Petal (Parkia Speciosa) pod as adsorbent for removal of congo red dye

Fruit and vegetable wastes which are produced abundantly from agricultural industries in Malaysia frequently causes nuisance in municipal landfills. Thus, biosorption by these waste-based adsorbents can be utilised as a cost saving method for the removal of dyes from wastewater. Dyes that being released into aquatic environment not only causes pollution but also brings adverse effect to human health, aquatic life and destroy beautiful nature of water. The use of petai pod (Parkia speciosa) as an adsorbent to remove dyes from effluents have not been widely ventured yet, therefore the objective of this study is to utilise this agricultural waste to remove Congo red dye from aqueous solution. The effect of various operational parameters such as adsorbent size (0.125, 0.300 and 0.710 mm), adsorbent dosage (0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 g), initial dye concentration (20, 50, 100, 150, 200, and 300 mg/L), contact time (0.5, 1, 2, 4, 8, 16, and 24 hours) and pH (1 - 10) were studied. The study showed that up to 98.04 % of Congo red removal can be achieved under optimum condition (adsorbent size: 0.125 mm, adsorbent dosage: 2.0 g, initial dye concentration: 150 mg/L, contact time: 1 hour and pH: 3). The equilibrium data was analysed using Langmuir and Freundlich isotherms to disclose the degree of adsorption favourability. The best-fitted data was obtained in Langmuir model with a maximum adsorption capacity of 5.263 mg/g. The raw and Congo red stained petai pod were characterised by using FTIR, SEM, and XRF methods. FTIR analysis showed raw and dye stained petal pod have prominent peaks of 0-H group, C-H group, C=C group and C-0 group. SEM micrographs showed raw petai pod have a lot of spaces and after dye adsorption, these spaces were filled by the dye molecules. XRF analysis showed that the highest element in raw petal pod is aluminium (95.4%).