Abstract
This study reported Nepenthes rafflesiana pitcher (NP) and Nepenthes rafflesiana leaves (NL) as new adsorbents for methyl violet (MV) dye. The experiments were done using 2 h contact time and without any pH alteration (pH 4.4). The effects of pH and ionic strength revealed hydrophobic–hydrophobic interaction as the predominant force of dye interaction with the adsorbent. Both NP-MV and NL-MV followed pseudo-second-order model indicating the adsorption processes may be governed by chemical process. Weber–Morris intraparticle diffusion model verified that the rate-limiting step of both the NP-MV and NL-MV systems is not intraparticle diffusion. The Langmuir model best described the adsorption process with high maximum monolayer adsorption (qm) of 288.7 and 194.0 mg g−1 for NP-MV and NL-MV, respectively. Thermodynamics studies revealed both NP-MV and NL-MV systems are spontaneous and endothermic in nature. From the regeneration study, it was found that NP’s and NL’s adsorption capacities could be recovered using distilled water and base whereby distilled water was able to recover 78% (NP) and 71% (NL) while base was able to recover 82% for both samples after three regeneration cycles.
Highlights
The industrialisation and urbanisation of nations sometimes sacrifice the environment for short-term economic gains
This study reported Nepenthes rafflesiana pitcher (NP) and Nepenthes rafflesiana leaves (NL) as new adsorbents for methyl violet (MV) dye
The effects of pH and ionic strength revealed hydrophobic–hydrophobic interaction as the predominant force of dye interaction with the adsorbent. Both NP-MV and NL-MV followed pseudo-second-order model indicating the adsorption processes may be governed by chemical process
Summary
The industrialisation and urbanisation of nations sometimes sacrifice the environment for short-term economic gains. Textile industry is a very water-intensive industry and is ranked as top ten most polluting industry in respect to water pollution (Kant 2012; Rasul et al 2006). Many dye wastewater methods have been innovated and improved. To name a few remediation methods, there are adsorption, phytoremediation (Kooh et al 2016a), photocatalyst (Saravanan et al 2013) and nanoparticles (Agarwal et al 2016). The cost of wastewater remediation by adsorption depends on the type of adsorbents. To ensure economic feasibility of the wastewater remediation process, one may choose materials that are renewable, sustainable, abundantly available or materials with little values such as agricultural wastes (Gupta and Nayak 2012; Kooh et al 2016b) and weeds (Lim et al 2014). Activated carbon may have been ideal materials for certain dyes and heavy metals; to produce them may be energy intensive
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