An Adsorbent Based on Humic Acid-Like and Carboxymethyl Cellulose for Efficient Pollutant Removal from Synthetic Wastewater

Adsorbents from green and sustainable source are highly desirable for practical applications. In this study, humic acid-like substance extracted from dry horse dung powder and carboxymethyl cellulose (CMC) were adopted to fabricate a composite immobilized on magnetic precipitates of magnetite. The as-prepared adsorbent, denoted as CMC-MHDHA, was analyzed by infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission and scanning electron microscopy equipped with energy dispersive X-ray (TEM and SEM-EDX), thermo gravimetric analysis (TGA), and vibration sample magnometer (VSM). Application to the synthetic wastewater of Pb (II) and Rhodamine B (RhB), a high Langmuir monolayer adsorption capacity of 63.38 and 42.78 mg/g was achieved over CMC-MHDHA, respectively. The fabricated adsorbent was also demonstrating quick and easy retraction of pollutant-loaded adsorbent by an external magnet with the magnetic strength of 40.7 emu/g. Based on the estimated free adsorption energy of Dubinin-Radusckevich (D-R) isotherm model, the adsorption interaction of both Pb (II) (9.76 kJ/mol) and RhB (12.39 kJ/mol) with CMC-MHDHA was mainly occurred by ion exchange mechanism. Adsorption rate analysis at the initial adsorbate concentration ranged from 50 to 400 mg/L of both Pb (II) and RhB showed that the rapid adsorption generally occurs in early 20 minutes then slow down and reaches equilibrium after 180 minutes. The Ho (pseudo second order) kinetics model represent appropriately the adsorption of both Pb (II) and RhB onto the adsorbent. The developed adsorbent is also reusable with 72.3% of stability in pH 11. Therefore, the adsorbent of CMC-MHDHA is suggested to be a promising candidate for adsorption applications.