Adsorption of sulfate ions from water by CaCl2-modified biochar derived from kelp

Abstract

In order to prevent the slow degradation of pristine water ecosystems caused by increasing SO₄²⁻ in natural water bodies (lakes and rivers), innovative and cost-effective remediation techniques are urgently required. Using natural waste kelp trimmings as the carbon source, the CaCl₂ activation-carbonation process generates an ecologically acceptable biomass carbon adsorbent. To adsorb SO₄²⁻ from an aqueous solution, kelp-based activated carbon adsorption material (KPC) was created. According to FT-IR research, KPC has many active groups, namely OH and C–O, which further improve adsorption efficiency. The adsorbent had the following property characteristics: The TEM-EDS, XPS, and BET characterization studies were used to describe the adsorbent, and the findings showed that Ca²⁺ was present on the surface of the unactivated kelp-based activated carbon material (UKC). Compared to UKC, KPC has a porous structure and a greater specific surface area. KPC shows good affinity for SO₄²⁻ with a maximum sulfate adsorption capacity of 866.98 mg g⁻¹, which is much higher than that of other materials (such as grapefruit peel (35.21 mg g⁻¹ adsorption) and coconut shell (4.90 mg g⁻¹ adsorption)). Kinetic studies showed that the adsorption of sulfate ions from simulated water (SW) and Ulungu lake water (LW) followed quasi-secondary kinetics. Isotherm data analysis shows that the Langmuir isotherm model is compatible with SO₄²⁻ in simulated water.