ICACT 2019

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Study of the Effect of Incorporating a Preconditioning Step for the Adsorption of Methylene Blue from Water by Douglas fir Biochar
(4th International Conference on Advances in Computing and Technology (ICACT ‒ 2019), Faculty of Computing and Technology, University of Kelaniya, Sri Lanka, 2019) Nawalage, S.; Kaumini, G.; Gunatilake, S.R.
Three major kinetic processes governing adsorbate uptake by an adsorbent such as biochar (BC) has been defined as external mass transfer, intraparticle diffusion (IPD) and mass action. In the usual methodology of batch adsorption, where the solution containing the adsorbate is directly introduced to the dry biochar, the entire pore space may not be accessible as the pore interior is not well hydrated. The presented work evaluates the effect of incorporating a preconditioning step where the BC is shaken with a selected organic solvent as a means of hydrating the hydrophobic pore interior. It is followed by its equilibration with de-ionized (DI) water to replace the preconditioning solvent. The process provides a BC with hydrated pores with a ‘sample like’ solvent. Solvents utilized for preconditioning were methanol (MEOH), acetone (ACE), acetonitrile (ACN) and DI followed by equilibration with DI. Sorption characteristics of pre-conditioned BC (PBC) was compared with that of non-preconditioned (NBC). The adsorption process was not significantly influenced by pH variations and the predominant sorption mechanisms were concluded to be π-π electron donor acceptor (EDA) interactions and pore filling. Adsorption capacity showed a stochastic dependence with increasing contact time for the preconditioned biochar in contrast to the NBC. Both PBC and NBC fitted well with the PSO behavior. Sorption capacities for all PBC were lower than NBC which can be attributed to pore blockage. In contrast to NBC, a clear rate determining step was not observed by the intraparticle diffusion model for PBC. Though the Freundlich isotherm model was fitted well by the NBC, the PBC sorption did not fit into the isotherm models studied such as Langmuir, Freundlich, Temkin, Sips and Redlich- Peterson. An enhancement in kinetics for DI PBC was observed at the compromise of ill-fitting isotherm patterns and uptake behavior.
A Novel Technique to Digest Biochar for Metal Analysis
(4th International Conference on Advances in Computing and Technology (ICACT ‒ 2019), Faculty of Computing and Technology, University of Kelaniya, Sri Lanka, 2019) Wathudura, P.D.; Peiris, C.; Navarathna, C.; Kaumal, M.N.; Gunatilake, S.R.
Biochar (BC) is a low cost carbonaceous adsorbent material widely used for the removal of toxic metal ions from aqueous systems due to their highly porous nature and presence of various functional groups. Depending on the feedstock used to produce these carbonaceous materials, the trace metal content may vary. Various digestion techniques have been incorporated to analyze the metal content of BC though a proper method has not yet been established. This study was focused on finding a suitable method to totally digest the carbonaceous material and to evaluate the matrix effect. Both open vessel and microwave digestion methods were carried out for BC derived from tea waste, king coconut husk, Douglas fir and steam activated coconut shell biochar (CSBC) using mixtures of 69% nitric acid (NA), fuming nitric acid (FNA), 98% sulfuric acid (SA) and 30% hydrogen peroxide (HP) and their turbidity were measured. Lowest turbidities for open vessel digestions were observed for SA/HP mixture for low-temperature pyrolyzed BC with no external heating (2.04 – 7.90 FNU). Microwave digestions provided satisfactory turbidity levels for NA, NA/SA mixture, FNA and FNA/SA mixture for all types of carbonaceous material (1.58 – 20.97 FNU). The matrix effects were compared using cadmium, copper, lead and zinc using flame atomic absorption spectrophotometry. Digestion mixture containing only fuming nitric acid showed the lowest matrix effect for cadmium (1.2) for CSBC and copper (2.4) for CSBC while the mixture containing only nitric acid shows lowest matrix effect (7.6) for zinc with respect to Douglas fir BC. Recovery study confirmed the suitability of FNA as a suitable digestion mixture incorporated with microwave energy.
Sorptive Removal of Lead (II) from Aqueous Solution using Value Added Tea-Waste Biochar Produced Under DifferentTemperatures
(4th International Conference on Advances in Computing and Technology (ICACT ‒ 2019), Faculty of Computing and Technology, University of Kelaniya, Sri Lanka, 2019) Kavinda, K.D.T.; Peiris, C.; Gunatilake, S.R.
The removal of lead from aquatic systems using biochar (BC) derived from tea-waste was evaluated. The customized in-house method of BC production was incorporated slow pyrolysis at 300 ℃ (300BC), 500 ℃ (500BC) and700 ℃ (700BC). The different BC types were subjected to a nitric acid modification and magnetization. Results showed reduced adsorption capacities for nitric modified BC. Batch sorption experiments were conducted to evaluate the effect of pH, equilibrium time, associated kinetic models and the thermodynamic basis of lead uptake. For both Non-Modified Biochar (NBC) and Magnetized Biochar (MBC), an acceptable fit for the pseudo second order kinetic model with regression coefficients greater than 0.998 justified a chemisorption process. The dominant mechanism for 700BC can be considered as pore filling together with π electron sharing between the graphene rings and lead whereas sorption on 300BC was governed by electrostatic interactions. Adsorption isotherms modeled were Langmuir, Freundlich, Sips, Redlich- Peterson and Toth, out of which the results were seen to best fit Langmuir and Sips models. A maximum Langmuir capacity of 57.80 mg/g and 48.61 mg/ for 700NBC and 700MBC were obtained respectively. Positive enthalpies and free energies indicated a nonspontaneous and exothermic sorption. Magnetic modification decreased sorption capacities by 15.86 % but led to the easy removal of biochar after the sorption.

ICACT 2019

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