Page 456 - Polymer-based Nanocomposites for Energy and Environmental Applications

Nanocomposite membrane for environmental remediation 413

For efficient removal of Pb ions from aqueous solution, two ultrafiltration techniques
were studied with the aim of developing a nanoparticle-improved separation process.
Further, the influence of various parameters such as the feed Pb ion and γ-PGA
concentrations and their proportions, the γ-PGA cross-linking ratio, and the pH of
the solution on the Pb removal efficiency and permeate flux was investigated. The
study revealed that γ-PGA could bind and remove >99.8% of the Pb ions from water
through a convenient, low-pressure ultrafiltration technique, resulting in a permeate
that satisfied the standard for drinking water recommended by the WHO.
Mark et al. [72] demonstrate that γ-PGA, a novel extracellular polyamide prepared
by Bacillus licheniformis, is a potential biosorbent for application in the removal
and recovery of heavy metals from industrial wastewater releases. γ-PGA has been
recognized for >70 years, and numerous researches have been performed on this
biopolymer [76].

15.5 Nanofiltration membrane bioreactor

Nanoscience and nanotechnology engineering technologies suggested that nano-
catalysts, nanoabsorbent, nanotubes, nanostructured catalytic membranes, nano-
powder, and micromolecules could overcome the existing issues regarding water
quality [77]. All the abovementioned nanoparticles and colloids have had a great
effect on water quality in treatment operation [78]. It has been reported in the literature
that integration of biological wastewater treatment with advance nanotechnology
makes a fast, effective, and durable water purification system [79].
During last few decades, membrane bioreactor (MBR) technology has appeared
as the most important and an effective wastewater treatment technology over the acti-
vated sludge process (ASP). In fact, MBR is considered one of the effective techno-
logies in wastewater purification system [80], as it has the ability to overcome the
drawbacks of the conventional ASP. These disadvantages of ASP include prerequisite
large space for secondary clarifiers, large sludge production, liquid-solid separation
concerns, and removal of recalcitrant restrictions [81]. The important characteristic
of MBRs is that they have been used for both municipal and industrial wastewater
treatment and recovery [82,83].
MBR is not a new technology in water and wastewater treatment but has the capa-
bility in treating wastewater that cannot be resolved using another treatment. Actually,
this system is a hybrid of biological treatment and filtration, but in some cases, the
inclusion of chemicals takes place to improve its efficiency. In the industrial sector,
the efficiency of MBR has been extensively studied, at the early 1990s when the first
large installation of MBR was studied in the United States by General Motors at its
plant in Mansfield, Ohio [84].
In North America, the first large-scale internal MBR arrangement that was installed
to purify wastewater from the food industry was installed in 1998 [85]. Due to high
capital and maintenance costs of the system and membrane maintenance, the research
on MBR has been dropped down. In 1990, submerged MBR was commercialized, and