Environmental Engineering Reference
In-Depth Information
Wijmans et al. [8] dealt with the solution-diffusion model in their review. The solution-diffusion model has emerged over
the past 20 years as the most widely accepted explanation for transport in dialysis, RO, gas permeation, and pervaporation. In
this review paper they dealt with the phenomenological equations for transport in these processes using the solution-diffusion
model and derived the equations starting from the fundamental statement that flux is proportional to a gradient in chemical
potential. The direct and indirect evidence for the model's validity is presented, together with a brief discussion of the transition
between a solution-diffusion membrane and a pore-flow membrane seen in nanofiltration membranes and some gas-permeation
membranes. The principal property of membranes used in separation applications is the ability to control the permeation of
different species. Two models are used to describe this permeation process. The first is the solution-diffusion model, in which
permeants dissolve in the membrane material and then diffuse through the membrane down a concentration gradient. A separa-
tion is achieved between different permeants because of differences in the amount of material that dissolves in the membrane
and the rate at which the material diffuses through the membrane. The second is the pore flow model in which permeants are
separated by pressure-driven convective flow through tiny pores.
nghiem et al. [9] delineated the removal of natural hormones by nanofiltration membranes with measuring, modeling, and
mechanisms. The removal of four natural steroid hormones—estradiol, estrone, testosterone, and progesterone—by nanofiltra-
tion membranes was investigated. Two nanofiltration membranes with quite different salt retention characteristics were utilized.
Renou et al. [10] reviewed the opportunities in landfill leachate treatment. In most countries, sanitary landfilling is nowadays
the most common way to eliminate municipal solid wastes (mSW). In spite of many advantages, the generation of heavily
polluted leachates, with significant variations in both volumetric flow and chemical composition, constitutes a major drawback.
Year after year, the recognition of landfill leachate effect on the environment has forced authorities to fix more and more strin-
gent requirements for pollution control. This paper is a review of landfill leachate treatments. The advantages and drawbacks
of the various treatments are discussed under the following topics: (i) leachate transfer, (ii) biodegradation, (iii) chemical and
physical methods, and (iv) membrane processes.
Childress et al. [11] related nanofiltration membrane performance to membrane charge (electrokinetic) characteristics. The
performance (i.e., water flux and solute rejection) of a thin-film composite (TfC) aromatic polyamide nanofiltration membrane
and its relation to membrane surface charge (electrokinetic) characteristics was studied.
Properties of nanofiltration membranes, model development, and industrial applications have been delineated in a disserta-
tion by Johannes martinus Koen Timmer [12]. The dissertation deals with industrial membrane processes and aspects of
nanofiltration. It also deals with the transport of lactic acid through RO and nanofiltration membranes. A model for mass trans-
port is described. In the pursuit of excellence, they delineated and described the entire pressure-driven membrane process. Their
research encompassed the dairy industry and the applications of nanofiltration.
Water engineering or environmental engineering is a boost to this research pursuit when we consider the work done by xia et al.
[13] for arsenic removal by nanofiltration and its application in China. According to their study, arsenic contamination of groundwater
and the associated health risks have been reported in many parts of China. nanofiltration is a promising technology for arsenic removal
since it requires less energy than traditional RO membranes. In this study, the removal of arsenic from synthetic waters by nanofiltra-
tion membranes was investigated. Arsenic rejection experiments included variation of arsenic feed concentration, pH, and existence
of other ionic compounds. The possible influence of nOm on As(V) rejection by nanofiltration membranes was also explored.
Orecki and Tomaszewska [14] did a fundamental research on oily wastewater treatment using nanofiltration process. The
authors lucidly and intensely dealt with a positive objective on the domain of oily wastewater treatment using the formidable
intellectual challenge of the application area of nanofiltration. The nanofiltration studies were carried out with a permeate
obtained from ultrafiltration (Uf) (used for the treatment of the oily wastewater from metal industry). The influence of trans-
membrane pressure on a permeate flux, the degree of rejection of oil and inorganic compounds were investigated with great
precision. The studies on the nanofiltration treatment of oil wastewater demonstrated a high effectiveness of the rejection of oil
and inorganic compounds. The permeate obtained from the treatment was free of oil. The nanofiltration process was carried out
in a pilot plant equipped with a tubular module with the AfC 30 membrane (PCI)—(the working area equal to 0.9 m
2
) and a
spiral wound module (with the nanofiltration 270-2540 membrane (film Tec—the working area equal to 2.6 m
2
). The studies
earlier predicted and performed showed that the membranes differed in molecular weight cut-off (mWCO). The mWCO of the
membranes were found out to be equal to 250 g/mol for nanofiltration 270-2540 and nanofiltration AfC30, respectively. The
results and discussion showed a remarkable pattern. The raw oily wastewater used in these studies was collected from metal
treatment industry. Apart from oil, the wastewater contained a lot of other contaminants, including solid state, lubricants, metal
fines and sometimes dissolved metals. Although the Uf membranes rejected oil in 90%, the permeate still contained different
solutes. The authors performed an integrated ultrafiltration and nanofiltration technique. The conclusions in this study were
affirmative. As a result of nanofiltration used as a second stage of oily waste water treatment the removal of organic compounds
(TOC) for the studied membranes (nanofiltration 270-2540 and nanofiltration AfC 30) exceeded 65%. moreover the cations are
