This study utilised an experimental research design to evaluate the effectiveness of biodegradable adsorbents sourced from agro-waste materials for the purpose of saltwater softening. Local farmers provided agro-waste materials like rice husk, coconut shell, banana peel, and sugarcane bagasse. These were then used to make cheap adsorbents. First, the collected items were carefully rinsed with distilled water to get rid of dust and other impurities. Then, they were dried in the sun for about 48 hours. After they dried, the materials were ground into fine particles using a grinder. To make the materials better at adsorbing, some of them were heated to high temperatures (400–500°C) to make activated carbon. Others were treated with dilute hydrochloric acid and then washed with distilled water until the pH was neutral. For testing, the adsorbents that were made were kept in airtight containers. The seawater samples were collected in sterile plastic containers from a coastal source and then filtered to remove any particles that were not in the water before being tested. Standard laboratory methods, such as the EDTA titration method for hardness testing, were used to find the starting values of total hardness, calcium ions, magnesium ions, pH, and conductivity. We put 100 ml of saltwater in a beaker and added 2 grams of the adsorbent we made to it for the softening test. To allow the adsorbent and water to interact enough, a magnetic stirrer was used to stir the mixture for about 30 minutes. After stirring, the solution was filtered, and the water that had been processed was tested again for hardness, calcium, magnesium, pH, and conductivity. The same procedure was used for each type of adsorbent to see how well they worked. We put the data we got from the experiment into tables and used the percentage removal method to look at it. The results showed that all of the agro-waste adsorbents made things less hard to some extent, with activated coconut shell and rice husk carbon being the most effective. The decrease in calcium, magnesium, and conductivity confirmed effective softening, and the pH levels moving closer to neutral showed that the water quality had improved. This study shows that biodegradable agro-waste adsorbents are a good, eco-friendly, and cheap way to soften saltwater.