Abstract Contamination of aquatic and soil systems by organic and inorganic pollutants has become a serious issue of concern worldwide. Viable and cost-effective solutions are urgently needed to mitigate the negative impacts of diverse pollutants on the environment and human health. Biochar has emerged as an effective and green material for the remediation of a wide spectrum of (in)organic pollutants. However, applications of pristine biochar in decontamination have encountered bottlenecks due to its limited properties which cannot meet the desired remediation requirements. Therefore, multiple modification methods have been developed for tailoring the physicochemical properties of biochar to enhance its effectiveness in environmental decontamination. This work provides a holistic review on the recent advances on the synthesis of engineered biochar using physical, chemical, and biological methods. Further applications and related mechanisms of engineered biochar in the field of environmental decontamination in aquatic and soil systems have also been summarized and discussed. In addition, existing challenges and research gaps are outlined, and future research needs are proposed. This review summarizes the scientific opportunities for a comprehensive understanding of using engineered biochars as effective materials for the remediation of contaminated water and soil. Graphical abstract 

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Engineered biochar for environmental decontamination in aquatic and soil systems: a review

Performance and mechanisms of immobilization remediation for Cd contaminated water and soil by hydroxy ferric combined acid-base modified sepiolite (HyFe/ABsep).

Contamination of paddy soils with arsenic (As) poses imminent threat to the environment and public health. This research work explored the effect of goethite-modified biochar (GMBC) on As immobilization in paddy soil and subsequent accumulation in rice grains. The results showed that the soil supplementation with GMBC significantly improved the biomass of rice plants. In addition, the GMBC application effectively decreased the As content in rice grains (0.72–0.16 mg kg−1). Compared with the control, GMBC 1.5% treatment augmented the iron plaque (Fe-plaque) buildup on rice roots and efficiently sequestered the As by 174%, and reduced its uptake in rice tissues. Soil supplementation with GMBC 1.5% greatly enhanced the activities of soil peroxidase (POD) and catalase (CAT) by 90% and 40%, respectively, compared to the control. Moreover, GMBC amendments improved the relative abundance of the soil bacterial communities and minimized the As mobility in the soil. GMBC 1.5% significantly enhanced the abundance of acidobacteria and Firmicutes by 211% and 95% while that of Chloroflexi decreased by 25%, respectively. The findings of the present investigation demonstrated that GMBC could be used as an environment-friendly approach to remediate As polluted paddy soils and minimize its accumulation in rice grains for mitigation of food security risks and protect public health. 

Elucidating the impact of goethite-modified biochar on arsenic mobility, bioaccumulation in paddy rice (Oryza sativa L.) along with soil enzyme activities

Novel magnetite nano-rods-modified biochar: a promising strategy to control lead mobility and transfer in soil-rice system

Remediation of cadmium or arsenic contaminated water and soil by modified biochar: A review.

Goethite modified biochar simultaneously mitigates the arsenic and cadmium accumulation in paddy rice (Oryza sativa) L

To improve the adsorption capacity of wheat biochar (BC) for arsenic (As), wheat stalks were selected as biomass to generate nano-sized goethite modified biochar (Goethite@BC) by co-precipitation. The adsorption capacities of BC, Goethite, and Goethite@BC for As(Ⅲ) were compared. The samples were analyzed by scanning electron microscopy (SEM) along with energy dispersive spectrometry (EDS), Brunauer-Emmett-Teller (BET), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. The results showed that the nano-goethite coating was uniformly attached to the surface of the BC and improved the surface area and total pore volume of the biochar. The adsorption of As(Ⅲ) by the three adsorbents was proved to fit well with the pseudo-second-order kinetic model and the Langmuir model. Compared to BC, the Goethite@BC increased the adsorption rate of As(Ⅲ) by 62.10 times, and the maximum adsorption capacity of Goethite@BC was 65.20 mg·g-1. The adsorption mechanism of Goethite@BC included non-specific adsorption (electrostatic attraction) and specific adsorption (coordination, complexation, ion exchange, etc.), and nano-goethite particles on the Goethite@BC surface played an important role in the adsorption of As. Goethite@BC has a good application prospects in the field of environmental remediation.

Application of Goethite Modified Biochar for Arsenic Removal from Aqueous Solution

Effects of Cotton Straw Return Time on Carbon Stocks at Subsoil in Saline-Alkaline Soil

In recent years, biochar has attracted considerable attention for soil quality improvement and carbon sequestration due to its unique physicochemical properties. However, the mechanism by which biochar application negatively affects the growth of crop seedlings has not been fully investigated. In this study, a hydroponic experiment was conducted to evaluate the response of rice, wheat, and corn seedlings to biochar application (CK, 0 g/L; BC1, 0.5 g/L; and BC2, 1.0 g/L). Compared with the CK treatment, the BC1 and BC2 treatments decreased the fresh shoot and root weights of rice and corn seedlings (P < 0.05), but there was no significant effect on wheat seedlings (P > 0.05). For the contents of nutrient elements in seedlings, both BC1 and BC2 treatments hindered the roots from absorbing Fe and Cu and increased the uptake of Ca and Mn. Compared with the CK treatment, the translocation factor (TF) values of Ca, Mn, and Zn were significantly decreased especially in rice seedlings (35.3%-36.8%, 68.7%-76.5%, and 29.8%-22.0%, respectively) under the BC1 and BC2 treatments, while only Mn was significantly decreased in wheat and corn seedlings (P < 0.05). Transmission electron microscope (TEM) analysis of root cross-sections showed that nano-sized biochar particles (10∼23 nm) were found in the root cells under BC2 treatment conditions. Our findings reveal that a large amount of biochar application can reduce nutrient absorption and translocation, and hinder rice, wheat, and corn seedlings, particularly rice seedling, in hydroponic system. 

Ying-Jie Yin

Papers

Goethite modified biochar simultaneously mitigates the arsenic and cadmium accumulation in paddy rice (Oryza sativa) L

Application of Goethite Modified Biochar for Arsenic Removal from Aqueous Solution

Effects of Cotton Straw Return Time on Carbon Stocks at Subsoil in Saline-Alkaline Soil

Effect of biochar application on rice, wheat, and corn seedlings in hydroponic culture