The high performance of non-free Fe in the electro-Fenton system has been rarely reported. Herein, such performance was observed using rod-shaped erdite for PMS activation in an electric field. Erdite was synthesised at 90 °C with the direct recycling of waste waterwork sludge. It had one-dimensional structure of the (FeS2)nn– group and was spontaneously hydrolysed in neutral water to release Fe/S-bearing colloid, but it contributed to the removal of 1.5 % p-nitrophenol only. The erdite hydrolysis was inhibited in the electric field but continued by adding PMS. Free radicals of •OH and SO4•− were generated. The removal efficiency of p-nitrophenol increased to 44.6 % by adding erdite/PMS and to 98.7 % in the presence of erdite/PMS in the electric filed, which was more than two times of the electro-Fenton reaction with ferrous halite or pyrite. Less than 25 mg/L free Fe was released into water by adding erdite, but 180 mg/L of that was released by adding ferrous halite. Thus, non-free Fe played a key role to activate PMS in three steps: (1) the involvement of structural Fe to ferric Fe by PMS activation; (2) the enhanced attachment of ferric Fe as non-free Fe on colloid/erdite in the electric field; (3) the reduction of ferric Fe into ferrous Fe by adjacent S in colloid/erdite. The Tafel and open-circuit voltage tests showed that the electric field stabilised the (FeS2)nn– group to terminate the hydrolysis of Fe-S bond and accelerated the attachment and the reduction of ferric Fe as the erdite hydrolysis continued by PMS. In summary, electric field and structural S of Fe/S-bearing colloid had synergistic effect on the cycling of non-free Fe2+/Fe3+ for enhancing PMS activation. 

Non-free Fe dominated PMS activation for enhancing electro-Fenton efficiency in neutral wastewater

One-step extraction of high-purity CuCl2·2H2O from copper-containing electroplating sludge based on the directional phase conversion.

XRD (X-ray diffraction), XRF (X-ray fluorescence), TG (thermogravimetry), FT-IES (Fourier transform infrared emission spectroscopy), FESEM (field emission scanning electron microscope), TEM (transmission electron microscope) and nitrogen–adsorption–desorption analysis were used to characterize the composition and thermal evolution of the structure of natural goethite. The in situ FT-IES demonstrated the start temperature (250 °C) of the transformation of natural goethite to hematite and the thermodynamic stability of protohematite between 250 and 600 °C. The heated products showed a topotactic relationship to the original mineral based on SEM analysis. Finally, the nitrogen–adsorption–desorption isotherm provided the variation of surface area and pore size distribution as a function of temperature. The surface area displayed a remarkable increase up to 350 °C, and then decreased above this temperature. The significant increase in surface area was attributed to the formation of regularly arranged slit-shaped micropores running parallel to elongated direction of hematite microcrystal. The main pore size varied from 0.99 nm to 3.5 nm when heating temperature increases from 300 to 400 °C. The hematite derived from heating goethite possesses high surface area and favors the possible application of hematite as an adsorbent as well as catalyst carrier.

Thermal treatment of natural goethite : thermal transformation and physical properties

Stepwise extraction of Fe, Al, Ca, and Zn: A green route to recycle raw electroplating sludge.

An efficient and economical treatment technology for heavy metal removal from the electroplating wastewaters is needed for the water purification. Therefore, pure cellulosic materials were derived from two waste fiber (pandanus fruit and durian rind) and conversion of the cellulose into the poly(acrylonitrile)-grafted material was accomplished by free radical grafting system. Thereafter, poly(amidoxime) ligand was produced from the grafted materials. Sorption capacity (qe) of several toxic metals ions was found to be high, e.g., copper capacity (qe) was 298.4 mg g−1 at pH 6. In fact, other metal ions, such as cobalt chromium and nickel also demonstrated significant sorption capacity at pH 6. Sorption mechanism played acceptable meet with pseudo second-order rate of kinetic pattern due to the satisfactory correlation with the experimental sorption values. A significant correlation coefficient (R2 > 0.99) with Langmuir model isotherm showed the single or monolayer sorption occurred on the surfaces. The reusability study showed that the polymer ligand can be useful up to six cycles with minimum loss (7%) of efficiency and can be used in the extraction of toxic metal ions present in the wastewaters. Therefore, two types of electroplating wastewater were used in this study, one containing high concentration of copper (23 ppm) and iron (32 ppm) with trace level of others heavy metals (IWS 1) and another containing high concentration of copper (85.7 ppm) only with trace level of others heavy metals (IWS 2). This polymeric ligand showed acceptable removal magnitude, up to 98% of toxic metal ions can be removed from electroplating wastewater.

https://www.mdpi.com/2073-4441/13/9/1260/pdf

Heavy metals removal from electroplating wastewater by waste fiber-based poly(amidoxime) ligand

Electroplating sludge is a hazardous waste produced in plating and metallurgical processes which is commonly disposed of in safety landfills. In this work, electroplating sludge containing 25.6% Fe and 5.5% Co (named S1) and another containing 36.8% Fe and 7.8% Cr (S2) were recycled for the preparation of erdite-bearing particles via a facile hydrothermal route with only the addition of Na2S·9H2O. In the sludges, Fe-containing compounds were weakly crystallized and spontaneously converted to short rod-like erdite particles (SP1) in the presence of Co or long nanorod (SP2) particles with a diameter of 100 nm and length of 0.5–1.5 μm in the presence of Cr. The two products, SP1 and SP2, were applied in electroplating wastewater treatment, in which a small portion of Co in SP1 was released in wastewater, whereas Cr in SP2 was not. Adding 0.3 g/L SP2 resulted in the removal of 99.7% of Zn, 99.4% of Cu, 37.9% of Ni and 53.3% of Co in the electroplating wastewater, with residues at concentrations of 0.007, 0.003, 0.33, 0.09 and 0.002 mg/L, respectively. Thus, the treated electroplating wastewater met the discharge standard for electroplating wastewater in China. These removal efficiencies were higher than those achieved using powdered activated carbon, polyaluminum chloride, polyferric sulfate or pure Na2S·9H2O reagent. With the method, waste electroplating sludge was recycled as nanorod erdite-bearing particles which showed superior efficiency in electroplating wastewater treatment.

https://www.mdpi.com/2073-4441/12/4/1027/pdf

Upcycling of Electroplating Sludge to Prepare Erdite-Bearing Nanorods for the Adsorption of Heavy Metals from Electroplating Wastewater Effluent

In situ conversion of goethite to erdite nanorods to improve the performance of doxycycline hydrochloride adsorption

Water is a vital, finite resource whose quantity and quality are deteriorating as the world population increases. The current study aims to investigate the concentration of heavy metals (HM) in surface water for irrigation purposes with associated human health risks and pollution sources near the marble industry in Malakand, Pakistan. Twenty-seven water samples were randomly collected and analyzed for HM concentration by inductively coupled plasma‒optical emission spectrometry (ICP‒OES). pH, electrical conductivity (EC), total dissolved solids (TDS), biological oxygen demand (BOD), and chemical oxygen demand (COD) were measured using standard methods of American Public Health Association (APHA). Irrigation suitability was assessed using specific water quality parameters. The associated health risks from ingestion and dermal exposure to heavy metals were calculated by USEPA health risk indices. Pollution sources and spatial distribution mapping were studied using compositional data analysis (CoDa) and the application of a geographic information system (GIS) to understand the changing behavior of heavy metals in surface waters. The concentrations of BOD (89%), COD (89%), Al (89%), Ca (89%), Cr (56%), Cu (78%), Fe (56%), K (34%) Mg (23%), Mn (56%), Na (89%), Ni (56%), P (89%), and Zn (11%) exceeded the safety limits of National Environmental Quality standards (NEQs) of Pakistan. The results of Kelly’s ratio (KR) classified surface water as unsuitable for irrigation. The average daily doses (ADD, mg/kg/day) for Al, Cu, Cr, Fe, Mn, Ni, and Zn were higher in children than in adults. The hazard index (HI) for children and adults was above the threshold (HI > 1), indicating a significant risk of non-carcinogenic toxicity. The carcinogenic risk values for Cr and Ni were above the USEPA limit (1 × 10−6 to 1 × 10−4), suggesting a potential carcinogenic risk for the target population. Principal component analysis (PCA), biplot (CLR), and the CoDa-dendrogram allowed for the identification of elemental associations, and their potential source was anthropogenic rather than natural in origin. Regular monitoring and phytoremediation strategies are proposed to safeguard crops and human health.

/pdf/irrigation-suitability-health-risk-assessment-and-source-1id9z0c2.pdf

Irrigation suitability, health risk assessment and source apportionment of heavy metals in surface water used for irrigation near marble industry in Malakand, Pakistan

Aggregate is a worldwide raw material used for various construction purposes which are obtained from geological material through drilling, blasting, mining, and river derived. This study has been focused on river Panjkora and Kunai-derived aggregates which are natural sources of aggregate used for various construction purposes in Dir (Lower). Field observation and detailed petrographic studies of representative samples reveal that rivers Panjkora and Kunai pass from different lithological units of granite, gabbroic, and amphibolite. Petrographically, the granitic rocks of the study area are consisting of alkali feldspar, quartz, and plagioclase feldspar. Minor accessory minerals in granite were hornblende, biotite, epidote, rutile, zircon, and ore minerals. The gabbroic rocks are consisting of pyroxene, plagioclase, and minor to accessory minerals including biotite, sphene, rutile, epidote, and ore minerals. The main mineral phases in amphibolites are hornblende, plagioclase, and a minor amount of quartz, sphene, and ore minerals. Gneissose fabric has developed in amphibolite refers to its banded nature. The minor mineral phases of amphibolite include epidote, ore minerals, and garnet. The feldspar alteration in granite is in the form of sericitization and normal zoning. The physical properties of river Panjkora and Kunai float i.e., water absorption, specific gravity, fine modulus, loss Angeles and soundness were within the range. Both petrographic and geotechnical properties suggested that these aggregates are suitable to be used as coarse aggregate in concrete. These must be present in the recommendation section at the end. 

The Effect of Mineral Composition, Microstructure on Physical Properties of Aggregate from River Punjkora and Kunai, Dir (Lower), Khyber Pakhtunkhwa, Pakistan

Asghar Khan

Papers

Upcycling of Electroplating Sludge to Prepare Erdite-Bearing Nanorods for the Adsorption of Heavy Metals from Electroplating Wastewater Effluent

In situ conversion of goethite to erdite nanorods to improve the performance of doxycycline hydrochloride adsorption

Irrigation suitability, health risk assessment and source apportionment of heavy metals in surface water used for irrigation near marble industry in Malakand, Pakistan

The Effect of Mineral Composition, Microstructure on Physical Properties of Aggregate from River Punjkora and Kunai, Dir (Lower), Khyber Pakhtunkhwa, Pakistan