title: Lignocellulosic-derived modified agricultural waste: development, characterisation and implementation in sequestering pyridine from aqueous solutions.
abstract: The development and characterisation of modified agricultural waste (MAW) by H3PO4 activation is addressed in this study for sequestering pyridine from aqueous solutions. The adsorbent is characterised by carbon, hydrogen and nitrogen content of 55.53%, 3.28% and 0.98% respectively. The adsorbent also shows acidic (carboxylic, lactonic, phenolic groups) and basic carbon surface functionalities, functional groups viz. hydroxyl, carboxylic acid and bounded water molecules, BET surface area of 1254.67 m(2) g(-1), heterogeneous surface morphology and graphite like XRD patterns. Adsorption of pyridine is executed to evaluate the adsorptive uptake in batch (q(e)=107.18 mg g(-1)) as well as in column system (q(e)=140.94 mg g(-1)). The adsorption process followed the pseudo-second-order kinetics with the Langmuir isotherm best representing the equilibrium adsorption data. The thermodynamic parameters (ΔH(o)=9.39 kJ mol(-1), ΔG(o)=-5.99 kJ mol(-1), ΔS(o)=50.76 J K(-1) mol(-1)) confirm the endothermic and spontaneous nature of the adsorption process with increase in randomness at solid/solution interface. The adsorption mechanism is governed by electrostatic and π-π dispersive interactions as well as by a two stage diffusion phenomena. Thermally regenerated spent MAW exhibited better adsorption efficiency for five adsorption-desorption cycles than chemically regenerated. The low-cost of MAW (USD 10.714 per kg) and favourable adsorption parameters justifies its use in the adsorptive removal of pyridine.
authors.affiliation: Department of Chemistry, National Institute of Technology Silchar, Silchar 788010, India.
authors.forename: Md Juned K
authors.initials: MJ
authors.lastname: Ahmed
authors.affiliation: Department of Chemistry, National Institute of Technology Silchar, Silchar 788010, India. Electronic address: md_a2002@rediffmail.com.
authors.forename: M
authors.initials: M
authors.lastname: Ahmaruzzaman
authors.affiliation: Department of Chemistry, National Institute of Technology Silchar, Silchar 788010, India.
authors.forename: Ruhul A
authors.initials: RA
authors.lastname: Reza
mesh_terms: D000327:Adsorption; D000383:Agriculture; D003059:Cocos / Q000737:chemistry*; D008031:Lignin / Q000737:chemistry*; D010756:Phosphoric Acids / Q000737:chemistry*; D011725:Pyridines / Q000302:isolation & purification*; D055672:Static Electricity; D013816:Thermodynamics; D014866:Waste Products / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods
chemical_list: D010756:Phosphoric Acids; D011725:Pyridines; D014866:Waste Products; D014874:Water Pollutants, Chemical; C036909:lignocellulose; D008031:Lignin; C030242:phosphoric acid; C023666:pyridine
keywords: Adsorption; Adsorption mechanism; Modified agricultural waste; Pyridine; Thermodynamic parameters