Sorption–Desorption Behavior of Doxycycline in Soil–Manure Systems Amended with Mesquite Wood Waste Biochar

Elevated levels of doxycycline (DC) have been detected in the environment due to its extensive utilization as a veterinary antibiotic. Sorption–desorption behavior of DC in soil affects its transport, transformation, and availability in the environment. Thus, sorption–desorption behavior of DC was explored in three soils (S1, S2, and S3) after manure application with and without mesquite wood-waste-derived biochar (BC) pyrolyzed at 600 °C. Sorption batch trials demonstrated the highest DC sorption in soil S1 as compared to S2 and S3, either alone or in combination with manure or manure + BC. Chemical sorption and pore diffusion were involved in DC sorption, as indicated by the kinetic models. Soil S1 with manure + BC exhibited the highest Langmuir model predicted sorption capacity (18.930 mg g−1) compared with the other two soils. DC sorption capacity of soils was increased by 5.0–6.5-fold with the addition of manure, and 10–13-fold with BC application in a soil–manure system. In desorption trials, manure application resulted in 67%, 40%, and 41% increment in DC desorption in soil S1, S2, and S3, respectively, compared to the respective soils without manure application. In contrast, BC application reduced DC desorption by 73%, 66%, and 65%, in S1, S2, and S3, respectively, compared to the soils without any amendment. The highest DC sorption after BC application could be due to H bonding, π–π EDA interactions, and diffusion into the pores of BC. Hence, mesquite wood-waste-derived BC can effectively be used to enhance DC retention in contaminated soil to ensure a sustainable ecosystem

Influence of Acidified Biochar on CO2–C Efflux and Micronutrient Availability in an Alkaline Sandy Soil

Biochar, an alkaline carbonaceous substance resulting from the thermal pyrolysis of biomass, reportedly enhances the micronutrient availability in acidic soils with little or no effect on alkaline soils. In this study, biochars were produced from poultry manure (PM) at 350 °C and 550 °C (BC350 and BC550 respectively). The acidified biochars (ABC350 and ABC550, respectively) were incorporated into an alkaline sandy soil, and their effects on the soil micronutrients (Cu, Fe, Mn and Zn) availability, and CO2–C efflux were investigated in a 30-day incubation study. The treatments (PM, BC350, BC550, ABC350, and ABC550) were administered in triplicate to 100 g soil at 0%, 1%, and 3% (w/w). Relative to the poultry manure treatment, acidification drastically reduced the pH of BC350 and BC550 by 3.13 and 4.28 units, respectively, and increased the micronutrient availability of the studied soil. Furthermore, the biochars (both non-acidified and acidified) reduced the CO2 emission compared to that of the poultry manure treatment. After 1% treatment with BC550 and ABC550, the CO2 emissions from the soil were 89.6% and 91.4% lower, respectively, than in the 1% poultry manure treatment. In summary, acidified biochar improved the micronutrient availability in alkaline soil, and when produced at higher temperature, can mitigate the CO2 emissions of soil carbon sequestration

Mitigating the Toxic Effects of Chromium on Wheat (Triticum aestivum L.) Seed Germination and Seedling Growth by Using Biochar and Polymer-Modified Biochar in Contaminated Soil

The present study was conducted to investigate the potential influences of biochar in mitigating the phytotoxic effects of hexavalent chromium (CrVI) on the germination of wheat (Triticum aestivum L.). Biochar (JBC) was produced from Jujube (Ziziphus jujube L.) wood waste at three different pyrolysis temperatures (300 °C, 500 °C and 700 °C), which was later polymerized (JPBC) via the solution-polymerization method. Phytotoxicity of CrVI was induced to wheat seeds at variable CrVI application rates (5, 10, 20, 40 mg L−1). Applied CrVI concentrations confined the seed germination and seedling growth in order of: 5 < 10 < 20 < 40 mg L−1. The application of JBCs (0.2 g per petri plate) resulted in a 150% increase in shoot length, while dry biomass was increased by 250% with JPBCs application. Uptake of CrVI was significantly lower in JBC-300 (7.74 μg/seedling) and JPBC-300 (1.13 μg/seedling) treatments, as compared to control (13.24 μg/seedling), at the highest stress level (40 mg L−1). Therefore, the findings of the current study showed that JBCs and JPBCs performed excellently in improving seedling growth while JPBCs performed more efficiently than pristine JBCs in mitigating CrVI phytotoxicity and availability

Mitigating the Toxic Effects of Chromium on Wheat (<i>Triticum aestivum</i> L.) Seed Germination and Seedling Growth by Using Biochar and Polymer-Modified Biochar in Contaminated Soil

The present study was conducted to investigate the potential influences of biochar in mitigating the phytotoxic effects of hexavalent chromium (CrVI) on the germination of wheat (Triticum aestivum L.). Biochar (JBC) was produced from Jujube (Ziziphus jujube L.) wood waste at three different pyrolysis temperatures (300 °C, 500 °C and 700 °C), which was later polymerized (JPBC) via the solution-polymerization method. Phytotoxicity of CrVI was induced to wheat seeds at variable CrVI application rates (5, 10, 20, 40 mg L−1). Applied CrVI concentrations confined the seed germination and seedling growth in order of: 5 −1. The application of JBCs (0.2 g per petri plate) resulted in a 150% increase in shoot length, while dry biomass was increased by 250% with JPBCs application. Uptake of CrVI was significantly lower in JBC-300 (7.74 μg/seedling) and JPBC-300 (1.13 μg/seedling) treatments, as compared to control (13.24 μg/seedling), at the highest stress level (40 mg L−1). Therefore, the findings of the current study showed that JBCs and JPBCs performed excellently in improving seedling growth while JPBCs performed more efficiently than pristine JBCs in mitigating CrVI phytotoxicity and availability

Variations in composition and stability of biochars derived from different feedstock types at varying pyrolysis temperature

Feedstock type and pyrolysis temperature primarily affect the properties of resultant biochar. Therefore, the effects of several different feedstock types and various pyrolysis temperatures on structural, chemical, proximate, morphological, and elemental compositional characteristics of the resultant biochars were explored. Nine types of wastes (date palm fiber waste (DF), date palm leaf waste (DL), date palm petiole waste (DP), tomato plant waste (TM), cucumber plant waste (CC), poultry litter (PL), chicken feather waste (CH), cow dung (CD), and conocarpus waste (CN) were collected and pyrolyzed at varying temperatures (300, 400, 500, and 600 °C) to produce different types of biochar, which were subjected to physio-chemical, proximate, and ultimate analyses. Distinctive variations were observed in the characteristics of the used feedstock types and their derived biochars. The biochars derived from CC exhibited the highest pH (8.41–11.02), while the biochars derived from CH demonstrated the minimum pH (7.99–8.40). Overall, the biochars derived from PL, CC, TM, and DL showed higher contents of C as compared to the other biochars, suggesting higher stability. Contrarily, the biochars derived from CH and CD exhibited a higher labile C fraction, indicating its lower recalcitrance than other tested biochars. The biochars produced at low pyrolysis temperatures showed a comparatively amorphous surface with lower alkalinity and electrical conductivity, while higher moisture, net negative charge, labile carbon, and volatile contents. Contrarily, the higher pyrolysis temperature demonstrated the higher ash and fixed carbon contents with more surface porosity and comparatively higher non-labile carbon fraction. Biochar produced at 600 °C exhibited H/C and O/C atomic ratios of <0.2, suggesting higher stability and recalcitrant potential against biochars produced below 500 °C, which showed H/C and O/C atomic ratios in the range of 0.2–0.4

Soil Phosphorus Fractionation and Bio-Availability in a Calcareous Soil as Affected by Conocarpus Waste Biochar and Its Acidified Derivative

Biochar possesses more profound effects on the availability of soil P in acidic soil than in alkaline and/or calcareous soil, mainly due to P fixation. Therefore, biochar derived from Conocarpus waste (BC) was acidified with sulfuric acid to produce acidified biochar (ABC) and incorporated into a calcareous soil planted with alfalfa in order to investigate P availability and fractionation. Additionally, the changes in some other soil chemical properties were investigated. Both BC and ABC were applied at three rates (0%, 2.5%, and 5%) along with P fertilizer application at four rates (0, 75, 150 and 300 ppm). The results showed that acidification remarkably reduced the pH of ABC by 6.84 units. The application of ABC considerably lowered the soil pH; however, it did not significantly increase P availability in the studied soil. Furthermore, BC, especially at a higher application rate, increased the extractable soil K. Similarly, the amendments increased the soil cation exchangeable capacity (CEC) and soil organic matter (OM), where a profound increase was observed at a higher application rate in the case of soil OM. Similarly, soil-available micronutrients were increased over the control, where a more profound increase was observed in soils treated with ABC. The NaHCO3&minus;P (exchangeable) fraction increased with increasing fertilizer application rate while the residual&ndash;P decreased. Therefore, BC and ABC could be used to improve soil quality and enhance soil nutrient availability. However, further studies are required on how to significantly improve soil available P in calcareous soil

Soil Phosphorus Fractionation and Bio-Availability in a Calcareous Soil as Affected by <i>Conocarpus</i> Waste Biochar and Its Acidified Derivative

Biochar possesses more profound effects on the availability of soil P in acidic soil than in alkaline and/or calcareous soil, mainly due to P fixation. Therefore, biochar derived from Conocarpus waste (BC) was acidified with sulfuric acid to produce acidified biochar (ABC) and incorporated into a calcareous soil planted with alfalfa in order to investigate P availability and fractionation. Additionally, the changes in some other soil chemical properties were investigated. Both BC and ABC were applied at three rates (0%, 2.5%, and 5%) along with P fertilizer application at four rates (0, 75, 150 and 300 ppm). The results showed that acidification remarkably reduced the pH of ABC by 6.84 units. The application of ABC considerably lowered the soil pH; however, it did not significantly increase P availability in the studied soil. Furthermore, BC, especially at a higher application rate, increased the extractable soil K. Similarly, the amendments increased the soil cation exchangeable capacity (CEC) and soil organic matter (OM), where a profound increase was observed at a higher application rate in the case of soil OM. Similarly, soil-available micronutrients were increased over the control, where a more profound increase was observed in soils treated with ABC. The NaHCO3−P (exchangeable) fraction increased with increasing fertilizer application rate while the residual–P decreased. Therefore, BC and ABC could be used to improve soil quality and enhance soil nutrient availability. However, further studies are required on how to significantly improve soil available P in calcareous soil

The Potential Use of Zeolite, Montmorillonite, and Biochar for the Removal of Radium-226 from Aqueous Solutions and Contaminated Groundwater

The present work investigated the potential of using zeolite (clinoptilolite), montmorillonite (Swy2), and Conocarpus biochar as adsorbents to remove 226Ra from aqueous solution. The effect of the initial 226Ra concentrations on sorbents&rsquo; equilibrium activity concentrations and sorbents&rsquo; radium removal efficiency were investigated. The results showed that zeolite has a higher removal efficiency for 226Ra in comparison with the efficiencies of montmorillonite and biochar. In addition to the linear isotherm model, the Freundlich model, followed by Temkin&rsquo;s model, provided a better description of the adsorption process than the Langmuir model. Kinetic studies indicated that a pseudo-second-order kinetic model could be the best fit for the adsorption of 226Ra onto the three investigated sorbents, which suggests that the mechanism of adsorption of 226Ra by sorbents was chemisorption. The intraparticle diffusion model indicated that adsorption of 226Ra onto the sorbents involves a multistep process: (i) boundary layer diffusion and (ii) intraparticle diffusion. Moreover, the remediation of groundwater samples polluted with 226Ra was assessed using the investigated sorbents; the results showed that zeolite also has the highest removal efficiency among other sorbents. Thus, the low cost, availability, and the high adsorption efficiency of zeolite can be a promising sorbent on 226Ra removal from aqueous solutions and groundwater remediation

Evaluation of Groundwater for Arsenic Contamination Using Hydrogeochemical Properties and Multivariate Statistical Methods in Saudi Arabia

The aim of this research is to evaluate arsenic distribution and associated hydrogeochemical parameters in 27 randomly selected boreholes representing aquifers in the Al-Kharj geothermal fields of Saudi Arabia. Arsenic was detected at all sites, with 92.5% of boreholes yielding concentrations above the WHO permissible limit of 10 μg/L. The maximum concentration recorded was 122 μg/L (SD = 29 μg/L skewness = 1.87). The groundwater types were mainly Ca+2-Mg+2-SO4-2-Cl− and Na+-Cl−-SO4-2, accounting for 67% of the total composition. Principal component analysis (PCA) showed that the main source of arsenic release was geothermal in nature and was linked to processes similar to those involved in the release of boron. The PCA yielded five components, which accounted for 44.1%, 17.0%, 10.1%, 08.4%, and 06.5% of the total variance. The first component had positive loadings for arsenic and boron along with other hydrogeochemical parameters, indicating the primary sources of As mobilization are derived from regional geothermal systems and weathering of minerals. The remaining principal components indicated reductive dissolution of iron oxyhydroxides as a possible mechanism. Spatial evaluation of the PCA results indicated that this secondary mechanism of arsenic mobilization may be active and correlates positively with total organic carbon. The aquifers were found to be contaminated to a high degree with organic carbon ranging from 0.57 mg/L to 21.42 mg/L and showed high concentrations of NO3- ranging from 8.05 mg/L to 248.2 mg/L

Removal of Cr(VI) and Toxic Ions from Aqueous Solutions and Tannery Wastewater Using Polymer-Clay Composites

Polymer-clay composites were prepared by natural zeolite (clinoptilolite) or naturally local clay deposits in an N,N-methylene-bis-acrylamide as cross-linked. The resultant composites were used for the removal of Cr(VI) from an aqueous solution. Additionally, their effects on soluble ions of tannery wastewater were investigated. The produced composites were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The results showed that Cr(VI) removal is dependent upon initial concentrations and pH. The adsorption quantity of Cr(VI) onto the polymerized clay deposit followed by polymerized zeolite exhibited higher values than their original samples. The polymer-clay composite of clay deposit showed the highest removal of 76.3–100% overall initial concentrations of 10–50 mg L−1 and at initial pH of 2. Kinetics of Cr(VI) removal by various sorbents was predicted using a pseudo–second order model. Our findings showed that the levels of salinity and various soluble ions (Cr2+, Na+, Cl− and SO42−) in tannery wastewater are very high, and their levels were reduced after treatment, especially by polymerized sorbents. It could be concluded that the polymer-clay composites may be employed as a highly efficient sorbent for the removal of Cr(VI) and toxic ions from the wastewater