Additive manufacturing of biodegradable magnesium implants and scaffolds: Review of the recent advances and research trends

Synthetic grafting needs improvements to eliminate secondary surgeries for the removal of implants after healing of the defected tissues.Tissue scaffolds are engineered to serve as temporary templates,which support the affected tissue and gradually degrade through the healing period.Beside mechanical function to withstand the anatomic loading conditions,scaffolds should also provide a decent biological function for the diffusion of nutrients and oxygen to the cells,and excretion of the wastes from the cells to promote the new tissue growth and vascularization.Moreover,the degradation byproducts of the scaffolds should be safe to the human body.Development of such multifunctional scaffolds requires selection of the right material,design,and manufacturing method.Mg has been recognized as the prominent biodegradable metal with regards to its mechanical properties matching to that of human bone,degradability in the body fluid,and its ability to stimulate new tissue growth.Scaffolds with intricate porous structures can be designed according to the patient-specific anatomic data using computer aided designs.Additive manufacturing(AM)is the right method to materialize these models rapidly with reasonably acceptable range of dimensional accuracy.Thus,the recent research trend is to develop ideal scaffolds using biodegradable Mg through AM methods.This review compiles and discusses the available literature on the AM of biodegradable Mg parts from the viewpoints of material compositions,process conditions,formation quality,dimensional accuracy,microstructure,biodegradation,and mechanical properties.The current achievements are summarized together,and future research directions are identified to promote clinical applications of biodegradable Mg through the advancement of AM.

Equilibrium and kinetics of copper ions removal from wastewater by ion exchange

The removal of copper ions from wastewater by ion exchange has been studied using an iminodiacetate resin.The capacity of the resin for the copper ions has been determined to be 2.30 mmol·g^(-1) by measuring the equilibrium isotherm at 25 °C and initial pH value of 3.5 where the final equilibrium p H value is 5. An analysis of equilibrium isotherm models showed that the best fit model was the Langmuir–Freundlich. The kinetics of the ion exchange process have been investigated and four kinetic models have been tested namely: Ritchie model, pseudo-second order model, pseudo-first order model and the Elovich model. The pseudo-second order model provides the best fit to the kinetic data.

Construction of robust and durable Cu_(2)Se-V_(2)O_(5) nanosheet electrocatalyst for alkaline oxygen evolution reaction

Reducing the production costs of clean energy carriers such as hydrogen through scalable water electrolysis is a potential solution for advancing the hydrogen economy.Among the various material candidates,our group demonstrated transition-metal-based materials with tunable electronic characteristics,various phases,and earth-abundance.Herein,electrochemical water oxidation using Cu_(2)Se-V_(2)O_(5) as a non-precious metallic electrocatalyst via a hydrothermal approach is reported.The water-splitting performance of all the fabricated electrocatalysts was evaluated after direct growth on a stainless-steel substrate.The electrochemically tuned Cu_(2)Se-V_(2)O_(5) catalyst exhibited a reduced overpotential of 128 mV and provided a reduced Tafel slope of 57 mV·dec^(−1) to meet the maximum current density of 250 mA·cm^(−2).The optimized strategy for interfacial coupling of the fabricated Cu_(2)Se-V_(2)O_(5) catalyst resulted in a porous structure with accessible active sites,which enabled adsorption of the intermediates and afforded an effective charge transfer rate for promoting the oxygen evolution reaction.Furthermore,the combined effect of the catalyst components provided long-term stability for over 110 h in an alkaline solution,which makes the catalyst promising for large-scale practical applications.The aforementioned advantages of the composite catalyst overcome the limitations of low conductivity,agglomeration,and poor stability of the pure catalysts(Cu2Se and V2O5).

A review of recent developments in CO_(2) mobility control in enhanced oil recovery

Carbon dioxide-enhanced oil recovery(CO_(2)-EOR)has gained widespread attention in light of the declining conventional oil reserves.Moreover,CO_(2)-EOR contributes to the reduction of the global emissions of greenhouse gases through CO_(2) sequestration in subsurface geologic formations.This method has been largely used in the petroleum industry for several decades especially for extracting oil from light-to-medium oil reservoirs approaching an advanced state of maturity.Traditionally,CO_(2) is used in a continuous flooding scheme for EOR.However,continuous CO_(2) flooding tends to be problematic due to unfavorable mobility,viscous fingering/channeling and early breakthrough of CO_(2),especially in the presence of reservoir heterogeneities.In this paper,recent developments in the methods used to overcome these problems are reviewed.These developments include CO_(2)water-alternating-gas(WAG)injection,polymer-assisted CO_(2) injection,surfactant-assisted CO_(2) mobility control(CO_(2)-foam injection),and nanoparticle-assisted CO_(2) flooding.Each method addresses,to an extent,one or more of the problems associated with conventional CO_(2) flooding.Furthermore,incorporating more than one method can provide better performance in terms of CO_(2) mobility control and oil recovery.In comparison with CO_(2)-WAG and CO_(2)-foam injection methods,the use of polymers and nanoparticles with CO_(2) flooding is relatively new.These two new methods were mostly investigated experimentally,at the laboratory level,and they still need further development prior to field implementation.

Ozone and ozone/hydrogen peroxide treatment to remove gemfibrozil and ibuprofen from treated sewage effluent: Factors influencing bromate formation

Reuse of treated sewage effluent is an important option to overcome water scarcity.Conventional wastewater treatment methods are inadequate for the removal of several persistent contaminants such as pharmaceuticals and personal care products(PPCPs).In this study the removal of ibuprofen and gemfibrozil by ozonation and ozone/hydrogen peroxide(O3/H2O2)advanced oxidation process(AOP),as well as the formation of bromate were investigated at different temperatures and pH values.Complete removal of gemfibrozil and a maximum of 80%ibuprofen removal were achieved using ozone dosage of 1.5 mg/L with O3:H2O2 ratio of 1:0.25 in the O3/H2O2 process.The effect of temperature on the removal efficiency of these two compounds was found to be negligible from 25 to 40ᵒC for both processes.pH effect from 6 to 9 was also found to be negligible for gemfibrozil removal,while ibuprofen had relatively lower removal by ozonation at pH 6 compared to higher pH values.Bromate formation was decreased to 0.012 mg/L when the pH was increased to 9.Increasing the temperature to 40ᵒC also resulted in less bromate formation which was the lowest value obtained in this study at 0.0102 mg/L.Addition of H2O2 did not affect the formation of bromate and in some cases it was found to be slightly higher compared with ozonation treatment.

Mixed plastics waste valorization to high-added value products via thermally induced phase separation and spin-casting

Plastic waste is an underutilized resource that has the potential to be transformed into value-added materials.However,its chemical diversity leads to cost-intensive sorting techniques,limiting recycling and upcycling opportunities.Herein,we report an open-loop recycling method to produce graded feedstock from mixed polyolefins waste,which makes up 60%of total plastic waste.The method uses heat flow scanning to quantify the composition of plastic waste and resolves its compatibility through controlled dissolution.The resulting feedstock is then used to synthesize blended pellets,porous sorbents,and superhydrophobic coatings via thermally induced phase separation and spin-casting.The hybrid approach broadens the opportunities for reusing plastic waste,which is a step towards creating a more circular economy and better waste management practices.

Biochar from vegetable wastes:agro-environmental characterization

Considering the global issue of vegetable wastes generation and its impact on the environment and resources,this study evalu-ated the conversion of four largely produced vegetable wastes(cauliflower,cabbage,banana peels and corn cob residues)into biochar.Each waste was tested individually and as a combined blend to assess feedstock influences on biochar properties.In addition,various pyrolysis temperatures ranging from 300℃ to 600℃ and two particle size fractions(less than 75μm,75-125μm)were considered.Biochars were characterized for various properties that can influence the biochars’effective-ness as a soil amendment.It was found that pyrolysis temperature was the most dominant factor on biochar properties,but that individual feedstocks produced biochars with different characteristics.The biochars had characteristics that varied as follows:pH 7.2-11.6,ECE 0.15-1.00 mS cm^(−1),CEC 17-cmolc kg^(−1)andζ-potential−0.24 to−43 mV.Based on optimal values of these parameters from the literature,cauliflower and banana peels were determined to be the best feedstocks,though mixed vegetable waste also produced good characteristics.The optimum temperature for pyrolysis was around 400℃,but differed slightly(300-500℃)depending on the distinct feedstock.However,smaller particle size of biochar application was always optimal.Biochar yields were in the range of 20-30%at this temperature range,except for corn cobs which were higher.This study demonstrates that pyrolysis of dried vegetable wastes is a suitable waste valorization approach to produce biochar with good agricultural properties.