Green synthesis of graphite-based photo-Fenton nanocatalyst from waste tar via a self-reduction and solvent-free strategy.

Thermochemical conversion of biomass yields large quantities of tar as a by-product, which is a potential precursor for the synthesis of renewable carbon-based functional materials. In this study, high-performance photo-Fenton catalyst of graphite­carbon-supported iron nanoparticles was synthesized using a self-reduction and solvent-free approach. The results showed that the tar-derived catalyst had unique properties including a defect-rich graphitic structure, high surface area, and an abundant porous structure resulting from the inherent properties of biomass tar. The iron nanoparticles were highly dispersed within the prepared catalysts and were stably anchored on the carbonaceous surface by the FeC bond. The prepared nanocatalyst showed the highest decomposition constant (91.87 × 10-3 min-1) for 20 mM H2O2, and 40 mg/L RhB can be completely degraded within 2 h under catalyst dosage of 1 g/L and H2O2 addition of 20 mM. The degradation mechanism under the photo-Fenton catalyst/H2O2/light system included the heterogeneous Fenton reaction of iron nanoparticles and photo-Fenton reaction of iron oxide, and the efficient RhB degradation was mainly ascribed to the heterogeneous Fenton reaction. In addition, recycling and leaching tests demonstrated that the photo-Fenton catalyst had excellent reusability and stability, where only 7.3% catalytic reactivity was reduced after five cycles. This work provided a green, sustainable, and facile approach for synthesizing photo-Fenton catalysts by value-added utilization of tar wastes.

Efficient immobilization of toxic heavy metals in multi-contaminated agricultural soils by amino-functionalized hydrochar: Performance, plant responses and immobilization mechanisms.

A novel amino-functionalized hydrochar material (referred to NH2-HCs) was prepared and used as the soil amendment to immobilize multi-contaminated soils for the first time. The results showed that the application of NH2-HCs significantly improved (P < 0.05) soil properties (i.e., pH value, cation exchange capacity and organic content). By introduction of NH2-HCs, the contaminated soil showed the highest value of 96.2%, 52.2% and 15.5% reductions in Cu, Pb and Cd bioavailable concentrations and the leaching toxicity of Cu, Pb and Cd were remarkably reduced by 98.1%, 31.3% and 30.4%, respectively. Most of exchangeable Cu, Pb and Cd reduced were transformed into its less available forms of oxidizable and residual fractions. Potential ecological risk assessment indicated that the element Cd accounted for the most of total risks in NH2-HCs amended soils. The mechanism study indicated that surface complexation, chemical chelating and cation-pi interaction of NH2-HCs played a vital role in the immobilization of heavy metals. Pot experiments further verified that the application of NH2-HCs significantly improved plant growth and reduced metal accumulations. The present study offered a novel approach to prepare amino-functionalized hydrochars with great potential as the green and alternative amendments for efficiently immobilizing heavy metals in multi-contaminated soil.

New use for spent coffee ground as an adsorbent for tetracycline removal in water.

Spent coffee grounds (SCG-1 and SCG-2) were used to study the adsorption of tetracycline (TC) antibiotics and the effects of adsorption time, initial pH, amount of adsorbent and ionic strength were detected. The TC adsorption isotherm on SCG-1 was compared with SCG-2. The results showed that the removal efficiencies of TC (50 mg/L) of SCG-1 and SCG-2 were 83.1% and 97.2%, respectively, shake for 2 h. The probability of adsorption is high and balances in about 20 min. The estimate of parameters got for TC from the Langmuir isotherm saturated adsorption quantity and adsorption balance constant were 64.89 mg/g, 0.0557 L/mg, respectively for SCG-1 and 123.46 mg/g, 0.4735 L/mg, respectively for SCG-2. The adsorption mechanism might be a π-π interaction that occurs in the interface by hydrogen bonding and the between the TC molecular and the SCGs. At last, we found that SCG has a high adsorption size for TC.

Utilizations of agricultural waste as adsorbent for the removal of contaminants: A review.

In recent years, various industrial activities have caused serious pollution to the environment. Due to the low operating costs and high flexibility, adsorption is considered as one of the most effective technologies for pollutant management. Agricultural waste has loose and porous structures, and contains functional groups such as the carboxyl group and hydroxyl group, so it can be invoked as biological adsorption material. Agricultural waste gets the advantages of a wide range of sources, low cost, and renewable. It has a good prospect for the comprehensive utilization of resources when used for environmental pollution control. This article summarized the current research status of agricultural waste in adsorbing pollutants, which pointed out the influencing factors of adsorption, expounded the adsorption mechanism of biological adsorption and introduced the related parameters of adsorption, proposed the application of adsorbents in engineering including adsorption in liquid and gas phases, at the same time it gave the future development prospect of agricultural waste as adsorbent.