Type-wide biochars loaded with Mg/Al layered double hydroxide as adsorbent for phosphate and mixed heavy metal ions in water.

This study discussed the adsorption of mixed heavy metal ions (Cu2+, Co2+, Pb2+) and phosphate ions by ten pristine biochars and those with precipitated Mg/Al layered double hydroxide (LDH). The pristine biochars have adsorption capacities of 6.9-13.4 mg/g for Cu2+, 1.1-9.7 mg/g for Co2+, 7.8-20.7 mg/g for Pb2+, and 0.8-4.9 mg/g for PO43-. The LDH-biochars have markedly increased adsorption capacities of 20.4-25.8 mg/g for Cu2+, 8.6-15.0 mg/g for Co2+, 26.5-40.4 mg/g for Pb2+ with mixed metal ions, and 13.0-21.8 mg/g for PO43-. Part of the Mg ions but Al ions are released from the LDH-biochars during adsorption, counting less than 7.2% of the adsorbed ions. The pristine biochars have specific adsorption sites for Cu2+ and Co2+, separate Pb2+ sites related to ether groups on biochar, and areal-dependent sites for PO43-. There is no universal adsorption mechanism corresponding to mixed metal ion adsorption for individual pristine biochar involving different contributions of C-O-C, C-O-H, and CO groups and graphitic-N, pyrrolic-N, and pyridine-N groups. The LDH complexes with hydroxyl and carbonyl groups of biochar, and the LDH interacts with biochar's ether groups, which contributes to metal adsorption, against the conception that the biochar is merely a carrier of LDH as adsorbents.

Manganese ferrite modified agricultural waste-derived biochars for copper ions adsorption.

Biochar is an eco-friendly, low-cost, and carbon-rich material. This study synthesized the biochars from three agricultural wastes, pinecone, white popinac, and sugarcane bagasse, and then modified them by manganese ferrite (MnFe2O4) co-precipitation. These biochars were applied as adsorbents for the removal of Cu(II) ions from water. All three different MnFe2O4-biochars have similar adsorption performances: rapid adsorption kinetics with equilibrium being reached within 5 hr of contact and significantly enhanced adsorption capacities of Cu(II) ions from water. The principal adsorption mechanisms were identified as complexation reactions, contributed by the carboxyl and hydroxyl groups by pristine biochars and by the Mn-O and Fe-O groups for all three MnFe2O4-biochars. The MnFe2O4-biochars can be reused for three cycles, with the maximum adsorption capacities of Cu(II) of the regenerated biochars declining with the loss of precipitated MnFe2O4.

Pristine and manganese ferrite modified biochars for copper ion adsorption: Type-wide comparison.

This study synthesized nine biochars from different feedstocks and chemically modified their surfaces using MnFe2O4 precipitation at pH 11 (MnFe2O4-biochars). The maximum adsorption quantities (qmax) of Cu(II) at pH 6 and 25 °C for pristine biochars based on Langmuir model ranged 10.4-23.6 mg/g and for MnFe2O4-biochars, 32.7-43.1 mg/g, with enhancement from 65.6% (bamboo biochar) to 246% (white popinac biochar). Type-wide comparison shows no correlation between surface area of pristine or MnFe2O4-biochars on the adsorption performance. Conversely, the carboxyl groups on the nine biochar surfaces have contributed to Cu(II) adsorption. The type-dependence for qmax of different MnFe2O4-biochars becomes insignificant, confirming the role of biochars being principally an oxide carrier instead of an adsorbent.

Three Output Membrane Hydrocyclone: Classification and Filtration.

In this study, through simulation and experimental verification, we proposed a novel hydrocyclone in which a tubular ceramic membrane passed through the overflow outlet to the underflow outlet. The centers of overflow and underflow outlets were tubular membranes equipped with an exit of outside-in filtration, and the overflow the underflow outlets were shaped into annular (donut shape) exits. Thus, this novel hydrocyclone has three outlets, namely the overflow dilute liquid, the underflow concentrated liquid, and clear filtrate. This system enabled higher dilution of hydrocyclone overflow concentration than that in the traditional system. Furthermore, underflow was more concentrated, and we obtained a clear filtrate. Therefore, this device can simultaneously perform classification and filtration, which is valuable for special liquid recycling. For instance, in wafer cutting fluid recovery in solar energy processes, the fluid with more silicon can function as the overflow, the fluid with more silicon carbide can function as the underflow, and the polyethylene glycol (PEG) organic solvent can function as the clear filtrate.

Network strength and dewaterability of flocculated activated sludge.

Works in literature proposed the use of the rheological properties of wastewater sludges as an index for conditioner assessment and control. We demonstrated in this work, on the contrary, that one could not justify the consistency of the commonly used rheological characteristics of the sewage sludge samples taken from the same site but at different dates. A physically relevant index was proposed instead for describing the total network strength, which was hypothesized to correlate the dewatering efficiency of flocculated sludge. Based on this index, the network of a sludge was demonstrated to be largely destroyed after shearing, while the relaxation in an unbound environment or mild pouring over action could partially reinstall the structure. Moreover, a uniform shear rate field could produce network of greater strength when compared with that conditioned in a stirred tank.