Synthesis of Metal Organic Framework (MOF) based Ca-Alginate for adsorption of malachite green dye

Wastewater contaminated by dye produced by the rapid industrialization is a global problem. One type of the dyes used in the industry is malachite green (MG). In this study, we reported the results of designing and synthesizing the Ca-Alginate (Metal Organic Framework (MOF)) as well as its application as an adsorbent to reduce the amount of MG in wastewater. The alginate used for the synthesis of Ca-Alginate was first obtained by extracting it from brown algae using sodium carbonate as a solvent. In this study, Ca-Alginate was obtained by ion exchange process using calcium chloride solution and calcination at a temperature of 900 °C. Based on the characterization data, it was found that the adsorbent has a macropore structure with a specific surface area of 0.614 m2/g and a total pore volume of 1.744 × 10−3 cc/g. The result of the FTIR characterization showed the presence of hydroxyl groups, symmetrical and asymmetrical carboxyl groups, and mannuronic and guluronic groups. These groups indicated the presence of alginate. The adsorption ability test on the MG dye was performed at various changes in contact time and concentration of the adsorbent, while the MG concentration on the adsorption process was examined using the batch system. The results showed that the highest reduction in MG occurred at the contact time of 120 min, 0.06 g/L of adsorbent dosage and 0.0055 g/L of initial MG concentration. Under these conditions the Ca-Alginate could adsorb up to 84.47% of MG. The adsorption kinetic of MG onto Ca-Alginate obeyed the modified pseudo-first-order (MPFO) model.Graphical abstract