The Absorption of Congo Red (CR) Synthetic Dye Using the Metal-Organic Framework Calcium Alginate (MOFCA) Adsorbent

Chemical Engineering Department, Faculty of Industrial Engineering, UPN Veteran Yogyakarta, Indonesia

^* Corresponding author: mahreni@upnyk.ac.id

Abstract

Congo Red (CR) is an anionic dye with a benzylic chemical structure that is naturally difficult to decompose. This research aims to produce metal-organic framework calcium alginate (MOFCA) as an natural adsorbent that is efficient as adsorbent for CR dyes. MOFCA production are through extraction of brown algae, then precipitation of Natrium Alginate (NA) using calcium hydroxide (Ca(OH)₂), and calcination at a temperature of 900ºC during 2-hourto to produce MOFCA adsorbent. MOFCA characterization using FTIR, SEM-EDX, and BET. The application of MOFCA as a CR adsorbent is carried out to determine the adsorption kinetics model. The results show that the highest reduction in CR concentration is at a MOFCA adsorbent concentration of 0.03 g/L, contact time of 180 minutes, pH=5 with a constant stirring speed of 120 rpm, and CR concentration of 0.04 g/L. The CR adsorption kinetics on MOFCA follows the MPFO-2 model; the adsorption isotherm model follows the Langmuir model; the MOFCA surface adsorption capacity is 1202.7075 mg/g. The adsorption rate obtained was 97.0840%. MOFCA has previously been studied by the same researchers as a Malacite Green (MG) adsorbent. The results showed that the highest MG reduction occurred at a contact time of 120 minutes, an adsorbent dose of 0.06 g/L, and an initial MG concentration of 0.0055 g/L. Under these conditions, Ca-Alginate was able to adsorb up to 84.47% of MG. In conclusion, MOFCA is an environmentally safe, efficient, and economical adsorbent is feasible to develop commercially.