Critical study of crop-derived biochars for soil amendment and pharmaceutical ecotoxicity reduction

Highlights

• Crop-derived biochar show sorption toward cationic pharmaceuticals.

• The mechanism of sulfonamides sorption was checked.

• The amendment of soil by biochar decrease the toxicity of sulfonamides to cress.

• The toxic effect of biochar to cress by the pH increase was observed.

Abstract

In this study, biochars (BCs) produced from crops (straw and seeds) were tested for the applicability as additive to soils. The effect on pH, water capacity and cation exchange capacity of soil were tested. The ability for the sorption of pharmaceuticals (beta-blockers, anti-inflammatory drugs, sulfonamides, 17α-ethinylestradiol, carbamazepine, caffeine) using the batch sorption test was performed, and the effect of water pH was investigated. In addition, the metals removed from the biochar was analyzed as a potential toxicity factor. The mechanism of adsorption (Langmuir, Freundlich) was tested for sulfadimetoxine. The effect of the rye-derived biochar on water cress germination and the reduction of the sulfonamides toxicity to this plant was tested. The advantages of crop-derived biochar application to different soils (sand soil, clay soil and reference soil) was presented. It was found that tested BCs effectively increase the water capacity of soils, especially sand type soil, but in the same time it had increase the pH of pure-buffering soils. The driving force of pharmaceutical sorption was its ionization form - the highest sorption occurs for cations, medium for neutral forms, while the lowest sorption for anions. The opposite situation have been noted for desorption from biochar. The washing of biochars increases sorption for the neutral and anionic species, but not for the cations. The application of biochars into the soils can from one site protect the plants from toxic impact of sulfonamides, but from the other hamper the root prolongation by the pH increase.

Introduction

Biochar (BC) is the carbon material produced from organic wastes (animals or plants) by pyrolysis. The surface chemistry depend of feeding material and the surface is rich in covalently bonded heteroatoms. The oxygen is present in various forms and share responsibility for the activity of biochar as sorbent for most of chemicals (Benaddi et al., 2000). It possess universal sorption potency (for metals (Harris, 2009; Tchomgui-Kamga et al., 2010), pesticides (Harris, 2009; Liu et al., 2018; Zheng et al., 2010), PAHs (Ahmad et al., 2014; Chen et al., 2008) among others). Thereby there is increasing interest in biochar application for the removal of pollutants from wastewaters or soil remediation. This reflect a graduate increase of scientific report concerning its use (Fig. S1, Supplementary Information). Nevertheless, the constrain the biochar technology in environmental engineering is observed (Fig. S1). The reason is still an insufficient basic knowledge in this area and a concern about the safety of biochar use. The studies of the biochars into soil amendment deal mainly with its positive effects, like retention of phosphor (Matin et al., 2020), improvement of seed germination (Gonzaga et al., 2020), or improvement of mycorrhizal root colonization (Rafique et al., 2020). Nevertheless, the negatives effects were also observed, for example release of heavy metals and PAHs, change in nutrients bioavailability. The reviews of the biochar benefits and limitations for soils can be found in literature (Kavitha et al., 2018; Oliveira et al., 2017; Tan et al., 2017; Yuan et al., 2019). Despite some specific disadvantages the biochar is often described as the promising material for mitigation of soil quality decrease because the anthropogenic pressure.

The area of polar organic contaminants removal from environments thanks to the biochar is in the conceptual phase. After the literature review (Table S1, Supplementary Information) we found that there are few publications which deal with BC as a sorbent for pharmaceuticals as a good example of polar organic pollutants. Most publications focused on single compounds, frequently to those belong to sulfonamides. This study was performed for ten pharmaceuticals (Table S2, Supplementary Information) from various groups; some of them are cations (caffeine (CAF); beta-blockers – atenolol (ATEN), propranolol (PROP), metoprolol (MET)), some anions (sulfonamides – sulfamethoxazole (SMX), and sulfadimetoxine (SDM); non-steroidal anti-inflammatory drugs (NSAIDs) – ibuprofen (IBU) and diclofenac (DIC)), while two of them are neutral (carbamazepine (CAR) and 17α-ethinylestradiol (EE2)) in tested conditions. They represent the pharmaceuticals as a diverse group of new emerging contaminants, and they are often found in wastewater and sludge samples (Stevens, 2007). The applicability of the tested biochars to the soil improvement was determined by test of its impact to the soil physicochemical properties, sorption/desorption of pharmaceuticals, germination of garden cress and reduction of toxicity. The main aim of this study was to check the applicability of newly produced biochar, but also perform the critical discussion of the biochar potential for application into the soils. The aim of test of crop-derived biochar was to found the alternative utility of wastes coming from food production.