Page 256 - Materials Chemistry, Second Edition

Technologies for Treatment of Heavy Metal–Contaminated Groundwater 237

onward, the retentate can be dealt with, keeping in mind the end goal to recover
metallic particles and also to reuse the polymeric agent.

11.5.4.2 Nanofiltration
Nanofiltration (NF) has remarkable properties. The detachment system includes
both steric (pore measure) and electrical mechanisms (oppositely charged surface
groups). The layers used for NF can be portrayed as “low-weight turn around osmo-
sis layers.” NF is an intermediate procedure between UF and RO. NF is a promising
innovation for the removal of excess metal particles, for example, nickel, chromium,
copper, and arsenic, from wastewater (Muthukrishnan and Guha, 2008; Murthy and
Chaudhari, 2008; Ahmad and Ooi, 2010). NF treatment benefits from simplicity of
operation, dependability, and low energy use as well as high effectiveness of con-
tamination removal.
11.5.4.3 Reverse Osmosis
RO treatment uses a semi-permeable membrane, permitting the liquid that is being
cleaned to go through it while rejecting the contaminants. RO is a prevalent waste-
water treatment alternative in synthetic and ecological design. RO is a weight-driven
film treatment whereby water can unreservedly go through the membrane while cat-
ionic compounds are retained (Greenlee et al., 2009). RO film pore sizes can be
as little as 0.1 nm. RO can be used for systems with low levels of dispersed metal
(micromolar to millimolar range).

11.5.5 coagulaTion
Coagulation stands out among the most essential techniques for wastewater treat-
ment, yet the primary objects of coagulation are just hydrophobic colloids and sus-
pended particles. With the specific end goal to remove both dissolved heavy metals
and insoluble substances effectively by coagulation, a sodium xanthogenate group
was joined to polyethyleneimine. This new kind of coagulant was an amphoteric
polyelectrolyte (Chang and Wang, 2007).

11.5.6 elecTrocHeMical TreaTMenT
Electrochemical treatment is an electrically supplemented system such as ultra-fil-
tration. It is widely used to remove toxic heavy metal particles from wastewater
(Wang et al., 2007). It generally requires a vast capital venture to start the process,
supplemented by long-term operational and support costs, and the cost of the electri-
cal supply limits its applicability. The electricity can be used in various procedures,
for example, electro-coagulation, electro-floatation, and electro-dialysis.

11.5.6.1 Electro-Coagulation
Electro-coagulation is an electrochemical approach with a reactive anode and cath-
ode (iron or aluminum electrode), which uses an electrical current to remove metals
from a solution. The electro-coagulation method is additionally powerful in remov-
ing suspended solids, dispersed metals, tannins, and colors. The contaminants found