Development of an Adsorbent Material for Removing Natural Organic Materials from Water

Humic acid (HA) is the most prevailing component of Humic substances in total organic carbon (TOC) which is the main fraction of natural organic matter (NOM) in water sources. Studies in many regions of Sri Lanka showed that the TOC levels are higher than the desirable level of 2 mg/l. Even though the presence of NOM higher than the tolerable level may affect the quality of water, there is no treatment procedure carried out other than the conventional treatment process. Due to the low efficiency of conventional treatment processes in removing NOM, adsorption is proposed as a cost-effective, efficient, and simple technique that overcomes the drawbacks of other techniques. Chitosan is an excellent natural, biodegradable, and abundant adsorbent material. In this research, raw chitosan beads and chitosan/hydroxyapatite (Hap) composite beads made with chitosan powder, eggshells, and poly-ethylene–glycol (PEG), were used to investigate and compare the removal efficiencies of the adsorbent and performance in removing HA. A zero-point charge (pHzpc) study was conducted to characterize the adsorbent materials. Further, the behaviour of the materials with humic acid at neutral pH was investigated using the effect of the contact time, the adsorbent dosage on the removal efficiencies of raw and modified chitosan adsorbents. Moreover, Kinetic studies and isotherm studies were conducted for adsorbents by using a synthetic wastewater sample at neutral pH. A removal efficiency of 74, 60%, and removal capacity of 1.37 mg/g, 1.11 mg/g was achieved for raw and modified chitosan materials, respectively.