Ultrahigh removal of toxic basic green 4 from wastewater by zinc cobaltite filled calcium alginate composite microbeads: Isotherm, kinetic, and thermodynamic studies

Abstract

Since dyes in water have become a common problem recently, the aim of the present study was to create a highly effective material using sodium alginate (SA) biopolymer and zinc cobaltite (ZC). ZC was added to the SA biopolymer gel at 10 %, 20 %, and 30 % by weight to form calcium alginate/ZC (CA/ZC) composite microbeads. Basic green 4 (BG4) dye was effectively adsorbed from contaminated water using these composites as a surface. SEM, FTIR-ATR, XRD, pHpzc, and BET studies were used to characterize the adsorbents. The pHpzc value was determined to be 6.70. From BET analysis, the surface area, pore diameter, and pore volumes of the ZC adsorbent were determined as 77.35 m2/g, 13.27 nm, and 0.2566 cm3/g, respectively, while those of the SA/ZC/30 were determined as 95.61 m2/g, 11.28 nm, and 0.3371 cm3/g, respectively. The effects of temperature (298-318 K), initial pH (2-10), treatment time (0-150 min), adsorbent mass (0.01-0.15 g/50 mL), initial concentrations (100-800 mg/L), and ionic strength on the dye removal efficiency were studied. The total water content of the prepared beads was determined as 97 %. Various nonlinear isotherm models, such as Langmuir, Freundlich, Temkin, Jovanovic, and Hill, were used to fit the raw adsorption data. Using the Langmuir model, the adsorption capacity of CA/ZC/30 was found to be 750.9 mg/g at 298 K. Pseudo-first order, pseudo-second order, and Elovich kinetic models were used to investigate the kinetics of dye removal. These kinetic studies determined that the process occurred via a chemical adsorption mechanism. Thermodynamic studies determined that the process was endothermic and spontaneous. All studies indicated that the prepared composite microbeads have a high surface area, are natural and sustainable, and have high performance. They can be used as a highly effective potential adsorbent for the removal of cationic pollutants from aqueous solutions.