Characterization of Adsorbent Developed from Rice Husk: Effect of Surface Functional Group on Phenol Adsorption

From Ficus recemosa Leaf Galls to Therapeutic Silver Nanoparticles: Antibacterial and Anticancer Applications

The synthesis of silver nanoparticles (AgNPs) using environmentally friendly methods has become increasingly important due to its sustainability and cost-effectiveness. This study investigates the green synthesis of AgNPs using gall extracts from the plant Ficus recemosa, known for its high phytochemical content. The formation of AgNPs was verified through multiple analytical techniques, including UV-Vis spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), zeta potential analysis, and dynamic light scattering (DLS). The UV-Vis spectroscopy results displayed a distinct surface plasmon resonance peak indicative of AgNP formation. FTIR analysis revealed specific interactions between silver ions and phytochemicals in the gall extract, while TEM images confirmed the nanoscale morphology and size of the synthesized particles. Zeta potential and DLS analyses provided insights into the stability and size distribution of the AgNPs, demonstrating good colloidal stability. Biological properties of the AgNPs were assessed through various assays. Antimicrobial activity was tested using the disc diffusion method against Escherichia coli and Staphylococcus aureus, showing significant inhibitory effects. The anticancer potential was evaluated using the trypan blue exclusion assay on Dalton's Lymphoma Ascites (DLA) cells, revealing considerable cytotoxicity. Additionally, antimitotic activity was studied in the dividing root cells of Allium cepa, where the AgNPs significantly inhibited cell division. This research highlights the effective use of F. recemosa gall extracts for the green synthesis of AgNPs, presenting an eco-friendly approach to producing nanoparticles with strong antimicrobial, anticancer, and antimitotic properties. The promising results suggest potential applications of these biogenic AgNPs in medical and agricultural sectors, paving the way for further exploration and utilization.

Improving adsorption performance of L-ascorbic acid from aqueous solution using magnetic rice husk as an adsorbent: experimental and RSM modeling

In this research, rice husk (RH) was utilized to prepare a magnetic adsorbent for adsorption of ascorbic acid (AA). The magnetic agent is iron(III) chloride (FeCl₃). The impact of acid concentration in the range of 400-800 ppm, adsorbent dosage in the range of 0.5-1 g, and contact time in the range of 10-130 min were studied. The Langmuir model had the highest R² of 0.9982, 0.9996, and 0.9985 at the temperature of 15, 25, and 35 °C, respectively, and the q_max values in these temperatures have been calculated at 19.157, 31.34, and 38.75 mg/g, respectively. The pseudo-second-order kinetic model had the best agreement with the experimental results. In this kinetic model, the values of q have been measured at 36.496, 45.248, and 49.019 mg/g at the acid concentration of 418, 600, and 718 ppm, respectively. The values of ΔH^o and ΔS^o were measured 31.972 kJ/mol and 120.253 kJ/mol K, respectively, which proves the endothermic and irregularity nature of the adsorption of AA. Besides, the optimum conditions of the design-expert software have been obtained 486.929 ppm of acid concentration, 0.875 g of the adsorbent dosage, and 105.397 min of the contact time, and the adsorption efficiency in these conditions was determined at 92.94%. The surface area of the RH and modified RH was determined of 98.17 and 120.23 m²/g, respectively, which confirms the high surface area of these two adsorbents.

Photodegradation of Methylene Blue with Aid of Green Synthesis of CuO/TiO2 Nanoparticles from Extract of Citrus Aurantium Juice

Green synthesis methods using plants have many advantages such as time-saving, chemical-free, and negative effects on the environment. So, extracted Citrus aurantium juice was used to synthesize green CuO/TiO2 and(G- CuO/TiO2) nanocatalyst which was characterized by XRD, SEM, EDX, FTIR, BET, and ZP and utilized in the degradation of methylene blue (MB) under UV lamps and dark environments. The ANOVA program was used to maximize the photodegradation efficiency (%) of (G-CuO/TiO2) on the MB dye. The four independent variables: Initial dye concentration (10-50 mg/L), pH (3-9), adsorbent dose (200-1000 mg/L), and contact time (30-90 min) served to the model of the photodegradation efficiency (%). The ANOVA results confirmed the high significance of the regression model while the predicted values of the photodegradation efficiency (%) of MB were in good agreement with the corresponding experimental ones. Optimized conditions for the maximum photodegradation efficiency (98.6%) by (G- CuO/TiO2) NPs were the initial dye concentration (10.93 mg/L), pH (8.87), adsorbent mass (986.43 mg/L), and contact time (89.08 min). The validity of the quadratic model was examined, and found in good agreement with the experimental values. Results demonstrated that (G-CuO/TiO2) could be a promising photocatalyst in the degradation of MB dye. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Adsorption of Cd (II) Using Chemically Modified Rice Husk: Characterization, Equilibrium, and Kinetic Studies

Cadmium (Cd) is a highly toxic heavy metal considered carcinogenic to humans. The adsorption behavior of cadmium adsorption using untreated and chemically modified rice husk was investigated. Experimental tests were carried out to evaluate the influence of the variables pH, initial concentration of cadmium, and dosage of adsorbent in the adsorption process. In optimal experimental conditions, the maximum adsorption efficiency was 92.65%. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) were used allowing the identification of the main functional groups and morphology of rice husk and treated rice husk, and the results showed an improvement of adsorption characteristics after rice husk treatment with NaOH. The optimum adsorption pH for both types of rice husk was 7. The maximum adsorption capacities of RH and treated RH fitted by the Langmuir model were 5.13 mg/g and 11.06 mg/g, respectively. The pseudosecond order kinetics has the best coefficients of determination for untreated ( $R^2=0.992$ ) and treated ( $R^2=0.999$ ) rice husk. The adsorption process was found to be endothermic in nature with enthalpy of 14.08 kJ/mol and entropy of 170.98 J/mol.K. The calculated activation energy was 24 kJ/mol. The results showed the potential of rice husk as a low-cost, easily managed, and efficient biosorbent for Cd removal from waters.

Enhancement of Storage Stability and Masking Effect of Curcumin by Turmeric Extract-Loaded Nanoemulsion and Water-Soluble Chitosan Coating

This study focused on improving curcumin stability in various pHs and NaCl concentrations and reducing the strong scent of turmeric by the nanoemulsions system and further coating with water-soluble chitosan (WSC). Turmeric extract-loaded nanoemulsions (TE-NEs) were firstly prepared by mixing an oil phase containing turmeric extract, MCT oil, and lecithin, and an aqueous phase containing tween 80 using an ultrasonication method. TE-NEs were further coated with WSC in the ratio of TE-NEs and WSC (1:1 to 1:10). The optimum WSC-TE-NEs exhibited an average particle size of 182 nm, a PDI of 0.317, and a zeta potential of +30.42 mV when WSC-TE-NEs were prepared in the ratio of 1:1. The stability of the WSC-TE-NEs was also assessed by determining the remained curcumin content. The remained curcumin contents of the TE-NEs and the WSC-TE-NEs were higher than that of the turmeric extract (TE) at pH 2~7 and NaCl concentrations of 100~400 mM. Fourier transform infrared (FT-IR) spectra, transmission electron microscope (TEM), and confocal laser scanning microscope (CLSM) images confirmed that the TE-NEs were successfully encapsulated with a WSC coating. As a result of GC analysis, the content of aromatic-turmerone was significantly decreased in the TE-NEs and the WSC-TE-NEs compared to the pristine TE, but there was no significant difference between the TE-NEs and the WSC-TE-NEs. These results suggest that water-soluble chitosan-coated nanoemulsions may be suitable for improving the chemical stability and masking effect of curcumin to facilitate its application in food.

Rice Industry By-Products as Adsorbent Materials for Removing Fluoride and Arsenic from Drinking Water—A Review

In drinking water, high concentrations of fluoride and arsenic can have adverse effects on human health. Waste deriving from the rice industry (rice husk, rice straw, rice bran) can be promising adsorbent materials, because they are (i) produced in large quantities in many parts of the world, (ii) recoverable in a circular economy perspective, (iii) at low cost if compared to expensive conventional activated carbon, and (iv) easily manageable even in developing countries. For the removal of fluoride, rice husk and rice straw allowed to obtain adsorption capacities in the range of 7.9–15.2 mg/g. Using rice husk for arsenic adsorption, excellent results were achieved with adsorption capacities above 19 mg/g. The best results both for fluorides and arsenic (>50 mg/g) were found with metal- or chemical-modified rice straw and rice husk. Identifying the next steps of future research to ensure the upscaling of biochar from recovered by-products, it is fundamental to perform: (i) tests on real waters for multicomponent adsorption; (ii) experiments with pilot plants in continuous operation; (iii) cost analysis/real applicability of modification treatments such as metal coupling or chemical synthesis; (iv) more studies on the biochar stability and on its regeneration or recovery after use.

Revealing the heterogeneous activation mechanism of peroxydisulfate by CuO: the critical role of surface-binding organic substrates

Heterogeneous catalytic activation mechanisms of peroxydisulfate (PDS) by transition metal oxides are generally attributed to the interactions between catalysts and PDS, however, the role of the co-existed organic substrate was largely overlooked in the past studies. In this work, phenol was selected as the target organic pollutant in a CuO/PDS system to evaluate its deep-seated role in participating in the effective activation of PDS. First, optimized reaction conditions as pH of 6.0, CuO of 5.96 g·L^-1 and PDS of 2.5 mM were obtained by the response surface methodology (RSM) with a phenol degradation efficiency of 84.0%. It was further found that pre-adsorption of phenol or PDS led to obviously different performances in the phenol degradation with/without the radical scavengers. Two different activation pathways of PDS, i.e., the non-radical pathway mediated by surface deprotonated phenol to generate ¹O₂ and the radical pathway mediated by structural Cu(I)/Cu(II) to produce SO₄^-, were therefore proposed, and the former was predominant in the CuO/PDS/phenol system. In addition, HCO₃^- and HPO₄^2- could strongly inhibit the phenol degradation while Cl^- and NO₃^- only performed negligible effects. NaOH washing could regenerate the surface hydroxyl groups and recover the catalytic ability of CuO. The result of this study integrated the interactions among the catalyst, oxidant and substrate, providing new insights into environmental-friendly PDS activation processes.

Physicochemical and instrumental characterization of rice husk and its potential use as a low cost adsorbent for mutagenic dye bromophenol blue

In this study fine powder of rice husk were used as novel adsorbent for the removal of bromophenol dye. Different conventional physicochemical analysis and instrumental techniques were used to characterize the adsorbent. The surface area of the adsorbent was found to be 160.6 m2/g with bulk density of 1.139 g/dm3. Proximate and ultimate analysis showed that the selected material is a rich source of carbon with the advantage of not having Sulphur contents. FTIR and SEM analysis confirmed the surface modification via aqua regia in comparison to parental material (that have enhanced its surface porosity). The maximum uptake capacity (0.8 mg/g) of dye was reached at pH 3, 20 ppm of adsorbate concentration, and 0.5 g of treated rice husk dosage at room temperature and 60 min of equilibrium time. The equilibrium adsorption data was best explained by Freundlich adsorption isotherm with R 2 value of 0.998. Kinetic studies revealed that adsorption follows pseudo second order kinetic model with R 2 value of 0.997, K 2 equal to 0.831 (g/mg min), and q e value of 0.97 mg/g. The thermodynamic parameters (∆S° = 6.78 J/mol, ∆H° = 1501 J/mol, ∆G° −1.50, 0.5, 0.621 and 0.0787 kJ/mol corresponding to 293, 303, 313 and 333 K) pointed towards the endothermic and spontaneous nature of the process.

The Physical and Optical Studies of Crystalline Silica Derived from the Green Synthesis of Coconut Husk Ash

The green synthesis of silica has been extensively explored over the last few decades, as silica compounds found in commercial products can cause negative effects on human health. This calls for alternative ways to produce silica that are safer, cheaper and more environmentally friendly. Some of the agricultural wastes proven to contain silica include rice husk, sugarcane bagasse, coconut shells and coconut husk. This paper describes the synthesis of silica from coconut husk waste, and its physical and optical properties for potential utilization in optical applications. Coconut husk was subjected to fire at 500–700 °C so as to form coconut husk ash (CHA), and was then treated with sulfuric acid to extract silica from the ash. Most of the weight degradation subsequently occurred at temperatures from 221 to 360 °C. X-ray fluorescence (XRF) analysis proved that 91.76% of the silica was obtained, while major peaks on the X-ray diffraction (XRD) spectrum were observed after the acid treatment. Chemical bonds such as Si-O-Si, CH2, -OH and Si-OH were found in the spectrum of the Fourier transform infrared spectroscopy (FTIR). Furthermore, the particles displayed rod-like shapes and irregular sizes, but the particle with sizes ranging from 200–750 nm decreased after the acid treatment. The relationship between the absorption coefficient and photon energy was obtained by finding the optical energy gap, which was found to be 4.3 eV. These data points provide critical information when used in optical applications. The overall studies show that synthesized silica has great potential for use in optical field applications.

Catalytic activity of acid-treated biomass for the degradation of expanded polystyrene waste

Pyrolysis processes were investigated using expanded polystyrene waste (EPW) with a catalyst synthesized from rice husk (RH). Biomass was treated with different acids, i.e., sulfuric acid, oxalic acid, and hydrochloric acid. The effect of normality on the oxalic acid-treated catalyst and the effects of polymer to catalyst ratio on (i) oil, gas, and residues yields; (ii) temperature; and (iii) time for the complete reaction were investigated for the effective use of oil for fuel production. The catalyst treated with 0.25 N (RH_OA0.25) resulted in a high oil yield of 96 wt% and a residue yield of 3.47 wt%. The oil produced contained mainly aromatic compounds, which contributed 67.86% in an area-based GC-MS analysis. The synthesized catalyst showed a stable capacity for three regeneration runs. The significant factor is that the synthesized catalyst decreased the activation energy during the pyrolysis of EPW. Graphical abstract.

Evaluation of two different carriers in the biodegradation process of an azo dye

PURPOSE

The MBBR solution has been applied for the textile wastewater treatment. However, in order to develop cost-effective solutions, waste biomass can be used as carrier. Rice husks are agricultural waste which have been used as an adsorbent of dyes; besides, they can provide and sustain suitable microorganism communities for the degradation of dyes. This study aimed to evaluate the biodegradation of the azo dye Direct Red 75 in two treatment systems with different carriers.

METHODS

Bioreactor A was composed by an anaerobic bioreactor filled with Kaldnes K1 carriers employed in the MBBR technology and the study was performed in 2 different temperatures, 30 ± 0.5 °C and 21 ± 2 °C. Biofilter B was composed by a sequenced anaerobic-aerobic system with rice husks as carriers and this study was performed at 21 ± 2 °C. The rice husks was also employed as a source of microorganisms in both systems. Decolourization, surface area of the carriers and other parameters were analysed.

RESULTS

Biofilter B showed high rates of decolorization, mainly over 90% in all HRT tested (24, 48 and 12 h), presenting itself as a stable system, whereas Bioreactors A showed better performances with 48 h of HRT, about 85% for A at 30 ± 0.5 °C and 45% at 21 ± 2 °C. With a similar amount of carriers, analyses showed that rice husks had a much larger surface for microorganisms to grow on than Kaldnes K1.

CONCLUSION

The Biofilter B is a worthwhile system to be investigated and applied for the decolourization of textile wastewater treatment; for instance, in developing countries.

Carbonaceous Greenhouse Gases and Microbial Abundance in Paddy Soil under Combined Biochar and Rice Straw Amendment

Little is known about the carbonaceous greenhouse gases and soil microbial community linked to the combination of biochar (BC) and rice straw (RS) in paddy soils. The objectives of this research were to evaluate the effects of combining BC and RS on (1) CH4 and CO2 production from paddy soil, (2) archaeal and bacterial abundance, and (3) rice grain yield. The experiments consisted of a pot trial and an incubation trial, which had a completely randomized design. The experiments included five treatments with three replications: (a) the control (without BC, RS, and chemical fertilizer (CF)); (b) CF; (c) BC 12.50 t ha−1; (d) RS 12.50 t ha−1; and (e) combined BC 6.25 t ha−1 + RS 6.25 t ha−1 + CF. In the sole RS treatment, CH4 production (0.0347 mg m−2 season−1) and the archaeal and bacterial abundance (5.81 × 108 and 4.94 × 1010 copies g−1 soil dry weight (DW)) were higher than outcomes in the sole BC treatment (i.e., 0.0233 mg m−2 season−1 for CH4 production, and 8.51 × 107 and 1.76 × 1010 copies g−1 soil DW for archaeal and bacterial abundance, respectively). CH4 production (0.0235 mg m−2 season−1) decreased significantly in the combined BC + RS + CF treated soil compared to the soil treated with RS alone, indicating that BC lessened CH4 production via CH4 adsorption, methanogenic activity inhibition, and microbial CH4 oxidation through bacterial methanotrophs. However, the archaeal abundance (3.79–5.81 × 108 copies g−1 soil DW) and bacterial abundance (4.94–5.82 × 1010 copies g−1 soil DW) in the combined BC+ RS + CF treated soil and the RS treated soil were found to increase relative to the treatments without RS. The increase was due to the easily decomposable RS and the volatile matter (VM) constituent of the BC. Nevertheless, the resultant CO2 production was relatively similar amongst the BC, RS, and BC + RS treated soils, which was indicative of several processes, e.g., the CO2 production and reduction that occurred simultaneously but in different directions. Moreover, the highest yield of rice grains was obtained from a combined BC + RS + CF treated soil and it was 53.47 g pot−1 (8.48 t ha−1). Over time, the addition of BC to RS soil enhanced the archaeal and bacterial abundance, thereby improving yields and reducing CH4 emissions.

Effect of low temperature plasma on the functional properties of basmati rice flour

The present study deals with the application of low temperature plasma on basmati rice flour and its effect on functional properties such as gel hydrations properties, flour hydration properties, gelatinization temperatures and antioxidant properties. The water holding capacity and water binding capacity were observed to be increased with increase in plasma power and time of treatment as the air plasma is known to make the surface more hydrophilic. XRD analysis revealed there is no significance difference in the crystalline structure after the plasma treatment. DSC shows a decrease in peak temperatures (Tp) after the treatment. Hot paste viscosities were observed to be decease from 692 to 591 BU was corresponded to decrease in peak temperature. The total polyphenolic content and reducing power was observed to be increased. The effects of plasma treatment on functional groups of polyphenols were observed by changes in absorption intensities using FTIR. This study demonstrates that the low temperature plasma treatmentis capable of improving the functional properties of basmati rice.

Cr(vi) adsorption from aqueous solution by an agricultural waste based carbon

The study examined the adsorption of hexavalent chromium [Cr(vi)] from aqueous solution by acidically prepared rice husk carbon (APRHC).