Soil amendment with biochar is evaluated globally as a means to improve soil fertility and to mitigate climate change. However, the effects of biochar on soil biota have received much less attention than its effects on soil chemical properties. A review of the literature reveals a significant number of early studies on biochar-type materials as soil amendments either for managing pathogens, as inoculant carriers or for manipulative experiments to sorb signaling compounds or toxins. However, no studies exist in the soil biologyliterature that recognize the observed largevariations ofbiochar physico-chemical properties. This shortcoming has hampered insight into mechanisms by which biochar influences soil microorganisms, fauna and plant roots. Additional factors limiting meaningful interpretation of many datasets are the clearly demonstrated sorption properties that interfere with standard extraction procedures for soil microbial biomass or enzyme assays, and the confounding effects of varying amounts of minerals. In most studies, microbial biomass has been found to increase as a result of biochar additions, with significant changes in microbial community composition and enzyme activities that may explain biogeochemical effects of biochar on element cycles, plant pathogens, and crop growth. Yet, very little is known about the mechanisms through which biochar affects microbial abundance and community composition. The effects of biochar on soil fauna are even less understood than its effects on microorganisms, apart from several notable studies on earthworms. It is clear, however, that sorption phenomena, pH and physical properties of biochars such as pore structure, surface area and mineral matter play important roles in determining how different biochars affect soil biota. Observations on microbial dynamics lead to the conclusion of a possible improved resource use due to co-location of various resources in and around biochars. Sorption and therebyinactivation of growth-inhibiting substances likelyplaysa rolefor increased abundance of soil biota. No evidence exists so far for direct negative effects of biochars on plant roots. Occasionally observed decreases in abundance of mycorrhizal fungi are likely caused by concomitant increases in nutrient availability,reducing theneedfor symbionts.Inthe shortterm,therelease ofavarietyoforganic molecules from fresh biochar may in some cases be responsible for increases or decreases in abundance and activity of soil biota. A road map for future biochar research must include a systematic appreciation of different biochar-types and basic manipulative experiments that unambiguously identify the interactions between biochar and soil biota.

http://www.css.cornell.edu/faculty/lehmann/pictures/publ/SoilBiolBiochem%2043,%201812–1836,%202011%20Lehmann.pdf

Biochar effects on soil biota – A review

Arsenic removal from water/wastewater using adsorbents—A critical review

Activated carbons and low cost adsorbents for remediation of tri- and hexavalent chromium from water.

https://www.dora.lib4ri.ch/eawag/islandora/object/eawag%3A7182/datastream/PDF2/Michael-2013-Urban_wastewater_treatment_plants_as-%28accepted_version%29.pdf

Urban wastewater treatment plants as hotspots for the release of antibiotics in the environment: a review

The characterization of activated carbons with oxygen and nitrogen surface groups

Pharmaceuticals as emerging contaminants and their removal from water. A review

A series of activated carbons with different degrees of activation was treated with HNO 3 , H 2 O 2 , and (NH 4 ) 2 S 2 O 8 in order to introduce oxygen surface complexes. The effects of the oxidizing treatments on the surface area, the pore texture, and the surface chemical nature were analyzed by means of N 2 and CO 2 adsorption, mercury porosimetry, FTIR, TPD, electrophoretic, and mass titration measurements. Results obtained show that the HNO 3 treatment affects the surface area and the porosity of the samples to a greater extent than the other treatments. Carboxyl groups were essentially fixed after the three treatments, although ketone and ether groups, as detected by FTIR, were also fixed after the treatments with peroxides. The most important conclusion was that the stronger acid groups were fixed after the (NH4) 2 S 2 O 5 treatment rather than after the HNO 3 treatment, in spite of the fact that this latter treatment fixed the largest number of oxygen complexes that evolved as CO 2 .

Activated Carbon Surface Modifications by Nitric Acid, Hydrogen Peroxide, and Ammonium Peroxydisulfate Treatments

The adsorption of Escherichia coli on different activated carbons has been studied. The activated carbon samples used have been characterized, determining their surface area, pore size distribution, elemental analysis, mineral matter analysis and pH of the point of zero charge. The adsorption capacity of these carbons increased with their hydrophobicity and macropore volume. The number of bacteria adsorbed on the demineralized activated carbon in a solution of pH value equal to the iso-electric point of the carbon was negligible. However, in the presence of cations the proportions of bacterial cells adsorbed were 87.8% (Fe3+), 54.7% (Ca2+) and 24.8% (Mg2+) respectively. This increase in adsorption capacity in the presence of electrolytes has been explained on the basis of both the reduction in electrostatic free energy and the increase in cell surface hydrophobicity due to the metal bound by some compounds of the cell membrane. When the solution pH was intermediate between the pH values of the point of zero charge of the carbon and bacteria the number of bacteria adsorbed increased due to the attractive interactions between the carbon and bacteria. The adsorption of bacteria on activated carbons decreased the porosity and increased the negative charge density of the latter. Depending on the experimental conditions used, the presence of bacteria can enhance the capacity of activated carbons to adsorb lead.

© 2001 Society of Chemical Industry

Activated carbon surface modifications by adsorption of bacteria and their effect on aqueous lead adsorption

The present study aimed to analyze the behavior of different activated carbons in the adsorption and removal of bisphenol A (2−2-bis-4-hydroxypheniyl propane) from aqueous solutions in order to identify the parameters that determine this process. Two commercial activated carbons and one prepared in our laboratory from almond shells were used; they were texturally and chemically characterized, obtaining the surface area, pore size distribution, mineral matter content, elemental analysis, oxygen surface groups, and pH of the point of zero charge (pHPZC), among other parameters. Adsorption isotherms of bisphenol A and adsorption capacities were obtained. The capacity of the carbons to remove bisphenol A was related to their characteristics. Thus, the adsorption of bisphenol A on activated carbon fundamentally depends on the chemical nature of the carbon surface and the pH of the solution. The most favorable experimental conditions for this process are those in which the net charge density of the carbon is ze...

M.A. Ferro-García

Papers

Pharmaceuticals as emerging contaminants and their removal from water. A review

Activated Carbon Surface Modifications by Nitric Acid, Hydrogen Peroxide, and Ammonium Peroxydisulfate Treatments

Activated carbon surface modifications by adsorption of bacteria and their effect on aqueous lead adsorption

Bisphenol A removal from water by activated carbon. Effects of carbon characteristics and solution chemistry.

Removal of nitroimidazole antibiotics from aqueous solution by adsorption/bioadsorption on activated carbon