Synthesis of Clay Derived Nanosilicates Impregnated With Prosopis Juliflora Biochar for Removal of Selected Heavy Metals in Water
Abstract
Due to growing urbanization, population growth, and industrial activity, heavy metals are now
entering water bodies at a faster pace. The current treatment methods are ineffective, and this has
detrimental effects for both human health and the environment. The research reports the
synthesis of clay-derived nanosilicates that has been fused with biochar from Prosopis Juliflora.
The effectiveness of the synthesized materials in removing heavy metals from water was then
evaluated. Elemental analysis and characterization of the nanosilicates revealed the composition
of silicates at 83.6% in the extract with 20% (w/v %) NaOH as extracting media gave the best
with the best result. The FTIR characterization depicted a typical structure for sodium silicates
with IR bands of 1000, 1500, 1700, and 3500 cm-1 describing silicate bands. Nanosilicates with
an average diameter of 85 nm that are agglomerated and round in shape were successfully
synthesized, as demonstrated by the morphological analysis performed using SEM and TEM.
Phase analysis with XRD displayed broadband at 2θ=30o depicting the presence of silicate
nanoparticles with intense peaks from 25.26o to 65.93o which is usually related to silicate
nanoparticles. The characterization of biochar biomaterial prepared through pyrolysis showed
elemental composition mainly of carbon and oxygen atoms when characterized by XRF and
EDX. The FTIR spectra showed O-H stretching at 3500 cm-1 and a peak at 1600 cm-1 ascribed to
carboxylate (COO-1) which is consistent with bands of most biochars. The XRD pattern of
Prosopis biochar material showed a rise in the background level of between 11o and 13o
absorption bands which is consistent with the existence of cellulose and other related organic
compounds. A narrow sharp peak seen at 30o was attributed to amorphous carbon. The SEM
analysis revealed key morphological patterns of fibrous structure and pith. The biochar sample
depicted uneven particles of different dimensions with vascular features filled in rolls with a
comparatively uniform surface as observed in the literature for most biochars. Elemental analysis
of nanocomposite material of biochar and clay silicates using EDX revealed the main
composition of carbon, oxygen, silica, aluminum, and iron. The FTIR spectra revealed a broad
peak at 3500 cm-1 suggesting O-H stretching, a second peak at 2350 cm-1 relating to CO2
absorption, and a peak at 1063 cm-1 denoting C-O stretching vibration. XRD phase analysis of
nanocomposite showed mineral crystal existence with peaks at 19.9o, 25o, and 35o identified as
phyllosilicates which means successful impregnation of silicates on carbon surfaces of biochar.
The SEM images and EDX revealed high peaks of silicon, aluminum, titanium, and iron a typical
composition of clay minerals. The efficiency of each synthesized substance in the elimination of
heavy metals from water was evaluated using batch adsorption. Clay silicates (99.2 %), Biochar
(99.5 %) and composite material (99.4 %) had very good effectiveness of removal of the selected
heavy metals but biochar material had the highest efficacy level. The kinetic experiments using
Langmuir and Freundlich isotherms indicated a second-order kinetic model fit with data giving a
straight line and better correlation r2 correlation of coefficient of 0.999.
Publisher
University of Nairobi
Rights
Attribution-NonCommercial-NoDerivs 3.0 United StatesUsage Rights
http://creativecommons.org/licenses/by-nc-nd/3.0/us/Collections
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