Adsorptive Removal of Phosphorus from Water Using Raw Lala Clam Shells as Adsorbent: Kinetic, Isotherm and Contour Prediction Studies

Abstract

Abstract

Phosphorus is a major contributor to water pollution, causing harmful algal blooms, oxygen depletion, hence eutrophication. Studies have shown that seashells can effectively remove phosphorus from water due to their calcium carbonate content. While seafood is widely consumed, the shells are typically discarded as waste. Previous studies have explored the use of seashells for phosphorus removal, but none have focused on using raw Lala clam shells. Hence, this study addresses this gap by exploring the potential of Lala clam shells as an adsorbent for phosphorus removal from water at different dosages (2g, 4g, 6g, 8g and 10 g). The adsorbents were characterized using XRD, SEM, EDXRF and FTIR analyses. Batch adsorption experiments assessed the effects of adsorbent mass and contact time on phosphorus removal efficiency. Kinetic analysis revealed that the pseudo-second order model best described the adsorption kinetics (R2 = 0.9964), indicating that the adsorption followed a chemisorption mechanism. Isotherm analysis showed that, although all models had low correlation coefficients, the Langmuir model provided a relatively better fit (R2 = 0.0122), suggesting that phosphorus adsorption occurred on a homogeneous surface, forming a monolayer of phosphorus molecules. The raw Lala clam shells could remove up to 64.2 % of phosphorus with the highest adsorption capacity of 0.0818 mg/g observed at 8 g adsorbent mass. Overall, these findings confirm that raw Lala clam shells exhibit moderate phosphorus removal performance and demonstrate potential as a low-cost and eco-friendly adsorbent, due to their abundance and minimal processing requirements, although further modification is required to improve their adsorption performance.