Design of a Process for the Removal of

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Design of a Process for the Removal of Chromium
from Ground Water
Group Members
Amal Al-Harbi
Areej Hussain
Naeema Karam
Sabah Mubarak
Faculty Advisor
Dr. Muftah H. El-Naas
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Design of a Process for the Removal of Chromium
from Ground Water
Group Members
Amal Al-Harbi
Areej Hussain
Naeema Karam
Sabah Mubarak
Faculty Advisor
Dr. Muftah H. El-Naas
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Outline
Introduction
Adsorption Experiments
Process description and material balance
Process design
Cost estimation
Environmental impact
Conclusions
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Introduction
The UAE is one of the worlds biggest consumers
of water
Sources of water supply in the UAE

• Ground water
• Desalinated water
• Recycled sewage water

Ground water accounts for about 30 of drinking
water
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Problem Definition
What is the problem in Al-Ain Ground Water?
The Northern Region Wells in Al-Ain are highly
contaminated with Chromium.
The high concentrations of Chromium led to the
closure of 40 wells in this region.

• Dry desert climate
• Pumping more water
• Dissolving of Cr from soil and rock of the
  adjoining area

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Chromium
Exists in hexavalent Cr(VI) and trivalent Cr
(III) forms Hexavalent form is more toxic than
trivalent
Source of Cr

• Human activities
• Industrial effluent

Effect of Cr on health

• Cancer in digestive tract and lungs
• Nausea and Vomiting

The maximum allowable concentration of Cr in
drinking water according to EPA and national
standards is 0.05 mg/L
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Objective
The main objective of this project is to design
an economical and practical process for the
removal of chromium from contaminated water
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Adsorbent (68.26 kg/hr Date pits)
Material Balance
Groundwater (9m3/hr, 9000 kg/hr) 0.11ppm of Cr)
Clean water (8.98 m3/hr, 8983 kg/hr with 0.029ppm
Cr)
Date pits wet cake (68.26 kg/hr date pits
contaminated with Cr) 17 kg/hr of water
Treatment process (Three main units with six
stages
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Process description
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Design of adsorption vessel
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Design parameters for one CST
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Design parameters for one CST
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Design of filters
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Design of pumps
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Design of pipes
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Experimental Work

• Materials
• Date Pits.
• Activated Date Pits
• Algae (Chlorella Vulgaris).
• Equipment
• pH meter.
• Shaker.
• Atomic Adsorption Spectrophotometer (AAS).
• Membrane syringe filters.
• Preparation of solutions.
• A stock solution of Cr (VI) (1000 ppm) was
  prepared in distillate water with K2Cr2O7.

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Results and discussion

• 1. Effect of contact time

Figure 1.1 Effect of contact time on Cr removal
using Date Pits and Algae (Initial Cr
concentration of 5 ppm Adsorbent concentration
of 6 g/lpH 2).
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Results and discussion
1. Effect of contact time
Figure 1.2 Effect of contact time on Cr removal
using Activated Date Pits (Initial Cr
concentration of 5 ppm Adsorbent concentration
of 1 g/lpH 2)
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2. Modeling of Adsorption kinetics

• The time influence was modeled by using two
  models for different adsorbents as follow
• Pseudo first order model
• Where
• qe The sorption capacities at equilibrium,
  (mg/g).
• qt The sorption capacities at time t, (mg/g).
• k1 The rate constant of pseudo first order
  sorption, (1/min).

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2. Modeling of Adsorption kinetics

• Pseudo second order model
• Where
• qe The sorption capacities at equilibrium,
  (mg/g).
• qt The sorption capacities at time t, (mg/g).
• k The rate constant of pseudo second order
  sorption, (g/mg.min).

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Table 2.1. The pseudo first and second order
parameters with R2.
Sorbent C0(ppm) Pseudo-First Order
Pseudo-Second Order
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3. Effect of pH
Figure 3.1 Effect of pH on Cr removal Algae
concentration of 6g/l.
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3. Effect of pH
Figure 3.2 Effect of pH on Cr removal Date
Pits concentration of 6g/l.
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3. Effect of pH
Figure 3.3 Effect of pH on Cr removal Date
Pits concentration of 6g/l.
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4. Adsorption isotherm

• The isotherm behaviors of different adsorbents
  were modeled using Langmuir equation as follow
• Also the isotherm were modeled using Freundlich
  equation presented as follow
• Where
• qmax The maximum uptake.
• b The theoretical monolayer sorption saturation
  capacity.
• kf and n Are Freundlich constants.

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Table 4.1. Langmuir and Freundlich constants with
R2 .
Sorbent Langmuir constants
Freundlich constants
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Groundwater experiments

• The real groundwater experiments were conducted
  using adsorbent concentration of 2g/L, and the
  samples were shaken for two hours to reach the
  maximum percentage removal as obtained in
  previous experiments.
• The experiments showed that
• The effect of pH on Chromium removal at very low
  concentrations (0.08 to 0.42 ppm) was not as
  important as for high concentrations (1,5 ppm).
• The removal at pH (7-8) and pH 3 reaches 71, 78
  using Activated Dates Pits for initial
  concentration of 0.32. Hence, no need for pH
  adjustment.

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Cost Estimation
Total production cost 160,170.53 Dhs
Production cost 2.17 Dhs /m3
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Equipment Cost
Ce CSn Where Ce purchased equipment S
characteristic size parameter size in units . n
index for type of equipment
Example Tanks of tanks 6 Cost (1998)
6240030.6 278,37.82 Cost (2003) 109,961.59
Dhs
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Environmental Impact Assessment
Example of wells concentrations with actions
1(very low)-----------5(severe)
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Conclusions

• The optimum pH for the removal of Cr(VI) ion by
  the three adsorbents is around 3. The maximum
  removal of Cr(VI) was found to be around 76 for
  Algae, 74 for Date Pits, and 99 for Activated
  Date Pits . The maximum removal reaches
  equilibrium stage after one hour for the three
  adsorbents.
• The pseudo-second order model provides the best
  correlation of the rate data.

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• The optimum concentrations were 0.2, 0.02 and
  0.02 (g/L) for Algae, Date Pits and Activated
  Dates Pits, respectively at different initial
  concentration of Cr solution. Also it was found
  that more advantageous results were obtained with
  Activated Date Pits compared to the results
  obtained with raw Date Pits.
• The date pits was selected for real ground water
  treatment

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Life is made of water Dont waste it