Utilization of Coconut Milk Processing Waste as a Low-Cost Mercury Sorbent

Abstract

Desiccated coconut waste sorbent (DCWS), a byproduct of coconut milk processing, was studied as a sorbent for Hg(II) sorption. Energy dispersive X-ray analysis indicated that the DCWS mainly contained C, N, and O, while the Fourier transform infrared measurements confirmed the existence of hydroxyl, carboxyl, and amine groups on the DCWS surface. The point of zero charge (pH pzc ) and cation-exchange capacity (CEC) values were 6.05 and 2.02 meq/100g, respectively. The batch equilibrium data were fitted well by the Langmuir isotherm model with a maximum sorption capacity, q max of 500 mg/g, while the kinetic sorption data were found to follow a pseudo-second-order kinetic model. A column sorption study showed that the sorption capacity increased and the breakthrough time decreased with the increase in the initial Hg(II) concentrations. The regeneration studies revealed that the DCWS could be regenerated and reused.

Assessment of Food Processing and Pharmaceutical Industrial Wastes as Potential Biosorbents: A Review

“…The rate of increase under highly acidic conditions (pH 2–4) was mostly higher than that observed at milder acidic conditions (pH 4–6) [6, 72, 84, 100–102, 104, 108, 125, 129, 130]. Under basic conditions (pH > 7), heavy metal uptake decreased with pH [100, 101, 108]. Under severe acidic conditions, the very low reported uptake capacities were attributed to the fact that H + ions compete with the metal ions on the active sites [72, 101, 126] which indicates that biosorption is governed by electrostatic interactions under these conditions.…”

“…For heavy metal sorption, it was found that the increase in pH increases uptake capacity of heavy metals such as Cd, Pb, Ni, Cu, and Zn in both the acidic and the neutral range (pH 2–7). The rate of increase under highly acidic conditions (pH 2–4) was mostly higher than that observed at milder acidic conditions (pH 4–6) [6, 72, 84, 100–102, 104, 108, 125, 129, 130]. Under basic conditions (pH > 7), heavy metal uptake decreased with pH [100, 101, 108].…”

“…On the other hand, the uptake capacity decreases probably due to decrease in surface area that might be a result of having some of the sorption sites aggregated and overlapped [100, 102, 108, 129]. In a few cases, the removal reaches a peak value then declines [82, 101, 119] and this could be due to saturation of active sites.…”

“…In most studies, dynamic capacity was lower than its batch counterpart; and the same held true for % removal [100–102, 104, 131]. Column dynamics vary with column dimensions and flow rate.…”

Silver Ion Adsorption using Alkali and Organosilane Modified Coconut Pith Biosorbents

“…Biomaterials such as bacteria, fungi, algae, industrial wastes (e.g., food/beverage wastes, fermented wastes, anaerobic sludge, and activated sludge), agricultural wastes (e.g., fruit/vegetable wastes, rice residues, and palm oil residues), and natural residues (e.g., plant residues, saw dust, and tree bark) have been widely studied as biosorbents to treat wastewater containing organic and inorganic pollutants such as dyes, antibiotics, pesticides, and heavy metals Bhatnagar and Sillanpaa 2010;Demirbas 2008;Hasfalina et al 2010;Johari et al 2013;Macías-García et al 2012;Park et al 2010;Song et al 2013). The use of agricultural residues as alternative biosorbents for replacing the conventional adsorbents has also been widely studied.…”