Advanced electrochemical membrane technologies for near-complete resource recovery and zero-discharge of urine: Performance optimization and evaluation

Near-complete recovery of phosphorus from fresh human urine: Combining magnesium-air fuel cells with modified granular attapulgite

In light of the urge demand for sustainable development and environmental protection, the recovery of phosphorus from source-separated urine holds great significance. This study proposed a novel approach combining magnesium-air fuel cells (MAFC) with modified granular attapulgite (GAT) to recover phosphorus from urine, producing a bulk blending fertilizer and soil amendment. The phosphorus adsorption capacity of GAT was enhanced by more than threefold following modification. The combined process attained a phosphorus recovery efficiency of 99.97 %, with the effluent phosphorus concentration decreased to 0.18 mg L-1, which complies with the discharge standard of pollutants for municipal wastewater treatment plant (GB 18918-2002). In practical implementation, the process effectively treated real urine, yielding artificial phosphate ores (APOs) with a struvite content exceeding 88 % and a phosphate purity over 98 %. The pilot-scale assessment indicated a net benefit of 11.29 $·m-3 of urine, demonstrating significant economic feasibility. This work presents an innovative strategy for the efficient recovery of phosphorus from complex wastewater, showcasing its promising potential for practical applications.

Hydrochar-nanocomposite membrane combined hydrothermal pretreatment for nutrient upcycling from anaerobic digestate

Efficient resource recovery is crucial for sustaining food production and alleviating stress on ecosystems. This study combines hydrothermal pretreatment with polyvinylidene fluoride (PVDF)-hydrochar nanocomposite membranes for near-complete resource recovery in kitchen waste treatment. The dual-functionalized pretreatment, which combines targeted conversion/enrichment with adsorption/filtration, effectively addresses the limitations of existing membrane separation technologies, including low nutrient recovery selectivity, low flux, and high costs. Within a wide pH range (3-11), the optimized lanthanum-doped hydrochar demonstrated over 99% phosphorus recovery, alongside exceptional nutrient recovery potential (over 289.71 mg P/g). The innovative composite membrane design successfully processed over 1,000 bed volumes of biogas slurry containing high phosphorus levels across three in-situ rejuvenation cycles, achieving nearly a 30-fold increase in membrane utilization compared to pristine PVDF membranes (36 bed volumes). The durability and fouling resistance of the composite membranes were enhanced through a synergistic mechanism that included ligand exchange and retention, as well as improved membrane surface properties. This facilitated the selective and efficient recovery of nutrients (99.33% P and 50.81% N) and enabled a profitable turnaround for anaerobic by-product upcycling ($28.51/ton). This study offers novel solutions to address the phosphorus scarcity crisis and promotes the integration of organic waste management with low carbon value addition.

Enhanced hybrid capacitive performance for efficient and selective potassium extraction from wastewater: Insights from regulating electrode potential

Prussian blue analogues hold great promise for directly extracting potassium resource from wastewater via hybrid capacitive deionization (HCDI). However, there remain unresolved scientific issues regarding low efficiency and selectivity arising from asymmetric potential distribution induced by spontaneous charge matching. This work systematically investigated the underlying mechanisms for enhancing the storage capacity and specific affinity of representative Berlin Green towards K+ through precise regulation of insertion potential during HCDI operation. Empowered by controlling electrochemical intercalation behaviors, the compatibility between ionic and electronic kinetics was significantly enhanced. Impressive values of 160.12 mg/g, 61.27 %, and 0.07 kWh/mol were achieved under potentiostatic mode (0.1 V vs. Ag/AgCl) for insertion capacity, charge efficiency, and energy consumption, respectively. These results significantly outperformed the optimal levels obtained under constant cell voltage (0.9 V), which were 128.52 mg/g, 47.50 %, and 0.12 kWh/mol, respectively. In both aqueous solution with binary components and urine, the results emphasized the potential of the synergy effect between lattice hindrance and insertion chemistry in promoting intercalation selectivity, with the highest selectivity coefficients of 28.35 (K+/Na+), 76.22 (K+/Ca2+) and 175.12 (K+/Mg2+), respectively. The presented concept-to-proof offers a versatile approach for the advancement of high-performance HCDI and paves the way towards its sustainable application in nutrient recycling from natural waters or wastewaters.