Calcium hydroxyapatite (Ca-HAp) was synthesized from calcium carbonate (CaCO₃) extracted from a paper mill sludge. The extraction of CaCO₃ was carried out by chemical precipitation process and synthesized to HAp nanoparticle under appropriate stoichiometric condition through wet chemical precipitation process. The size of the HAp nanoparticle was 42.5 nm under an optimized aging period of 24 h. This work aims in the batch adsorption of arsenic, an anionic metal arsenic in the form of Arsenite: As(III) on the synthesized Ca-HAp in laboratory scale. Batch kinetics studies were conducted for varying operational parameters such as temperature, initial adsorbate concentration, dye solution pH and rotation speed (RPM). In comparison with the two suggested isotherm models, Langmuir isotherm was suited to this adsorption process with a correlation coefficient of 0.92 and isotherm constant as 1.18 (K_L). Chemisorption was found to be the rate-limiting mechanism for the sorption of arsenite onto Ca-HAp and thus followed pseudo-second-order kinetics. A maximum monolayer adsorption of 0.43 mg/g of arsenic was obtained at an equilibrium time of 60 min with 93% to 94.2% removal efficiency.

羟基磷灰石钙 (Ca-HAp) 由从造纸厂污泥中提取的碳酸钙 (CaCO _{3 ) 合成。}CaCO _3的萃取通过化学沉淀法进行并通过湿法化学沉淀法在适当的化学计量条件下合成HAp纳米粒子。在 24 小时的优化老化期下，HAp 纳米颗粒的尺寸为 42.5 nm。这项工作旨在在实验室规模的合成 Ca-HAp 上批量吸附砷，一种以亚砷酸盐：As(III) 形式存在的阴离子金属砷。对不同的操作参数进行批量动力学研究，例如温度、初始吸附物浓度、染料溶液 pH 值和转速 (RPM)。与建议的两种等温线模型相比，Langmuir 等温线更适合这种吸附过程，相关系数为 0.92，等温线常数为 1.18 ( K _L）。发现化学吸附是亚砷酸盐吸附到 Ca-HAp 上的限速机制，因此遵循准二级动力学。在 60 分钟的平衡时间下，砷的最大单层吸附量为 0.43 mg/g，去除效率为 93% 至 94.2%。