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Presented by:-Akhilesh Kumar Kushwaha
M.Tech – Chemical EngineeringMalaviya National Institute of Technology Jaipur
Removal of Boron from Water
using Reverse Osmosis
National Conference on Water Quality Management
(NCWQM) – December20-22 , 2012
Contents Introduction
Health Risks and Ecological implications
Methods of removal of boron
Reverse osmosis
Factors affecting RO
Advantages and disadvantages of RO
Boron analysis
Experimental setup
Results and discussions
Conclusions
References
Introduction
Boron is a naturally occurring element found in rockand soil
Surface and ground waters as well as waste waters at aconcentration level of 5-100 mg/liter
In water, boron exists in the form of boric acid
Recent rapid growth in water desalination by ROtechnology, the issue of boron removal has come to thelight
Natural sources and Anthropogenic sources
Health and Ecological Implications
WHO permissible limit for drinking water (0.5mg/l)
Borism, teratogenic effects, nausea etc.
Boron is an essential nutrient for plants
Chlorosis (discoloring of leaves) & necrosis
Plants can occasionally be stressed by boron toxicity and salinity simultaneously
Reverse Osmosis (RO)
In reverse osmosis, two solutions are separated by a semi-permeable membrane, pressure is applied to reverse the natural flow of the water. This forces, the water to move from the more concentrated solution to the less concentrated
Spiral wound membrane element
RO…Solution diffusion model:
The RO membrane has a homogeneous, nonporous surface layer
Both the solute and solvent dissolve in this layer and then each diffuses across
Diffusion is due to its own chemical potential gradient across the membrane
Gradients are the result of concentration and pressure differences across the membrane
Transport across the membrane:
Jw = A(∆P-∆ᴫ )
RO...
Different stages in RO treatment process:
Pretreatment
Pressurization
Separation
Post treatment
Advantages & disadvantages
Advantages
Can treat low to high TDS seawater
Low maintenance
Green technology
Single step separation
Installation cost low
Disadvantages
Membrane change
High membrane cost
Parameters should not exceed their limits
Pretreatment required
Boron Analysis Method
Curcumine Spectrophotometer Method:
Boric acid on reaction with curcumine(diferuolylmethane – C21H20O6) in acidic solution results in a red color boron – chelate complex called Rosocyanine.
Absorbance of this solution was taken at 540 nm.
Result and DiscussionThe effect of pH on % boron rejection:
Conc. = 20 ppm & P = 5 bar at Temp = 23 C
Fig(1): Variation of boron rejection with pH
0
2
4
6
8
10
12
0 20 40 60 80 100 120
pH
% removal
Results Contd…Variation of % boron rejection with applied pressure:
Temp = 23 C , Conc. = 20 ppm & pH=10
Fig(2): effect of pressure on % boron removal
0
20
40
60
80
100
120
0 20 40 60 80 100 120 140
% B
ron
re
ject
ion
Time(min)
2 bar
5 bar
Results contd...Variation of permeate boron conc. with time
Conc. = 20 ppm & P = 5 bar at Temp = 23 C , pH= 10
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 20 40 60 80 100 120 140
pe
rme
ate
bro
n c
on
c.(p
pm
)
Time(min)
ConclusionThe outcome of this work implies that:
The % boron rejection was observed to increase withincrease in pH from normal to higher pH which is inaccordance to the theoretical predictions
On increasing the feed pressure, the % boron rejectionwas observed to increase accordingly.
References
C D Tagle , V J R Ternero, A M D Torres Boron removal efficiency in small seawater Reverse Osmosis systems, Desalination 265 (2011) 43–48
Alyson Sagle and Benny Freeman, Fundamentals of Membranes for Water Treatment.
B. Panete, L.G. Rodriguizw Current trends and future prospects in the design of seawater reverse osmosis desalination technology, desalination, volume208.
A. E. Ylmaz, R. Boncukcuoğlu, M.Kocake, E. Kocadağistan, An empirical model for kinetics of boron removal from boron containing wastewaters by the electro coagulation method in a batch reactor, Desalination 230 (2008) 288–297.
M. Htun O, L.Song Effect of pH. and ionic strength on boron removal by RO membranes, Desalination 246 (2009) 605–612.
Drinking Water Health Advisory For Boron, EPA