Silica Extraction From Beach Sand for Dyes Removal: Isotherms, Kinetics and Thermodynamics

Abstract

Beach sand is an abundant natural resource that contains silica minerals with many benefits. One of the uses of silica is to remove synthetic dyes that are toxic to biota in the environment. The goal of this research was to extract and characterize the silica from Bengkulu beach sand and to apply it as dyes adsorbent. The extraction of silica consisted of two steps that were potassium silicate formation and gel formation. The gel was formed by adding strong acid into a potassium silicate solution. Silica's particle size and crystallinity were characterized using PSA and XRD, respectively. SEM-EDS was used to characterize the morphology and chemical composition of extracted silica. The effect of the different experimental settings, like pH, temperature, contact time, the concentration of dyes and adsorbent weight, on adsorption of dyes were monitored as well as the study of adsorption isotherms, kinetics, and thermodynamics. At equilibrium, synthetic dyes adsorption to silica suited to the Freundlich model producing correlation coefficients (R 2 ) of 0.853 and 0.976 for remazol blue and congo red, respectively. At optimum conditions, maximum adsorption capacities for remazol blue and congo red were 133 and 131 mg/g, respectively. The research implied that adsorption of dyes to silica fitted the pseudo-second-order model with thermodynamic values of ∆G°, ∆H°, and ∆S° were -4.04 to 2.19 kJ/mol, -13.53 to -4.726 kJ/mol, and 0.019 to 0.021 J/mol.K, respectively. By using these results, we resolve that the adsorption of dyes trends was exothermic and spontaneous. In addition, the reaction increases the system's entropy. This study emphasizes the potential of silica from the sand beach as a substitute economical adsorbent for the toxic dyes removal.

Application of Gold Silica Nanocomposites in Electrochemical Biosensors: A Review

“…According to Firdaus et al (2020), to obtain silica nanoparticles, extraction methods from natural sand can be obtained. The beach sand is filtered using a 100 mesh sieve followed by immersion in acid to remove unwanted minerals other than silica.…”

“…Addition of base and heating for the alkaline fusion reaction with the K2SiO3 product. Filtration and addition of acid to obtain a white gel, then filtered, made the pH neutral and dried (Firdaus et al, 2020) Previsous research by Eddy et al (2015), powder silica particles with a sieving machine obtained 325 mesh then soaking with acid, washing until there is no yellowish color. Drying at 110° C and reacted with alkaline, then filtered and allowed to stand the gel for 18 hours.…”

Photocatalytic Phenol Degradation by Silica-Modified Titanium Dioxide

“…The results showed a fairly good percentage reduction of 93.77% and 93.55% for Cr(VI) and Pb(II), respectively. Furthermore, the silica successfully extracted from Bengkulu beach sand, Indonesia, using a potassium hydroxide (KOH) solvent, reached 90%, with a purity of 99.5% [23], while using a sodium hydroxide (NaOH) solvent, the purity was 97.3% [24]; the purity of silica obtained from Palangkaraya beach sand, Indonesia, was 91.19% [19].…”

Synthesis of Titanium Dioxide/Silicon Dioxide from Beach Sand as Photocatalyst for Cr and Pb Remediation

“…Eddy et al [9] extracted silica successfully from Palangkaraya beach sand, Indonesia with a benefit of 91.19% and Munasir et al [10] extracted silica successfully from Tuban beach sand, Indonesia, reaching 98.9% gain. In addition, Ishmah et al [11] and Firdaus et al [12] have succeeded in extracting silica from Bengkulu beach sand, Indonesia, by 97.3% and 99.5%, respectively. In this research, we evaluated the extraction of silicon dioxide (SiO 2 ) from beach sand precursors and subsequently composite with titanium dioxide (TiO 2 ) as a photocatalyst for decreasing the concentrations of Cr(VI) and Pb(II).…”