Advanced clay sorbents have attracted widespread attentions for applications in environment remediation and pollution control. Here, a facile and environmentally-friendly approach to synthesizing a porous Na-bentonite/ hickory-biochar composite sorbent from hickory waste biomass using hand-milling and carbon-bed pyrolysis was investigated. The sorbents, made using a range of clay/biomass ratios and at a range of temperatures, were characterized and examined for their ability to remove Eriochrome blue black R (EBBR) anionic organic dyes from aqueous solution. The composite sorbents showed increased microporosity and O-containing functional groups over the pyrolyzed bentonite control. The composite prepared with 10% biomass by weight, and at 600 degrees C had the greatest EBBR adsorption, and was best fit to Freundlich isotherm and intraparticle diffusion kinetics models. The modeled maximum EBBR sorption capacity of this composite (2020.5 mg g-1, R2 adj = 0.92), which was attributed to the dispersion of bentonite particles over the biochar surface. These results show the bentonite/ biochar composite to have great potential for use in environmental remediation applications.

Improving the adsorption ability of layered double hydroxide (LDH) has been considered as a promising strategy to promote its photodegradation of aqueous pollutants. In this work, nickel-aluminium layered double hydroxides (NiAl-LDH)/biochar nanocomposites were prepared using a simple coprecipitation method, and then applied in synergistic adsorption-photodegradation of tetracycline (TC) in aqueous solutions. In addition, the governing TC removal mechanisms by the nanocomposites were revealed. All NiAl-LDH/BC samples showed strong adsorption and photodegradation of TC. The Langmuir maximum TC adsorption capacity of optimized NiAl-LDH/BC-0.5 reached 124.2 mg/g, which was much better than that of NiAl-LDH (56.1 mg/g) and biochar (11.1 mg/g). Besides, TC photodegradation rate constant of NiAl/BC-0.5 was 3.6 and 4.4 times of that of NiAl-LDH and BC, respectively. The NiAl/BC-0.5 exhibited the maximum TC adsorption-photodegradation efficiency 94.4% in 90 min compared to NiAl-LDH (73.7%) and BC (48.2%). The rate constant of modified Elovich kinetic model for synergistic adsorption and photodegradation on NiAl/BC-0.5 (9.477 min-1) was the highest among the composites. The NiAl-LDH/BC had significantly larger BET surface areas than NiAl-LDH and BC. The step scheme (S-scheme) heterostructures were constructed on the interface of BC and NiAl-LDH in nanocomposites, which facilitated the transfer of photo-induced charges. This work demonstrates that combination of NiAl-LDH and biochar can create synergy for TC adsorption-photodegradation, which is a promising and green strategy.

A series of microwave biochars derived from wheat straw in the presence of a granulated activated carbon (GAC) catalyst, using a range of microwave conditions, were produced, characterized and tested as sorbents of three benzene series volatile organic compounds (VOCs). The microwave biochar with the greatest specific surface area (SSA), total pore volume (TPV), and micropore volume (312.62 m(2) g(-1), 0.2218 cm(3) g(-1), and 0.1380 cm(3) g(-1), respectively), were produced with 1:3 biomass:GAC catalyst mass ratio, 10 min microwave irradiation time, and at 500 W power level (WB500). Maximum adsorption capacities of WB500 to benzene, toluene and o-xylene were 53.9 mg g(-1), 75.8 mg g(-1) and 63.0 mg g(-1), respectively, and were directly correlated to microwave biochar properties such as SSA, TPV or micropore volume, but were also influenced by VOC properties such as molecular polarity and boiling point. Kinetic modeling suggested that adsorption was governed by both physical partitioning and chemisorption mechanisms. In addition, microwave biochars maintained 79% to 92% of their initial adsorption capacity after ten adsorption/desorption cycles. These results suggest that microwave biochars produced with an GAC catalyst have excellent potential for efficient use in the removal of VOCs from waste gas.