Valorization of Rice Husk and Straw Agriculture Wastes of Eastern Saudi Arabia: Production of Bio-Based Silica, Lignocellulose, and Activated Carbon.

Bio-based silica, lignocellulose, and activated carbon were simply produced via the recycling of Hassawi rice biomass waste of Al-Ahsa governorate in the eastern Saudi Arabia region using a fast chemical treatment procedure. Rice husk and rice straw wastes were collected, ground, and chemically treated with sodium hydroxide to extract silica/silicate from the dried plant tissues. The liquid extract is then treated with acid solutions in order to precipitate silica/silicate at neutral medium. Lowering the pH of the supernatant to 2 resulted in the precipitation of lignocellulose. Thermal treatment of the biomass residue under N2 gas stream resulted in activated carbon production. Separated products were dried/treated and characterized using several physical examination techniques, such as FT-IR, SEM/EDX, XRD, and Raman spectroscopy in order to study their structure and morphology. Silica and lignocelluloses products were then preliminarily used in the treatment of wastewaters and water-desalination processes.

Cytotoxic Potential of Bio-Silica Conjugate with Different Sizes of Silver Nanoparticles for Cancer Cell Death.

Well-defined silver nanoparticles were doped into bio-based amorphous silica (Ag-b-SiO2) with different silver contents (from 2 to 20 wt%) by a solvent-free procedure. The four as-synthetized samples were hydrogenated at 300 °C to ensure the formation of zero-valent Ag nanoparticles. The prepared samples were characterized by X-ray powder diffraction (XRD), elemental analysis, N2 sorption measurements, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HR-TEM). The characterization data confirmed the formation of well-defined zero-valent silver nanoparticles in the range of 3-10 nm in the low-loading samples, while in high-loading samples, bulky particles of silver in the range of 200-500 nm were formed. The in vitro cytotoxic activities of the Ag-b-SiO2 samples were tested against the tumor cell lines of breast (MCF-7), liver (HepG2), and colon (HCT 116) over a concentration range of 0.01 to 1000 g. The prepared samples exhibited a wide range of cytotoxic activities against cancer cells. An inverse relationship was observed between the silver nanoparticles' size and the cytotoxic activity, while a direct relationship between the silver nanoparticles' size and the apoptotic cell death was noticed.

Evaluation of the potential of sewage sludge as a valuable fertilizer for wheat (Triticum aestivum L.) crops.

A greenhouse experiment was performed to assess the soil heavy metal pools, growth, yield, and heavy metal uptake of wheat plants (Triticum aestivum L.) that are grown at different rates in soils supplemented with sewage sludge (SS). The experimental design was completely randomized, with six replicates per treatment. The application of SS significantly increased the soil organic matter content. Generally, most growth parameters, as well as the biomass of treated wheat, were significantly increased with the amendment of SS, up to the addition rate of 40 g kg-1. The content of all heavy metals (except Cr in grains and Pb in spikes) significantly increased in different tissues of treated wheat with the increasing rate of SS application. However, all heavy metal concentrations (except for Al, Cr, Fe, and Mn in the roots) were normal and did not overcome the phytotoxic levels. The wheat was recognized by a bioaccumulation factor < 1.0 for most of the heavy metals. The translocation factor for all of the heavy metals was < 1.0. Therefore, the SS utilized in the present study could be used as a valuable organic fertilizer in wheat cultivation areas in Saudi Arabia and could also act as an eco-friendly method for the recycling of SS.

The effects of different sewage sludge amendment rates on the heavy metal bioaccumulation, growth and biomass of cucumbers (Cucumis sativus L.).

When sewage sludge is incorrectly applied, it may adversely impact agro-system productivity. Thus, this study addresses the reaction of Cucumis sativus L. (cucumber) to different amendment rates (0, 10, 20, 30, 40 and 50 g kg-1) of sewage sludge in a greenhouse pot experiment, in which the plant growth, heavy metal uptake and biomass were evaluated. A randomized complete block design with six treatments and six replications was used as the experimental design. The soil electrical conductivity, organic matter and Cr, Fe, Zn and Ni concentrations increased, but the soil pH decreased in response to the sewage sludge applications. As approved by the Council of European Communities, all of the heavy metal concentrations in the sewage sludge were less than the permitted limit for applying sewage sludge to land. Generally, applications of sewage sludge of up to 40 g kg-1 resulted in a considerable increase in all of the morphometric parameters and biomass of cucumbers in contrast to plants grown on the control soil. Nevertheless, the cucumber shoot height; root length; number of leaves, internodes and fruits; leaf area; absolute growth rate and biomass decreased in response to 50 g kg-1 of sewage sludge. All of the heavy metal concentrations (except the Cu, Zn and Ni in the roots, Mn in the fruits and Pb in the stems) in different cucumber tissues increased with increasing sewage sludge application rates. However, all of the heavy metal concentrations (except the Cr and Fe in the roots, Fe in the leaves and Cu in the fruits) were within the normal range and did not reach phytotoxic levels. A characteristic of these cucumbers was that all of the heavy metals had a bioaccumulation factor <1.0. All of the heavy metals (except Cd, Cu and Zn) had translocation factors that were <1.0. As a result, the sewage sludge used in this study could be considered for use as a fertilizer in cucumber production systems in Saudi Arabia and can also serve as a substitute method of sewage sludge disposal. Graphical Abstract The effects of different sewage sludge amendment rates on the heavy metal bioaccumulation, growth and biomass of cucumbers.

Effects of different sewage sludge applications on heavy metal accumulation, growth and yield of spinach (Spinacia oleracea L.).

In this study, we present the response of spinach to different amendment rates of sewage sludge (0, 10, 20, 30, 40 and 50 g kg-1) in a greenhouse pot experiment, where plant growth, biomass and heavy metal uptake were measured. The results showed that sewage sludge application increased soil electric conductivity (EC), organic matter, chromium and zinc concentrations and decreased soil pH. All heavy metal concentrations of the sewage sludge were below the permissible limits for land application of sewage sludge recommended by the Council of the European Communities. Biomass and all growth parameters (except the shoot/root ratio) of spinach showed a positive response to sewage sludge applications up to 40 g kg-1 compared to the control soil. Increasing the sewage sludge amendment rate caused an increase in all heavy metal concentrations (except lead) in spinach root and shoot. However, all heavy metal concentrations (except chromium and iron) were in the normal range and did not reach the phytotoxic levels. The spinach was characterized by a bioaccumulation factor <1.0 for all heavy metals. The translocation factor (TF) varied among the heavy metals as well as among the sewage sludge amendment rates. Spinach translocation mechanisms clearly restricted heavy metal transport to the edible parts (shoot) because the TFs for all heavy metals (except zinc) were <1.0. In conclusion, sewage sludge used in the present study can be considered for use as a fertilizer in spinach production systems in Saudi Arabia, and the results can serve as a management method for sewage sludge.

Levels of zinc, copper, cadmium, and lead in fruits and vegetables grown and consumed in Aseer Region, Saudi Arabia.

The levels of four metals (Zn, Cu, Cd, and Pb) were evaluated in two fruit types (apricot and fig), a fruity vegetable (tomato), and three leafy vegetables (arugula, spinach, and lettuce) that are commonly grown and consumed in Aseer Region, Saudi Arabia. Flame atomic absorption spectrophotometry was employed for quantification. The quality of results was checked by a certified reference material (NIST SRM 1570a). Good recovery values in the range of 87-104% were achieved. Metals were quantified in washed and unwashed samples to evaluate the effect of washing. Statistically, no significant difference was noticed (p>0.05), except for Zn in arugula and Cu in apricot and spinach. The levels of metals found in the analyzed fruits and vegetables were in their normal ranges in crops and not posing any serious risks to the consumers in Aseer Region. The toxic elements Pb and Cd were well below the maximum levels set in the Saudi and international food standards. Zn and Cu levels were comparable to the ranges reported in worldwide previous studies.

Combining multivariate analysis and human risk indices for assessing heavy metal contents in muscle tissues of commercially fish from Southern Red Sea, Saudi Arabia.

Jizan fishers are the major fish source for more than 1.5 million populations in the southern region in Saudi Arabia. Despite the overgrowing of various man-made activities in Jizan City, no recent study on environmental monitoring was reported. In the current study, heavy metals were quantified in muscle tissues of 12 fish species, as the most edible, from Jizan fisheries. Electrothermal atomic absorption spectrophotometry was used for quantification after microwave wet digestion. Acceptable recovery values (83.46-97.48%) for spiked fish samples with standard solutions were obtained. The following wide ranges of heavy metal concentrations (µg/g, wet weight) in studied fish species were recorded: V (0.004-0.561), Cr (0.013-0.477), Mn (0.073-0.128), As (0.002-0.935), Se (0.083-3.058), Sn (2.835-5.540), and Pb (0.150-0.386). Comparing with international permissible limits, lower levels were recorded in the current study. For total metal accumulation, the relationship between species was examined by cluster analysis, which showed that Epinephelinae was the farthest species from others. The principal component analysis shows one component indicating normal distribution of heavy metals in fish species. Different metal pollution indices (1.35-0.30), which shows the distribution of the total heavy metal concentrations in each species, were recorded. The hazard indices for muscle consumption were less than 1.0 for all studied metals at both ingestion rates except Sn which showed a marginal value of 28.9.

Modification of AOAC method 973.31 for determination of nitrite in cured meats.

A modification of AOAC Method 973.31 is proposed to improve the extraction efficiency of nitrite from cured meat samples and its subsequent quantification based on the diazotization-coupling reaction of sulfanilamide with N-(1-naphthyl)ethylenediamine dihydrochloride (NED). The various experimental parameters were thoroughly investigated. A 5 g meat sample was mixed with 400 mL water; the pH of the mixture was adjusted to 5.5 +/- 0.3 and allowed to stand for 2 h on a water bath at 80 degrees C, with occasional shaking for the complete extraction of nitrite. After quantitative filtration, an aliquot was mixed with chloroacetic-chloroacetate buffer, pH 1.80 +/- 0.05, sulfanilamide, and NED, and the absorbance of the resulting azodye was recorded at 540 nm against water as a reference. Following the recommended procedure, a linear calibration graph was obtained for up to 0.8 microg/mL NO2(-), with a correlation coefficient of 0.9996 and a detection limit (based on the 3 Sb-criterion) of 5.6 ng/mL NO2(-). The proposed method was conveniently applied to various cured meat samples and was validated by comparison with the original AOAC method and by recovery experiments that gave quantitative results (94-98%) with convenient reproducibility. Statistical analysis of the analytical data could not detect any systematic error and revealed the high accuracy and precision of the proposed method.

Highly sensitive and selective catalytic determination of formaldehyde and acetaldehyde.

A highly sensitive, simple and selective kinetic method was developed for the determination of ultra-trace levels of formaldehyde and acetaldehyde based on their catalytic effect on the oxidation of N,N-diethyl-p-phenylenediamine (DPD) with hydrogen peroxide. The reaction was monitored spectrophotometrically by tracing the formation of the red-colored oxidized product of DPD at 510nm, within 30s of mixing the reagents. The optimum reaction conditions were: 20mmolL(-1) DPD, 250mmolL(-1) H(2)O(2), 150mmolL(-1) phosphate, 150mmolL(-1) citrate and pH 6.60+/-0.05 at 25 degrees C. Following the recommended procedure, formaldehyde and acetaldehyde could be determined with linear calibration graphs up to 0.50 and 1.4microg mL(-1) and detection limits, based on the 3S(b)-criterion, of 0.015 and 0.035microg mL(-1), respectively. In addition, analytical data for other 10 aldehydes were also presented. The high sensitivity and selectivity of the proposed method allowed its successful application to rain water, mainstream smoke (MSS) and disposed tips of smoked cigarettes (DTSC). A sample aliquot was directly analyzed for its total water-soluble aldehyde content. A second sample aliquot was heated at 80 degrees C for 10min to expel acetaldehyde and the aliquot was analyzed for its content of other water-soluble aldehydes (expressed as formaldehyde equivalent), and acetaldehyde was determined by difference. The analytical results were in excellent agreements with those obtained following the standard HPLC method based on pre-column derivatization with 2,4-dinitrophenylhydrazine. Moreover, published catalytic-spectrophotometric methods for the determination of aldehydes were reviewed.

Highly sensitive catalytic determination of molybdenum.

A novel, highly sensitive, selective, and simple kinetic method was developed for the determination of Mo(VI) based on its catalytic effect on the oxidation of 1-amino-2-naphthol-4-sulfonic acid (ANSA) with H(2)O(2). The reaction was followed spectrophotometrically by tracing the oxidized product at 465nm after 30min of mixing the reagents. The optimum reaction conditions were: 10mmol l(-1) ANSA, 50mmol l(-1) H(2)O(2), 100mmol l(-1) acetate buffer of pH 5.0+/-0.05 and at 40 degrees C. Addition of 200microg ml(-1) diethylenetriaminepentaacetic acid (DTPA) conferred high selectivity for the proposed method. Following the recommended procedure, Mo(VI) could be determined with a linear calibration graph up to 2.5ng ml(-1) and a detection limit, based on the 3S(b)-criterion, of 0.027ng ml(-1). The unique sensitivity and selectivity of the implemented method allowed its direct application to the determination of Mo(VI) in natural and industrial waste water. The method was validated by comparison with the standard ETAAS method. Moreover, published catalytic-spectrophotometric methods for the determination of molybdenum were reviewed.

A novel kinetic determination of dissolved chromium species in natural and industrial waste water.

A highly sensitive, selective and simple kinetic method was developed for the determination of dissolved chromium species based on the catalytic effect of Cr(III) and/or Cr(VI) on the oxidation of 2-amino-5-methylphenol (AMP) with H(2)O(2). The fixed time and initial rate variants were used for kinetic spectrophotometric measurements by tracing the oxidized product at 400nm for 10min after starting the reaction. Boric acid and Tween-40 exerted pronounced activating and micellar sensitizing effects on the studied redox reaction, respectively. The optimum reaction conditions were: 3.0mmoll(-1) AMP, 0.45moll(-1) H(2)O(2), 0.50moll(-1) boric acid, 4v/v% Tween-40, 10mmoll(-1) phosphate buffer and pH 6.45+/-0.02 at 35 degrees C. Both Cr(III) and Cr(VI) ions exerted the same catalytic effect on the studied reaction. Linear calibration graphs were obtained for the determination of up to 6.0ngml(-1) Cr with detection limits of 0.054 and 0.10ngml(-1) Cr; following the fixed time and initial rate methods, respectively. The proposed method was successfully applied to the speciation and determination of trace levels of dissolved Cr(III) and Cr(VI) in natural and effluents of industrial waste water. The total dissolved Cr(III) and Cr(VI) species was determined first. In a second run, Cr(VI) was determined alone after precipitation of Cr(III) ions in presence of Al(OH)(3) collector, where Cr(III) is then determined by difference. Moreover, published catalytic-spectrophotometric methods for chromium determination were reviewed.