Impacts of kaolinite enrichment on biochar and hydrochar characterization, stability, toxicity, and maize germination and growth.

In this study, biochar (BC) and hydrochar (HC) composites were synthesized with natural kaolinite clay and their properties, stability, carbon (C) sequestration potential, polycyclic aromatic hydrocarbons (PAHs) toxicity, and impacts on maize germination and growth were explored. Conocarpus waste was pretreated with 0%, 10%, and 20% kaolinite and pyrolyzed to produce BCs (BC, BCK10, and BCK20, respectively), while hydrothermalized to produce HCs (HC, HCK10, and HCK20, respectively). The synthesized materials were characterized using X-ray diffraction, scanning electron microscope analyses, Fourier transform infrared, thermogravimetric analysis, surface area, proximate analyses, and chemical analysis to investigate the distinction in physiochemical and structural characteristics. The BCs showed higher C contents (85.73-92.50%) as compared to HCs (58.81-61.11%). The BCs demonstrated a higher thermal stability, aromaticity, and C sequestration potential than HCs. Kaolinite enriched-BCs showed the highest cation exchange capacity than pristine BC (34.97% higher in BCK10 and 38.04% higher in BCK20 than pristine BC), while surface area was the highest in kaolinite composited HCs (202.8% higher in HCK10 and 190.2% higher in HCK20 than pristine HC). The recalcitrance index (R50) speculated a higher recalcitrance for BC, BCK10, and BCK20 (R50 > 0.7), minimal degradability for HCK10 and HCK20 (0.5 < R50 < 0.7), and higher degradability for biomass and HC (R50 < 0.5). Overall, increasing the kaolinite enrichment percentage significantly enhanced the thermal stability and C sequestration potential of charred materials, which may be attributed to changes in the structural arrangements. The ∑ total PAHs concentration in the synthesized materials were below the USEPA's suggested limits, indicating their safe use as soil amendments. Germination indices reflected positive impacts of synthesized charred materials on maize germination and growth. Therefore, we propose that kaolinite-composited BCs and HCs could be considered as efficient and cost-effective soil amendments for improving plant growth.

Microplastic-Assisted Removal of Phosphorus and Ammonium Using Date Palm Waste Derived Biochar.

Microplastics (MPs) are emerging environmental pollutants worldwide, posing potential health risks. Moreover, MPs may act as vectors for other contaminants and affect their fate, transport, and deposition in the environment. Therefore, efficient and economical techniques are needed for the removal of contemporary MPs and contaminants from the environment. The present research study investigated the sorption of phosphorus (P) and ammonium (NH4+) onto date palm waste-derived biochar (BC) from an aqueous solution in the presence of polyamide (PA) and polyethylene (PE) MPs. The BC was prepared at 600 °C, characterized for physio-chemical properties, and applied for P and NH4+ removal via isotherm and kinetic sorption trials. The results of the sorption trials demonstrated the highest removal of NH4+ and P was obtained at neutral pH 7. The highest P sorption (93.23 mg g-1) by BC was recorded in the presence of PA, while the highest NH4+ sorption (103.76 mg g-1) was found with co-occurring PE in an aqueous solution. Sorption isotherm and kinetics models revealed that P and NH4+ removal by MP-amended BC followed chemisorption, electrostatic interaction, precipitation, diffusion, and ion exchange mechanisms. Overall, co-existing PA enhanced the removal of P and NH4+ by 66% and 7.7%, respectively, while co-existing PE increased the removal of P and NH4+ by 55% and 30%, respectively, through the tested BC. Our findings suggested that converting date palm waste into BC could be used as a competent and economical approach to removing P and NH4+ from contaminated water. Furthermore, microplastics such as PE and PA could assist in the removal of P and NH4+ from contaminated water using BC.

Scavenging microplastics and heavy metals from water using jujube waste-derived biochar in fixed-bed column trials.

Extensive production and utilization of plastic products have resulted in the generation of microplastics (MPs), subsequently polluting the environment. The efficiency of biochars (BCs) derived from jujube (Ziziphus jujube L.) biomass (300 °C and 700 °C) for nylon (NYL) and polyethylene (PE) removal from contaminated water was explored in fixed-bed column trials. The optimum pH for the removal of both MPs was found 7. Both of the produced biochars demonstrated >99% removal of the MPs, while the sand filter exhibited a maximum of 78% removal of MPs. BC produced at 700 °C (BC700) showed 33-fold higher MPs retention, while BC produced at 300 °C (BC300) exhibited 20-fold higher retention, as compared to sand filters, indicating the higher efficiency of BC produced at higher pyrolysis temperature. Entrapment into the pores, entanglement with flaky structures of the BCs, and electrostatics interactions were the major mechanism for MPs retention in BCs. The efficiency of MPs-amended BCs was further explored for the removal of Pb(II) and Cd(II) in fixed-bed column trials. BC700 amended with PE and NYL exhibited the highest 50% breakthrough time (2114.23 and 2024.61 min, respectively, for Pb(II) removal and 2107.92 and 1965.19 min, respectively, for Cd(II) removal), as compared to sand filters (38.07 and 60.49 min for Pb(II) and Cd(II) removal, respectively). Thomas model predicted highest adsorption capacity was exhibited by BC700 amended with PE (584.34 and 552.80 mg g-1, for Pb(II) and Cd(II) removal, respectively), followed by BC700 amended with NYL (557.65 and 210.59 mg g-1 for Pb(II) and Cd(II) removal, respectively). Therefore, jujube waste-derived BCs could be used as efficient adsorbents to remove PE and NYL from contaminated water, while MPs-loaded BCs can further be utilized for higher adsorption of Pb(II) and Cd(II) from contaminated aqueous media. These findings suggest that BC could be used as an efficient adsorbent to remove the co-existing MPs-metals ions from the environment on a sustainable basis.

Date palm-magnetized biochar for in-situ stabilization of toxic metals in mining-polluted soil: evaluation using single-step extraction methods and phytoavailability.

Mining activities provide a pathway for the entry and accumulation of various heavy metals in soil, which ultimately leads to severe environmental pollution. Utilization of various immobilizing agents could restore such contaminated soils. Therefore, in this study, date palm-derived biochars (BCs: produced at 300 °C, 500 °C and 700 °C) and magnetized biochars (MBCs) were employed to stabilize heavy metals (Cd, Pb, Cu and Zn) in mining polluted soil. Metal polluted soil was amended with BCs and MBCs at w/w ratio of 2% and cultivated with wheat (Triticum aestivum L.) in a greenhouse. After harvesting, dry and fresh biomass of plants were recorded. The soil and plant samples were collected, and the concentrations of heavy metals were measured after extracting with water, DTPA (diethylenetriaminepentaacetic acid), EDTA (ethylenediaminetetraacetic acid), and acetic acid. BCs and MBCs resulted in reduced metal availability and uptake, with higher fresh and dry biomass (>36%). MBCs showed maximum decrease (>70%) in uptake and shoot concentration of metals, as these reductions for Cd and Pb reached below the detection limits. Among all single-step extractions, the DTPA-extractable metals showed a significant positive correlation with shoot concentrations of tested metals. Thus, the synthesized BCs and MBCs could effectively be used for stabilizing heavy metals and improve plant productivity in multi-contaminated soils. However, future studies should focus on long term field trials to restore contaminated mining soils using modified biochars.

This study has demonstrated the performance of magnetized biochars for in-situ stabilization of toxic metals (Cd, Pb, Cu and Zn) in mining polluted soil by single extraction method. All the produced BCs and magnetized BCs showed great potential in immobilizing the metals and reducing their availability in soil, consequently decreasing their shoot concentration and plant uptake. Significant negative correlations were observed between soil pH and metal extraction from applied extraction methods such as water soluble, DTPA, and EDTA extractions. We found DTPA as a suitable extractant for investigating metal uptake in plant in multi-contaminated soils. Treatments with MBCs showed maximum decrease in plant uptake and concentration of studied metals. Thus, application of MBCs could efficiently immobilize soil heavy metals.

Immobilization and mitigation of chromium toxicity in aqueous solutions and tannery waste-contaminated soil using biochar and polymer-modified biochar.

This study was conducted to investigate the potential of Jujube (Ziziphus jujube L) wood waste-derived biochar (BC) and its derivative polymer-modified biochar (PBC) in removing hexavalent chromium (CrVI) from aqueous solutions and in achieving Cr stabilization in tannery waste-contaminated soil. BC was produced at three different pyrolysis temperature (300 °C, 500 °C, 700 °C) and was polymerized with acrylamide and N, N1 methylenebisacrylamide. The results showed that CrVI adsorption is a function of the pH and CrVI initial concentration of the solution. The PBC showed highest sorption efficiency for CrVI removal, which amounted to 76.4%-99.6% of the CrVI overall initial concentrations (5-40 mg L-1) at an initial pH of 2. In greenhouse, wheat (Triticum aestivum L) was cultivated as a test crop in pots with tannery waste-contaminated soil along with BCs and PBCs amendments. The BC and PBC amended soil showed 47.7% and 65% less Cr uptake by the plant roots in comparison with unamended soil, respectively. In addition, zero concentration of Cr in the plant shoots was noted with the PBC-amended soil, while the Cr concentration in the shoots was decreased by 89% with the BC-amended soil. Thus, it was concluded that BC and PBC have great potential in removing CrVI from aqueous phases and in decreasing the Cr mobility and bioavailability in soil.

Pyrolytic and hydrothermal carbonization of date palm leaflets: Characteristics and ecotoxicological effects on seed germination of lettuce.

Biochar has vital importance as soil additives due to its characteristics, which are responsible for alleviating environmental problems and climate change. These additives should be evaluated to understand their physico-chemical properties and their ecotoxicological effects on plant growth. Therefore, this study aimed to (i) distinguish the properties of biochar produced from date palm and its derivative hydrochar, and (ii) investigate their ecotoxicological effects. Specifically, the biochar and hydrochar were produced from date palm leaflets by pyrolysis and hydrothermal carbonization, respectively. The produced chars were evaluated for their characteristics before and after water washing, and for their ecotoxicological effects on seed germination of lettuce (Lactuca sativa L). The results show that water washing lowered biochar's pH and increased hydrochar's pH. Moreover, water washing of hydrochar caused a significant reduction in the total content of essential elements such as Ca, Mg, Mn, and Zn. Lettuce germination was significantly inhibited to 20% by hydrochar, whereas biochar enhanced lettuce growth by increasing shoot length (by 51%) and dry biomass (by 114%). Hydrochar toxicity was correlated (R > 0.95 at p = 0.05) with high contents of total polyaromatic hydrocarbons (98.8 mg kg-1). Pre-treatment and assessment of hydrochar should be taken into account prior to application as a soil amendment.

Engineered biochar composites with zeolite, silica, and nano-zerovalent iron for the efficient scavenging of chlortetracycline from aqueous solutions.

Date palm waste-derived biochar (DBC) was produced through pyrolysis (600 °C) and modified with zeolite (Z-DBC), silica (S-DBC), or nano-zerovalent iron (nZVI-DBC) to design efficient sorbents. The pristine and engineered biochars were characterized by SEM, XRD, BET, TGA, CHNS-O, and FTIR to investigate the surface, structural, and mineralogical composition. The nZVI-DBC exhibited lowest pH (6.15) and highest surface area (220.92 m2 g-1), carbon (80.55%), nitrogen (3.78%), and hydrogen (11.09%) contents compared with other biochars. Isotherm sorption data for chlortetracycline (CTC) removal from aqueous solutions was described well by Langmuir and Redlich-Peterson isotherms showing the highest fitness (R2 values in the range of 0.88-0.98 and 0.88-0.99, respectively). Langmuir predicted maximum CTC adsorption capacity was in order of nZVI-DBC (89.05 mg g-1) > S-DBC (45.57 mg g-1) > Z-DBC (30.42 mg g-1) > DBC (28.19 mg g-1). Kinetics adsorption data was best described by power function model (R2 = 0.93-0.99), followed by interaparticle diffusion (R2 = 0.85-0.96) model. The nZVI-DBC performed outclass by removing 98% of CTC, followed by S-DBC (68%), Z-DBC (35%), and DBC (36%). Chemisorption, H-bonding, and interaparticle diffusion were the operating mechanisms for CTC adsorption onto DBC, S-DBC, and Z-DBC, while π-π electron donor-accepter interactions and redox reactions augmented these mechanisms for highest CTC adsorption onto nZVI-DBC. Therefore, nZVI-DBC may serve as an efficient green technology for the removal of CTC from aqueous solutions and to reduce surface date palm waste pollution. Graphical abstract .