Modified Rice Hull Research Articles

Supramolecular bioamphiphile facilitated bioemulsification and concomitant treatment of recalcitrant hydrocarbons in petroleum refining industry oily waste

Bioremediation of real-time petroleum refining industry oily waste (PRIOW) is a major challenge due to the poor emulsification potential and oil sludge disintegration efficiency of conventional bioamphiphile molecules. The present study was focused on the design of a covalently engineered supramolecular bioamphiphile complex (SUBC) rich in hydrophobic amino acids for proficient emulsification of hydrocarbons followed by the concomitant degradation of total petroleum hydrocarbons (TPH) in PRIOW using the hydrocarbonoclastic microbial bio-formulation system. The synthesis of SUBC was carried out by pH regulated microbial biosynthesis process and the yield was obtained to be 450.8 mg/g of petroleum oil sludge. The FT-IR and XPS analyses of SUBC revealed the anchoring of hydrophilic moieties of monomeric bioamphiphilic molecules, resulting in the formation of SUBC via covalent interaction. The SUBC was found to be lipoprotein in nature. The maximum loading capacity of SUBC onto surface modified rice hull (SMRH) was achieved to be 45.25 mg/g SMRH at the optimized conditions using RSM-CCD design. The SUBC anchored SMRH was confirmed using SEM, FT-IR, XRD and TGA analyses. The adsorption isotherm models of SUBC onto SMRH were performed. The integrated approach of SUBC-SMRH and hydrocarbonoclastic microbial bio-formulation system, emulsified oil from PRIOW by 92.86 ± 2.26% within 24 h and degraded TPH by 89.25 ± 1.75% within 4 days at the optimum dosage ratio of SUBC-SMRH (0.25 g): PRIOW (1 g): mass of microbial-assisted biocarrier material (0.05 g). The TPH degradation was confirmed by SARA fractional analysis, FT-IR, 1H NMR and GC-MS analyses. The study suggested that the application of covalently engineered SUBC has resulted in the accelerated degradation of real-time PRIOW in a very short duration without any secondary sludge generation. Thus, the SUBC integrated approach can be considered to effectively manage the hydrocarbon contaminants from petroleum refining industries under optimal conditions.

Preparation of Water Repellent Layer on Glass Using Hydrophobic Compound Modified Rice Hull Ash Silica

In this study water repellent layered glass has been prepared by coating silica (SiO2) combined with a hydrophobic silane compound. SiO2 was extracted from rice hull ash and two silane compounds, namely hexadecyltrimethoxysilane (HDTMS) and trimethylchlorosilane (TMCS) were used. Coating was performed through two deposition techniques, i.e. one step (mono-layer) and layer by layer (LBL, multi-layer). The effect of silane to SiO2 mole ratio, silane type and layer number on the glass characters was evaluated. Characterization included hydrophobicity, transparency, surface roughness and stability of coating. Results showed that increasing the mole ratio of silane to SiO2 and the layer number increased the hydrophobicity of the glass surface. The optimum mole ratio was 5:1 and the significant increase of contact angle occurred at lower mole ratio, but the stability tends to be increased at higher mole ratio. For HDTMS-SiO2 layer, the technique of LBL technique produced a coating with higher hydrophobicity and transparency than single-stage one. The LBL technique produced the highest water contact angle of 103.7° with transmittance of 96%, while for TMCS-SiO2 layer the one stage technique produced hydrophobic layer with higher water contact angle of 108.0° and transparency about 94.52%. The prepared hydrophobic glasses were relatively stable in polar and non-polar solvents, but unstable to ambient conditions.

Coating of magnetite with mercapto modified rice hull ash silica in a one-pot process.

In this research, mercapto-silica coated magnetite (Fe3O4-SiO2-SH) has been prepared in aqueous solution through a simple approach so called a one-pot process. The Fe3O4-SiO2-SH was prepared in nitrogen condition by mixing magnetite, 3-mercaptopropyltrimethoxysilane (MPTMS), and sodium silicate (Na2SiO3) solution extracted from rice hull ash, and adjusting the pH of 7.0 using hydrochloric acid. The residue was washed with deionized water, dried at 150°C and separated with an external magnetic field. In that work, the volume of MPTMS and Na2SiO3 was varied and the total amount of Si represented as silica was kept constant. Characters of the material including the functional group presence, the structure, the porosity, the morphology and stability toward various solvents were identified and evaluated. Results of characterization indicated that mercapto-silica has been coated magnetite particle with a simple one-pot process. Coating mercapto-silica on magnetite increases particle size, surface area, and chemical stability. Additionally, Fe3O4-SiO2-SH also shows high stability toward various organic solvents. The magnetic property of magnetite does not change after coating and the addition of nonmagnetic material still gives high value of maximum saturation magnetization. The presence of mercapto groups effective for interaction with heavy metal ions, the high chemical stability without removing the magnetic property promises the prospective application of Fe3O4-SiO2-SH in the future such as for separation and removal of heavy metal ions from aquatic environments.

Adsorption of Au(III), Cu(II) and Ni(II) on Magnetite Coated with Mercapto Groups Modified Rice Hull Ash Silica

Adsorption of Au(III), Cu(II) and Ni(II) on Magnetite Coated with Mercapto Groups Modified Rice Hull Ash Silica

Oxalic Acid Modified Rice Hull as a Sorbent for Methylene Blue Removal

The potential of oxalic acid modified rice husk (ORH) to adsorb Methylene Blue (MB) from aqueous solution was investigated under various experimental conditions. Parameters studied included pH, initial dye concentrations, contact time, sorption isotherm, agitation rate and adsorbent dosage. A comparison study on the percentage uptake of natural rice husk and oxalic acid modified rice husk on MB dye showed that oxalic acid modified rice husk gave better removal efficiency. The percentage of dye uptake increased with increasing of pH and contact time. The optimum pH for MB removal was recorded at the range of pH 4 to pH 10 and the adsorption equilibrium was achieved after the first one and a half hours of contact time. From the kinetic study, the adsorption process correlated well with pseudo-second order kinetics equation. The experimental data were fitted into different isotherm model equations and the results revealed that the system under studied is better explained by Langmuir isotherm as compared to Freundlich isotherm. The maximum sorption capacity of ORH for MB was 29.15mg/g.

Basic and Reactive Dyes Sorption Enhancement of Rice Hull through Chemical Modification

Problem statement: Many studies have been conducted on the removal of either anionic or cationic dyes. However, as a mixture of dyes does commonly exist together in wastewater, therefore it is of great interest to have a material that can remove both types of dyes. Approach: To prepare an inexpensive and efficient sorbent by chemically modifying rice hull for the removal of both basic and reactive dyes. Different chemical modifications were performed on rice hull and a comparison study on the uptake of dyes was carried out. Optimization study was carried out on most promising modified rice hull. Surface morphology of modified rice hull was examined and the functional groups present were determined using FTIR. Results: From the results, it appeared that by using EDA modified rice hull, an appreciable amount of both dyes could be sorbed. Varying the EDA/NRH ratios and heating temperatures affected the uptake of BB3 and RO16. The investigated sorbents were non-porous materials, due to the absence of pores and cavities. Sorption-desorption study showed that a complete recovery of BB3 can be obtained using high concentrations of H2SO4 and HCl but the desorption experiments of RO16 using NH3 and NaOH were not successful. Conclusion: The modification of rice hull with EDA under the optimum conditions (in a ratio of 1.00 g of NRH to 0.02 mole of EDA in a well stirred water bath at 80°C for 2 h) resulted in the formation of a sorbent (MRH) that could be used successfully to remove Both Basic (BB3) and Reactive dyes (RO16).

Tartaric Acid Modified Rice Hull as a Sorbent for Methylene Blue Removal

Problem statement: Improper dye discharge from various industries such as textile, paper, cosmetic and plastics into receiving streams can be one of the sources towards water pollution. The release of these effluents not only causes various disruptions in the ecosystems, but also poses hazard effect as most of the dyes are highly toxic, mutagenic and carcinogenic in nature. Approach: To prepare an inexpensive and efficient sorbent by chemically modifying rice hull for the removal of Methylene Blue (MB) which is predominantly used in coloring acrylic fiber. Batch experiments were carried out for the removal of MB from aqueous solution by using Tartaric Acid Modified Rice Hull (TARH). Parameters studied include effect of pH, contact time, initial dye concentration and agitation rate and sorption isotherm. Results: From the results, the percentage uptake of MB increased with increasing contact time and agitation rate. Based on the linear regression correlation coefficient, R2, the system under study is more appropriately described by the pseudo-second order model. Maximum sorption capacity calculated from the Langmuir model is 25.0 mg g-1 for MB. Conclusion: The study has shown the effectiveness of TARH in the removal of MB, a basic dye from synthetic solutions.

Selectivity of the Cd2+/Ca2+ exchange on modified rice hull silica

The rice hull ash is composed by 94% of SiO2, an agricultural waste that can be recovered and purified by a depolymerization reaction yielding an organo‐silicic gel. The purpose of this paper is to show that this silica can be used to fix Cd2+ from aqueous solution. The pH of hydrolysis of the organo‐silicic gel is the main factor modifying the distribution between the solid and the solution. The contact time between the Cd2+ solution and the solid was studied to optimize the sorption conditions. The equilibrium measurements were performed after 40 hours at room temperature. The competition with Ca2+ ions in the solutions was also studied in order to evaluate the selectivity of the Cd2+ fixation. It was found that the rice hull ash has a higher capacity to fix Cd2+ than the rice hull derivatives.

Ethylenediamine modified rice hull as a sorbent for the removal of Basic Blue 3 and Reactive Orange 16

The potential of ethylenediamine modified rice hull to remove both basic and reactive dyes from aqueous solutions was studied. Equilibrium sorption data could be fitted into Langmuir and Brunauer-Emmett-Teller isotherm models. Sorption was enhanced by 4.5- and 2.4-fold for Basic Blue 3 and Reactive Orange 16, respectively, in binary dye solutions compared to single dye solutions. Column studies revealed that breakthrough was bed-depth, flow-rate and influent-concentration dependent. Unusual breakthrough curves were obtained for Reactive Orange 16, with very rapid initial breakthrough followed by complete retention at low flow rate, influent concentration and high bed depth. The breakthrough curves of Basic Blue 3 followed the typical S shape of packed-bed systems. Theoretical breakthrough curves at different bed depths and flow rates generated by the two-parameter mathematical model agreed well with the experimental data of single dye solution of Basic Blue 3.

Removal of basic and reactive dyes using ethylenediamine modified rice hull

Wastewaters from textile industries may contain a variety of dyes that have to be removed before their discharge into waterways. Rice hull, an agricultural by-product, was modified using ethylenediamine to introduce active sites on its surface to enable it to function as a sorbent for both basic and reactive dyes. The sorption characteristics of Basic Blue 3 (BB3) and Reactive Orange 16 (RO16) by ethylenediamine modified rice hull (MRH) were studied under various experimental conditions. Sorption was pH and concentration dependent. Simultaneous removal of BB3 and RO16 occurred at pH greater than 4. The kinetics of dye sorption fitted a pseudo-second order rate expression. Increase in agitation rate had no effect on the sorption of BB3 but increased uptake of RO16 on MRH. Decreasing particle size increased the uptake of dyes in binary dye solutions. Equilibrium data could be fitted into both the Langmuir and Freundlich isotherms. Maximum sorption capacities calculated from the Langmuir model are 14.68 and 60.24 mg/g for BB3 and RO16, respectively in binary dye solutions. This corresponds to an enhancement of 4.5 and 2.4 fold, respectively, compared to single dye solutions. MRH therefore has the potential of being used as an efficient sorbent for the removal of both dyes in textile wastewaters.

Sorption of Cr(VI) and Cu(II) in aqueous solution by ethylenediamine modified rce hull

The sorption characteristics of Cr(VI) and Cu(II) by ethylenediamine modified rice hull from single and binary metal ion solutions were evaluated under various experimental conditions. Optimal Cr(VI) and Cu(II) removal from single metal ion solutions occurred at pH 2.0 and 5.5, respectively. Simultaneous removal of Cr(VI) and Cu(II) occurred at pH greater than 3.0. The sorption kinetics of Cr(VI) and Cu(II) from single and binary metal ion solutions were studied with reference to metal concentration, agitation rate and particle size. Sorption of Cr(VI) was more rapid than Cu(II). The kinetics of metal ion sorption fitted a pseudo‐second order expression. The variation in the initial uptake rates was very small at an agitation rate beyond 150 rpm and sorption was generally independent of particle size. Equilibrium sorption data could be fitted into the Langmuir isotherm equation. Maximum sorption capacities of ethylenediamine modified rice hull for Cr(VI) at pH 2 and Cu(II) at pH 4 in single metal solutions were 0.45 and 0.06 mmol g−1, respectively. This corresponds to an enhancement factor of 2.6 and 3 fold for Cr(VI) and Cu(II), respectively, compared to natural rice hull. A synergistic effect was observed for sorption of these ions in binary metal solutions.

Sorption enhancement of phosphorus by chemically modified rice hull

Chemically modified rice hull was prepared through a single stage chemical reaction with N‐(3‐chloro‐2‐hydroxypropyl)‐trimethylammonium chloride. The sorption characteristics of this material were studied under batch and continuous flow conditions. Parameters investigated under batch conditions were different initial concentrations, agitation rates, temperature and the interfering effect of other anions. Maximum sorption of P(V) calculated from Langmuir isotherm model was 9.53 mg/g and this value is higher than that of unmodified rice hull which could sorb only 0.23 mg/g of P(V). Under continuous flow conditions, it was found that the time for 50% breakthrough showed a linear relationship with bed‐depth although it did not obey the Hutchin's bed‐depth service time model.