Carbon Dioxide – The Safer & More Efficient Alternative to Mineral Acids for Controlling Water pH

Author: Keshav Goela      Posted on: 06-12-21

Water is a fundamental necessity for all life. With changing climatic conditions, increasing population, rapid industrialization and urbanization, and depleting freshwater resources, we face the grave danger of extinction due to rising water scarcity.

To overcome the pressing threat of water scarcity, humans are turning to the seas. Today, desalination plays a crucial role in helping countries meet their increasing water demands. According to the US Geological Survey, desalination plants operate in several countries worldwide, with most of them located in Middle Eastern nations like Saudi Arabia, Kuwait, UAE, Bahrain and Qatar. More and more countries are turning to the seas and oceans to meet their industrial and drinking water needs.

Desalination: An Overview

Desalination converts salt water into potable water using RO (Reverse Osmosis) Technology. Today, carbon dioxide (CO2) has emerged as the most preferred treatment agent for desalination. Highly effective and safe, CO2 is considered the gold standard and sustainable form of desalination.

Let’s take a closer look at the impacts of desalination and how we can move to sustainable desalination solutions with CO2 and eliminate using harmful mineral acids completely.

The Drawbacks of Using Mineral Acids to Control Water pH

For decades, sulphuric acid and sodium hydroxide (caustic) were the go-to chemicals to control alkalinity in water treatment facilities. While these acidic compounds are effective, they have several potential drawbacks.

i. Acids are challenging to store, prepare and control.

ii. They are dangerous if not stored or handled correctly.

iii. Corrosive acids require special material for piping and storage.

iv. Plant owners must install safety showers and provide proper PPE equipment to operating personnel.

v. Using acids for controlling alkalinity requires frequent system repairs and replacement.

This is where carbon dioxide (CO2) comes into the picture. It's easy to handle, efficient, and eco-friendly. Continue reading to discover the benefits of CO2 for pH control.

The Working – How does CO2 control the alkalinity of water?

Carbon dioxide can help in changing the pH of the water safely. Here is a simple explanation of the process:

i. CO2 dissolves slightly in water to form carbonic acid (H2CO3), a weak acid.

ii. CO2 + H2O ----> H2CO3

The carbonic acid reacts slightly and reversibly in water to form H3O+, a hydronium cation and HCO3-, a bicarbonate ion.

iii. H2CO3 + H2O --> HCO3- + H3O+

These chemical reactions explain why water with a neutral pH of 7 acquires an acidic pH of approximately 5.5 when exposed to air.

Here are the significant benefits of using CO2 instead of mineral acids for controlling pH.

1. Safe to Use

Sulphuric acid and other chemicals are corrosive and require special storage and handling. In the event of a leak, sulphuric acid causes damages and injuries to operating personnel and equipment.

Unlike mineral acids, carbon dioxide is natural and safe to use, and it is inert and non-corrosive and doesn’t require special equipment for transfer or handling. When introduced into water, it forms a mild but reactive carbonic acid and doesn’t corrode metal. So, you don’t have to spend a fortune on special materials for downstream equipment and piping.

2. Efficient & Reliable

Both mineral acids like sulphuric acid and carbon dioxide have a similar neutralisation efficiency. The difference is in the way the reaction occurs:

i. CO2 changes the pH of water gradually and continuously.

ii. On the other hand, sulphuric acid changes the pH of water only after the alkalinity has been consumed.

3. Accuracy

Using CO2 minimises your risk of over-acidification. One of the biggest drawbacks of using sulphuric acid for controlling pH is that it can lead to over-acidification, which drops below the compliance range. With CO2, pH doesn’t drop below 6.0, helping you stay with the compliance range.

4. Low Maintenance

When compared with mineral acids, carbon dioxide is easier to maintain. It offers a trouble-free operation, thereby reducing downtime and frequent repairs.

5. Cost-Savings

As CO2 is safe and easy to use, you don’t have to invest in specialised equipment for storing and handling mineral acids. This reduces the overall cost of operation.

6. Eco-friendly

CO2 is an eco-friendly material and forms neutral carbonates and bicarbonates. On the other hand, using sulphuric acid results in secondary pollution due to chlorides and sulfates.

Applications of Carbon Dioxide for Water Treatment

Carbon dioxide can be used in the following applications:

i. Desalinated / Drinking water re-carbonation

ii. Process water pH control

iii. Wastewater treatment

iv. Industrial Water treatment

It's also used in the following industries: water and wastewater treatment plants, mining operations, car washes, chemical plants, service stations, industrial sites, and other processing plants.

GAS LAB Offers Safe and Efficient Solutions for Controlling Water pH

At GAS LAB, we have years of experience and expertise in supplying carbon dioxide to industries across sectors. Replacing mineral acids with CO2 offers various benefits. You no longer have to invest in the infrastructure to store acids safely. Besides increasing the safety levels of your plants, using CO2 also reduces overall operational costs.

As a result, you can improve your plant capacity and output without causing any damage to the environment. If you are looking for a cost-friendly and safe option to control the pH of wastewater, get in touch with our team to explore our solutions.