Search Results (9)

Acidic agricultural soils are frequently challenged by co-occurring heavy metal contamination and greenhouse gas (GHG) emissions. While biochar is widely used for integrated remediation, the specific role of silicon (Si) in modulating its effectiveness in cadmium (Cd) stabilization and nitrous oxide (N₂O) mitigation remains insufficiently understood. This study evaluated the co-remediation efficacy of two types of high-Si (bamboo leaves, ML; rice straw, RS) and two types of low-Si (Camellia oleifera leaves, CL; Camellia oleifera shells, CS) biochar, produced at 450 °C, within a Cd-contaminated and nitrogen-fertilized acidic soil. Results from a 90-day incubation showed that while all biochar effectively immobilized Cd, the low-Si CL biochar exhibited a superior stabilization efficiency of 66.2%. This enhanced performance was attributed to its higher soil organic carbon (SOC) and moderate dissolved organic carbon (DOC) release, which facilitated robust Cd²⁺ sorption and complexation. In contrast, high-Si biochar was more effective in mitigating cumulative N₂O emissions (up to 67.8%). This mitigation was strongly associated with an elevated abundance of the nosZ gene (up to 48.1%), which catalyzes the terminal step of denitrification. Soil pH and DOC were identified as pivotal drivers regulating both Cd bioavailability and N₂O dynamics. Collectively, low-Si biochar is preferable for Cd stabilization in acidic soils, whereas high-Si biochar is more effective at elevating pH and reducing N₂O emissions. These findings emphasize that optimizing co-remediation outcomes necessitates a targeted approach, selecting biochar based on the specific contamination profile and desired environmental benefits. Full article

Agricultural soil is the main source of greenhouse gas emissions, among which carbon dioxide (CO₂) is an important greenhouse gas, impacting the global climate. In China, as a large rice-producing country, carbon sequestration and CO₂ mitigation in paddy soil are crucial for the mitigation of global climate change. While biochar has been widely used in the mitigation of soil greenhouse gas emissions, the application site of biochar, i.e., whether or not it is the same as its feedstocks, may generate different effects on soil CO₂ emissions due to the differences in the element and nutrient concentrations in its feedstocks, especially when applied in fertilized soil. In order to explore the effects of biochar application with different feedstocks on the mitigation of CO₂ emissions from paddy soil, this experiment took paddy soil in a red soil area as the research object, using rice straw and Camellia oleifera fruit shell as raw materials to produce biochar (adding an amount of 40 g kg⁻¹ soil) and urea as an external nitrogen source (adding an amount of 200 mg kg⁻¹ soil). The effects of two different types of biochar derived from feedstocks with different producing origins on the CO₂ emissions from paddy soil were studied via laboratory control incubation studies. The results showed that (1) the effects of rice straw biochar addition on the soil pH, NO₃⁻-N and total available nitrogen (AN) content were significantly higher than those of Camellia oleifera fruit shell biochar (the scale of the increase was higher by 6.40%, 579.7% and 180.1%, respectively). (2) The CO₂ emission rate and cumulative emissions of soil supplemented with rice straw biochar were significantly lower than in that supplemented with Camellia oleifera fruit shell biochar (decreases of 28.0% and 27.5%, respectively). Our findings suggest that the efficiency of emission mitigation of rice straw biochar is better than that of Camellia oleifera fruit shell applied to paddy soil. While future studies considering more types of greenhouse gases will be necessary to expand these findings, this study indicates that biochar prepared from in situ feedstock can be used to reduce greenhouse gas emissions in rice fields, so as to ensure sustainable development and achieve energy conservation and emission reduction goals. This study will benefit future agricultural practices when choosing biochar as a greenhouse gas mitigation strategy in the context of global warming, as well as other global changes following global warming, caused by elevated atmospheric greenhouse gases. Full article

This study prepared sulfonated Camellia oleifera shell biochar using Camellia oleifera shell agricultural waste as a carbon source, and evaluated its performance as a catalyst for preparing biodiesel. The biochar obtained from carbonizing Camellia oleifera shells at 500 °C for 2 h serves as the carbon skeleton, and then the biochar is sulfonated with chlorosulfonic acid. The sulfonic acid groups are mainly grafted onto the surface of Camellia oleifera shell biochar through covalent bonding to obtain sulfonic acid type biochar catalysts. The catalysts were characterized by Scanning Electron Microscope (SEM), X-ray diffraction (XRD), Nitrogen adsorption-desorption Brunel-Emmett-Taylor Theory (BET), and Fourier-transform infrared spectroscopy (FT-IR). The acid density of the sulfonated Camellia oleifera fruit shell biochar catalyst is 2.86 mmol/g, and the specific surface area is 2.67 m²/g, indicating high catalytic activity. The optimal reaction conditions are 4 wt% catalyst with a 6:1 alcohol to oil ratio. After esterification at 70 °C for 2 h, the yield of biodiesel was 91.4%. Under the optimal reaction conditions, after four repeated uses of the catalyst, the yield of biodiesel still reached 90%. Therefore, sulfonated Camellia oleifera shell biochar is a low-cost, green, non-homogeneous catalyst with great potential for biodiesel production by esterification reaction in future development. Full article

It is important to recover La³⁺ from metallurgical solutions or wastewater. However, the recovery rate of La³⁺ is usually less than 1% and the recovery methods are not environmentally friendly or user-friendly. Therefore, a straightforward, efficient, clean, and economically friendly method is needed. In this investigation, a modified adsorbent, COSAC-Na₂EDTA-15, which was made from the Camellia oleifera shell (COS) and disodium ethylenediaminetetraacetic acid (Na₂EDTA), was invented. In addition, characterization of the COSAC-Na₂EDTA-15 adsorbent was conducted using SEM and XPS, and the principle of adsorption was revealed. The adsorption kinetics followed P-S-O KM, while the isotherm of COS-activated carbon (COSAC) aligned more closely with the Langmuir model. Compared to COSAC, the maximum La³⁺ adsorption capacity of COSAC-Na₂EDTA-15 increased from 50 to 162.43 mg/g, and the content of O and N changed from 7.31% and 1.48% to 12.64% and 4.15%, respectively. The surface of the COSAC-Na₂EDTA-15 exhibited abundant C, N, and O elements, and La³⁺ was detected on the sample surface after adsorption. The test and analysis results fully indicate that La³⁺ can be successfully adsorbed on the surface of COSAC-Na₂EDTA-15. Because of its easy preparation, low cost, and superior performance, activated carbon made from COS finds extensive applications in the adsorption and recovery of rare earth elements. Full article

Tetracycline (TC) is a common antibiotic; when untreated TC enters the environment, it will cause a negative impact on the human body through the food chain. In the present study, MnO₂/MCM-41@Fe₃O₄ (FeMnMCM) prepared using a hydrothermal and redox method and Camellia oleifera shell-activated carbon (COFAC) prepared through alkali activation were encapsulated using alginate (ALG) and calcium chloride as a cross-linking matrix to give the composite beads COFAC–FeMnMCM–ALG. The resultant COFAC–FeMnMCM–ALG composite beads were then carefully characterized, showing a high immobilization of MnO₂/MCM-41@Fe₃O₄, with porous COFAC as an effective bioadsorbent for enriching the pollutants in the treated samples. These bead catalysts were subsequently applied to the oxidative degradation of TC in a Fenton oxidation system. Several parameters affecting the degradation were investigated, including the H₂O₂ concentration, catalyst dosage, initial TC concentration, and temperature. A very high catalytic activity towards the degradation of TC was demonstrated. The electron paramagnetic resonance (EPR) and quenching results showed that ·OH and ·O₂⁻ were generated in the system, with ·OH as the main radical species. In addition, the COFAC–FeMnMCM–ALG catalyst exhibited excellent recyclability/reusability. We conclude that the as-prepared COFAC–FeMnMCM–ALG composite beads, which integrate MnO₂ and Fe₃O₄ with bioadsorbents, provide a new idea for the design of catalysts for advanced oxidation processes (AOPs) and have great potential in the Fenton oxidation system to degrade toxic pollutants. Full article

Camellia oleifera fruit shell (COS) is an agricultural waste product generated in large quantities by the seed oil extraction industry. Due to its hierarchical thickness structure, COS shows huge potential in constructing porous carbon materials after thermal chemical modification. Herein, a series of COS biochars were synthesized by a carbonization-activation process and achieved excellent mercury removal performance in an aqueous environment. High-temperature carbonization was found to facilitate lignin removal and porosity generation, while retaining hydroxyl and carbonyl groups available for mercury adsorption. A volume of micropores of 594 × 10⁻³ cm⁻³/g with average pore diameter of 1.7 nm was achieved in activated COS biochar. At 550 °C, an adsorption capacity of 57.6 mg/g was realized in 1 mg/L Hg²⁺ solution under different pH environments. This work provides an alternative adsorbent for removing hazardous materials using sustainable bioresources. Full article

Using Camellia oleifera shell (COS) as a raw material and phosphoric acid as the activator, activated Camellia oleifera shell carbon (COSC-0) was prepared and then modified by Fenton’s reagent (named as COSC-1). SEM, GC-MS, FTIR, and specific surface area and pore analyzers were used to study the adsorption performance of COS, COSC-0, and COSC-1 on cooking fumes. Results showed that COSC-1 was the best adsorbent compared with COS and COSC-0. The adsorption quantity and penetrating time of COSC-1 were 44.04 mg/g and 4.1 h, respectively. Most aldehydes could be adsorbed by COSC-1, which was due to the large number of carbonyl and carboxyl groups generated on the surface of COSC-1 from the action of Fenton’s reagent. The adsorption effect of COSC-1 on different types of pollutants in cooking fumes was analyzed based on the similar compatibility principle. COSC-1 showed a much higher adsorption effect on the strong polarity functional groups than on weak polar groups. The results provide a theoretical basis for the application of Camellia oleifera shell carbon adsorption technology in the treatment of cooking fumes. Full article

A disadvantage of the commercial Raney Ni is that the Ni active sites are prone to leaching and deactivation in the hydrogenation of xylose to xylitol. To explore a more stable and robust catalyst, activated carbon (AC) supported Ni-Re bimetallic catalysts (Ni-Re/AC) were synthesized and used to hydrogenate xylose and hemicellulosic hydrolysate into xylitol under mild reaction conditions. In contrast to the monometallic Ni/AC catalyst, bimetallic Ni-Re/AC exhibited better catalytic performances in the hydrogenation of xylose to xylitol. A high xylitol yield up to 98% was achieved over Ni-Re/AC (n_Ni:n_Re = 1:1) at 140 °C for 1 h. In addition, these bimetallic catalysts also had superior hydrogenation performance in the conversion of the hydrolysate derived from the hydrolysis reaction of the hemicellulose of Camellia oleifera shell. The characterization results showed that the addition of Re led to the formation of Ni-Re alloy and improved the dispersion of Ni active sites. The recycled experimental results revealed that the monometallic Ni and the bimetallic Ni-Re catalysts tended to deactivate, but the introduction of Re was able to remarkably improve the catalyst’s stability and reduce the Ni leaching during the hydrogenation reaction. Full article

Research Highlights: Intensive nitrogen (N) application for agricultural purposes has substantially increased soil nitrous oxide (N₂O) emissions. Agricultural soil has great potential in the reduction of N₂O emissions, and applications of biochar and nitrification inhibitors may be useful for mitigating agricultural soil N₂O emissions. Background and Objectives: Camellia oleifera Abel. is an important woody oil plant in China. However, intensive N input in C. oleifera silviculture has increased the risk of soil N₂O emissions. As an important greenhouse gas, N₂O is characterized by a global warming potential at a 100-year scale that is 265 times that of carbon dioxide. Thus, mitigation of soil N₂O emissions, especially fertilized soils, will be crucial for reducing climate change. Materials and Methods: Here, we conducted an in situ study over 12 months to examine the effects of C. oleifera fruit shell-derived biochar and dicyandiamide (DCD) on soil N₂O emissions from a C. oleifera field with intensive N application. Results: A three-fold increase of cumulative soil N₂O emissions was observed following N application. Cumulative N₂O emissions from the field with N fertilization were reduced by 36% and 44% with biochar and DCD, respectively. While N₂O emissions were slightly deceased by biochar, the decrease was comparable to that by DCD. Conclusions: Results indicated that biochar may mitigate soil N₂O emissions substantially and similarly to DCD under specific conditions. This result should be examined by prolonged and multi-site studies before it can be generalized to broader scales. Full article