Chemical Treatment of Banana Blossom Peels Adsorbent as New Approach for Manganese Removal: Isotherm and Kinetic Studies

ABSTRACT


74
The rapid industrial development has increased water sources pollution (Ahmed et al. 2014). Disposal of 75 contaminants that include toxic sludge, solvents, and heavy metals from industrial activities into water bodies had 76 been reported to be 300-400 million tonnes annually (Singh et al. 2018). The number of polluted water sources 77 in Malaysia increases over time due to the uncontrollable waste disposal and effluent discharge from industry 78 (Marsidi et al. 2018). The waterworks company had alarmed the presence of heavy metals detected in river due 79 to discharged from industrial effluents (Zou et al. 2016). In steel production, manganese (Mn) had been widely 80 used and discharged in the industrial effluents. Mn is a trace metal that is found mainly as oxides, carbonates, and 81 silicates in many different minerals, with pyrolusite (manganese dioxide) as the most common naturally-occurring 82 form (Milatovic and Gupta, 2018). Mn can be found abundantly in the earth's crust and water sources, which exist 83 in a broad range of oxidation states and species in the water (Tobiason et al., 2016) 84 Upon oxidation, Mn becomes insoluble in water and change the colour of the water into brown-red 85 colour, making the water aesthetically unpleasant and unfit for drinking (Marsidi et al. 2018; Bouchard et al. in Malaysia and can be utilize to produce low-cost adsorbents. Banana plant particularly is widely planted and 103 used for many purposes. About 16% of the total fruit production encompass of banana making it the second largest 104 fruit produced worldwide with the highest of 32% produced fruit in Malaysia (Pathak et al. 2017).

105
Currently, the study on banana blossom as adsorbent for the removal of contaminant is limited.

128
The BBP powder is next dried in an oven at 60 o C ± 1 o C for 12 hrs (Surovka and Pertile 2017) until it dry and sieve 129 using standard 60 mesh sieve. The schematic representation of BBP adsorbent preparation is shown in Figure 1.

131
Field emission scanning electron microscope (FESEM) and Energy Dipersive X-ray (EDX) were used 132 to determine the surface morphology and elemental composition of BBP adsorbent. The functional groups in BBP 133 adsorbent were analysed using a Fourier transform infrared spectroscopy (FTIR). The FTIR spectrum was BBP pattern using Bruker D8 Advanced. X-rays of 1.5406 Å wavelength was generated by Cu Kα monochromatic 137 radiation. The BBP adsorbent was compressed in a cassette sample holder and the data was collected from 2θ = 138 20° -80° with sampling pitch of 0.02°.

139
The surface area, total pore volume, and pore diameter were measured by a Brunauer-Emmett-Teller

140
(BET) method based on nitrogen adsorption-desorption at 77K (Thermo Scientific surface area and pore analyser).

171
The Langmuir isotherm was assumed as monolayer adsorption of solutes onto an adsorbent surface. The

172
Langmuir isotherm equation is written as:

182
The Freundlich isotherm is more commonly known relationship to describe the non-ideal and reversible 183 adsorption. The Freundlich isotherm is presented by the following equation: Where qe is the adsorbed metal ion mass at equilibrium (mg/g), qt is the adsorbed metal ion mass at time t (mg/g),

207
K1 is the pseudo-first-order reaction rate constant (l/min). Meanwhile, the pseudo-second order kinetic model 208 assumes that chemical adsorption can be the rate limiting stage involving valence forces through sharing or where K2 is a constant that represents the pseudo-second order reaction rate equilibrium (g/mg min) (Fathi et al.

246
The functional groups detected in BBP adsorbent before and after manganese adsorption is shown in  Adsorption is a complex phenomenon that depend on various factors including the pore structure, size, and pore size distribution curves (inset) of BBP adsorbent is shown in Figure 6. Based on the IUPAC 280 classification, the isotherm for BBP adsorbent is classified as type 2 which is macropores (>50 nm). The pore size

334
adsorption occurs rapidly on the adsorbent's external surface, followed by a slower internal diffusion process, 335 which may be the rate-determining step. This is comparable with this study, where the rate of adsorption is fast in the first 10 minutes, until almost equilibrium due to quick occupancy of Mn ions onto the surface of BBP adsorbent

340
The effect of BBP dosage on the removal of manganese with the optimal initial Mn concentration of 20 mg/L, at 341 pH 7 is shown in Figure 7(c). The adsorbent dosage was employed from 0.1 g/L to 0.7 g/L and the experiments 342 were shaken for 150 minutes. The obtained findings indicate that as the adsorbent dose is raised, the efficacy of 343 Mn removal improves. The greatest Mn removal was 96% at the optimum adsorbent dosage of BBP (0.5 g/L).

344
High adsorbent dosage provides more active exchangeable adsorption sites. However, excessive adsorbent dosage

393
The isotherm results obtained in the present study can be concluded that the experimental data for