Water pollution is one of the global challenges that society must address in the 21st century aiming to improve water quality and reduce human and ecosystem health impacts. Industrialization, climate change, and expansion of urban areas produce a variety of water pollutants. In this work, we discuss some of the most recent and relevant findings related to the release of heavy metals, the possible risks for the environment and human health, the materials and technologies available for their removal. Anthropogenic activities are identified as the main source of the increasing amounts of heavy metals found in aquatic environments. Some of the health hazards derived from repeated exposure to traces of heavy metals, including lead, cadmium, mercury, and arsenic, are outlined. We also give some perspectives about several techniques used to detect heavy metals, as well as about the factors that could affect the contaminant removal. The advantages and drawbacks of conventional and non-conventional heavy metal removal methods are critically discussed, given particular attention to those related to adsorption, nanostructured materials and plant-mediated remediation. Some of the commercial products currently used to eliminate heavy metals from water are also listed. Finally, we point out some the requirements and opportunities linked to developing efficient methods for heavy metal removal, such as the ones that exploit nanotechnologies.

Heavy metal water pollution: A fresh look about hazards, novel and conventional remediation methods

Olive stones have been widely used as a renewable energy biowaste source. As they are rich in elemental carbon (40–45 wt%), much research focussed on effectively converting olive stones, as precursors, into activated carbon adsorbents. However, only a few studies have concentrated on summarising the various techniques used to produce activated carbon from olive stone. This article reviews the research undertaken on the production and application of activated carbon as an adsorbent from olive stones for wastewater treatment. Various physical, chemical and physico-chemical treatments to remove heavy metals, organics and dyes are discussed, and the resultant adsorption capacities are reported. In several cases, very high adsorption capacities are recorded. Finally, the future prospects of these materials as adsorbents are discussed, and after further development work, olive stone-derived activated carbons have great potential especially in the area of organic polluted wastewaters.

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Production and applications of activated carbons as adsorbents from olive stones

Heavy metal contamination has been a serious threat to environment and human health Carbon-based materials, from biochar/activated carbon to modified materials (ie carbon nanotubes-based materials, and graphene-based materials), have been widely studied as efficient adsorbents for the heavy metal removal from aqueous solutions This review discussed the recent achievements in adsorption isotherms, adsorption kinetics and adsorption mechanism according to the existing forms of heavy metals in water The effect of process conditions, such as temperature, pH value, and coexisting ions, on adsorption performance are combed, and the universal guidance law is obtained The physical adsorption, electrostatic interaction, ion exchange, surface complexation, and precipitation/coprecipitation play important roles in heavy metals adsorption process In addition to the common activated carbon(AC), biochar(BC) and the emerging carbon nanotubes(CNTs) and graphene(GN) adsorbent show good development potentials Meanwhile, though the modified carbonaceous materials can achieve high adsorption capacity and removal efficiency of heavy metals, the modification operation is complex, especially chemical modification Acid and alkali solution are often used to regenerate spent materials in desorption, however, further studies of other desorption reagent are really needed This review highlights the removal of heavy metal ions from aqueous solution using carbon-based materials as adsorbents, and discusses the existing deficiencies and suggestions on further study

Removal of heavy metals from aqueous solution using carbon-based adsorbents: A review

Wastewater contains many organic and inorganic pollutants and discharging them into received waters leads to serious environmental problems. The wastewater that is produced from various industries contains a noticeable amount of dyes; heavy metals and metalloids this has remained one of the major environmental problems facing public health. Unfortunately, the conventional wastewater remediation process is unable to remove dyes and heavy metals completely. One of the widely used water treatment technologies is biosorption, biosorbents are considered to be an emerging green, cost-effective, and efficient alternative. Therefore, the search for locally or regionally available biomasses for heavy metals/metalloids and dyes removal gained rapid attention. Methylene blue, Crystal violet, Reactive black 5, and Congo red; Cd, Cr, Cu, Pb, Hg, Ni, and Zn; and As were selected as examples for dyes, heavy metals, and metalloids, respectively, In this regard, a comprehensive understanding of the biosorption capability of different biosorbents is necessary to know how they can remove inorganic and organic contaminants in wastewater. Biosorption is an ion exchange, complexation, and coordination process. Besides, the recent advances in various biomaterials-based biosorbents and different approaches of pollutants removal from wastewater with several examples to provide a backdrop for future research have been reviewed. This can be beneficial for developing more effective technologies to eliminate contaminants, thus bridging the gap between laboratory results and industrial use. crustacean shells, algae, chitosan are the most effective biosorbents. These biosorbents can serve as good alternatives to synthetic materials for pollutants removal from wastewater.

A critical review of biosorption of dyes, heavy metals and metalloids from wastewater as an efficient and green process

https://pureadmin.qub.ac.uk/ws/files/190290035/water_treatment_revised_Review_Accepted_for_publication.pdf

Insight on water remediation application using magnetic nanomaterials and biosorbents

Typical chemical precipitation methods using lime (Ca(OH)2), soda ash (Na2CO3) and sodium sulfide (Na2S) for removals of heavy metals (i.e. Zn (II), Cu (II) and Pb (II)) from aqueous solutions were compared by jar tests. A focus was especially given to particle size differences and chemical phase conversion of precipitates. A removal of 99.99% from aqueous solutions with three precipitants was achieved for copper and zinc at an initial concentration of 100 mg/L. And lead was efficiently removed (99.75%) by sodium sulfide. In contrast, the maximal lead removals with lime or soda ash precipitation were only 76.14% and 97.78%. The mean particle size of precipitates was in the range of 55 nm–45 μm, depending on properties of precipitants and heavy metal to precipitant ratios. The settling performance of the sludge derived from precipitation was dominated by particle size and Zeta-potential of precipitates. It was observed that ultra-fine copper sulfide particles resulted from the precipitation were around 55 nm and did not settle in 12 h due to electrostatic repulsion force between particles. The main compounds in the sludge obtained from precipitation were metal hydroxides and metal sulfides. However, spontaneous dehydration of metal hydroxide, oxidation of sulfide and atmospheric carbonation were identified by means of XRD and thermal analyses, which is invaluable to the disposal and utilization of the sludge.

Comparison of heavy metal removals from aqueous solutions by chemical precipitation and characteristics of precipitates

Bimetallic Au-decorated Pd catalyst for the liquid phase hydrodechlorination of 2,4-dichlorophenol

Four kinds of iron-bearing materials including chalcopyrite, pyrite, sponge iron and iron–carbon composite were exploited as catalysts and 3D electrodes (particle electrode) for heterogeneous electro-Fenton oxidation processes. Their catalytic activities were compared according to decolorization (i.e. 1 − C ∕ C 0) and COD removal efficacies, using Reactive Red X-3B as a model organic pollutant in dyeing wastewater. The iron–carbon composite was found to be the most effective catalyst, and 99.63 ± 1 % of decolorization and 79.86 ± 2 % of COD removal can be achieved. The addition of sodium chloride reduced catalytic efficacies of sponge iron and iron–carbon composite slightly, but promoted those of chalcopyrite and pyrite. Furthermore, the stability and reusability of catalysts were examined and insignificant reduction on catalytic activity was observed for 5 cycles of electro-Fenton processes.

Catalytic activity comparison of typical iron-bearing particle electrodes in heterogeneous electro-Fenton oxidation processes

The impact of sodium salt on kerosene contaminated soil washing with surfactants was investigated The results indicated that sodium silicate greatly enhanced the washing efficiency of SDS Sodium tartrate can largely enhance the washing efficiency of SDBS and Brij35 Sodium salts can enhance the washing efficiency on kerosene contaminated with TX-100 No significant differences were observed between different sodium salts Sodium salt of humic acid and sodium silicate had similar enhancement on kerosene contaminated soil washing with saponin Sodium humate can be a better choice since its application can also improve soil quality The enhancement of sodium silicate on kerosene contaminated soil washing with Tw-80 increased with the increase of Tw-80 dosage However, the impact of sodium chloride and sodium tartrate was opposite to sodium silicate Sodium salts can reduce surface tension and critical micelle concentration of ionic surfactants to enhance the washing Sodium salts can also reduce re-adsorption of oil to soil with nonionic surfactants to enhance the washing Kerosene contamination can increase the contact angle of soil, which indicated the increase of hydrophilicity of soil Washing with surfactants can reduce the hydrophilicitiy of soil according to contact angle measurement, which indicated that kerosene contaminated soil remediation with surfactant can also benefit nutrient and water transportation in the contaminated soil

Strengthening Effects of Sodium Salts on Washing Kerosene Contaminated Soil with Surfactants

The utility model discloses an useless paint recovery unit in coating line spray booth, including hang between spraying work piece and cascade curtain, paint's the metal baffle of splashing can the entrapment atomizes, set up the paint collecting vat in the below of above -mentioned metal baffle, the utility model provides an useless paint recovery unit in coating line spray booth, baffle simple structure, the preparation of being convenient for, the useless paint of atomizing is efficient in the entrapment spray booth, installs and use portably, in the spraying room of the work piece of not unidimensional and shape separates, the utility model discloses a technique can effectively avoid paint by direct spraying at the cascade curtain to reduce the cascade drainage by paint pollution degree.

Huang Zhaolu

Papers

Comparison of heavy metal removals from aqueous solutions by chemical precipitation and characteristics of precipitates

Bimetallic Au-decorated Pd catalyst for the liquid phase hydrodechlorination of 2,4-dichlorophenol

Catalytic activity comparison of typical iron-bearing particle electrodes in heterogeneous electro-Fenton oxidation processes

Strengthening Effects of Sodium Salts on Washing Kerosene Contaminated Soil with Surfactants

Useless paint recovery unit in coating line spray booth