Applicability of a novel and highly effective adsorbent derived from industrial palm oil mill sludge for copper sequestration: Central composite design optimisation and adsorption performance evaluation

• Main Authors: Lee, Xin Jiat, Hiew, Billie Yan Zhang, Lai, Kar Chiew, Tee, Wan Ting, Thangalazhy-Gopakumar, Suchithra, Gan, Suyin, Lee, Lai Yee
• Format: Article
• Published: Elsevier 2021
• Subjects: TA Engineering (General). Civil engineering (General)
• Online Access: http://eprints.um.edu.my/28572/

Palm oil mill sludge (POMS) is a significant industrial waste generated in Malaysian palm oil mills. The re-utilisation of POMS as a value-added adsorbent for copper sequestration is highly desirable as a means for solid waste reduction. Therefore, this research aimed to evaluate the adsorption performance of POMS towards copper pollutant comprehensively. Adsorption attributes of the POMS-copper system were investigated using batch experiments, followed by statistical modelling to establish the simultaneous interactive effects of param-eters and to optimise the system. POMS was determined to exhibit 9.72 point of zero charge, with a rough surface containing pore sizes within 1-7 mu m and functional groups such as hydroxyl interacted with the copper. The statistically optimised adsorption capacity (15.84 mg g(-1)) was attained at 0.3 g POMS dosage, pH 4.56, 200 mg L-1 concentration and 60 min. The regeneration ability of POMS was satisfactory up to 5 adsorption-desorption cycles. Equilibrium and kinetic adsorption data were modelled based on the sum of normalised error (SNE) approach. The adsorption equilibrium was well represented by the Langmuir model (SNE: 3.69), with 16.56 mg g(-1) Langmuir maximum adsorption capacity at 30 degrees C. Adsorption kinetics studies revealed that the pseudo-second-order kinetic (SNE: 2.98) was the most appropriate model, with copper ions chemisorbed onto POMS surface via multiple mechanisms such as boundary layer and intraparticle diffusion. The new POMS-copper system was thermodynamically exothermic (Delta H degrees:-12.72 to -4.25 kJ mol(-1)) and spontaneous (Delta G degrees:-19.07 to -11.44 kJ mol(-1)). Conclusively, POMS was an effective, low cost and eco-friendly adsorbent for the removal of toxic copper from aqueous environment.