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

Methods of boron removal

Reverse osmosis

Ion exchange

Adsorption

Coagulation and precipitation

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

Factors affecting RO

pH

Pressure

Temperature

Salt concentration

Effect of recovery

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.

Experimental Setup

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