5**. They reported the linear range of 2.8 μg/L to 110 μg/L and a detection limit of 2.8 μg/L with 95.6% mean recovery.
