Black
liquor (BL) concentration by multieffect evaporation is an
extremely energy-intensive operation in the kraft pulping cycle. Membranes
can significantly save energy in this process, but conventional membranes
are strongly challenged by low solute rejections and poor stability
in BL, which is a complex mixture containing dissolved lignin, other
nonlignin organics, multiple inorganic salts at highly alkaline pH,
and process temperatures of 70–85 °C. Here we describe
in detail the fabrication, modification, and characterization of robust
and high-performance graphene oxide (GO) nanofiltration membranes
for BL concentration. We show that poly(ether sulfone) (PES)-supported
GO membranes prepared from chemically reduced GO, and then subjected
to high-pressure hydraulic compaction, show excellent chemical and
mechanical stability under real BL conditions in comparison to conventional
GO membranes. These membranes (referred to as “GO-3”
in this work) show near-perfect (>99%) lignin rejection, high total
organic carbon (TOC) rejection (up to 93%), and greatly improved inorganic
rejections especially for divalent anions that are predominant in
BL. Finally, the GO-3 membranes are scaled up on larger PES sheets
(∼660 cm2 in size) and are operated under realistic
cross-flow conditions with real BL feed flow rates as high as 10 L/min
at 70 °C. The GO-3 membranes show robust performance over more
than 1500 h (60 days) of continuous operation in multiple cycles of
10–50 bar transmembrane pressures, attaining stable and sustained
permeate fluxes as high as 25 LMH and excellent rejection performance
equal to that obtained at smaller scale. The main results of this
work have strong implications on the development of membrane processes
for BL dewatering and more generally for processing of complex biorefinery
feed streams.
Rechargeable batteries using aqueous electrolyte have intrinsically low flammability and are promising alternatives to lithium ion batteries for mid-and large-scale energy storages. Among aqueous battery anode materials, zinc metal stands out because of the highest energies (5846 Ah/L volumetric capacity, 3 times the amount of a lithium metal anode) and an operating potential near the lower limit of water stability window. However, the rechargeability of Zn anodes is hindered by passivation and dissolution problems associated with the solid-solute-solid transformation during cycling. Here we solve both problems simultaneously by designing a distinctive nanostructured zinc anode in which 100 nm ZnO nanoparticles are wrapped and segmented by graphene oxide (GO) sheets. The small size of primary ZnO nanoparticles prevents passivation, while the GO wrap and segmentation confine soluble Zn(OH) 4 2− intermediates from escaping. This lasagna-like nanostructured Zn anode measured a high volumetric capacity of 2308 Ah/L and achieved a remarkable capacity retention of 86% after 150 cycles. In contrast, the open-structured ZnO nanoparticle anode, without the protection of GO, completely died after 90 cycles.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.