Nanosized Metal Oxide-Based Adsorbents for Heavy Metal Removal: A Review - Advanced Materials for Agriculture, Food and Environmental Safety - page 242

9.1 Introduction

In recent years, heavy metal pollution has become one of the most seri-
ous environmental problems. h e presence of heavy metals even in trace
amounts can be toxic and hazardous to both l ora and fauna. With the rapid
growth of industries such as mining, surface i nishing, energy producing,
metallurgy, steel and iron, electroplating, electrolysis, leather and photog-
raphy, the wastes containing heavy metals are causing a serious threat to
the environment. Some elements like Fe, Zn, Cu, Co, Cr, Mn and Ni are
required in small quantities for human metabolism, but may be toxic at
higher levels. Others like lead, mercury, cadmium, arsenic, etc., have no
benei cial role and are positively toxic [1, 2]. h e environmental pollution
from heavy metals can arise from anthropogenic and natural sources. With
the rapid increase in industrialization, anthropogenic sources of pollution
have been increased (Table 9.1). Toxic chemicals enter the human body

Table 9.1 Anthropogenic source of heavy metals [8,9].

Metal Source

Mercury (Hg) Chlor-alkali plants, thermal power plants, l uorescent

lamps, hospital waste, electrical appliances, etc.

Arsenic (As) Geogenic/natural processes, smelting operations,

thermal power plants, fuel burning

Lead (Pb) lead acid batteries, paints, E-waste, Smelting

operations, coal-based thermal power plants,
ceramics, bangle industry

Copper (Cu) Mining, electroplating, smelting operations

Cadmium (Cd) Zinc smelting, waste batteries, e-waste, paint sludge,

incinerations and fuel combustion

Nickel (Ni) Smelting operations, thermal power plants, battery

industry

Molybdenum (Mo) Spent catalyst

Zinc (Zn) Smelting, electroplating

Vanadium (V) Spent catalyst, sulphuric acid plant

Chromium(Cr) Mining, industrial coolants, chromium salts

manufacturing, leather tanning